Clinical Microbiology Made Ridiculously Simple �Medmaster CHAPTER 2

Peface

A well-developed knowledge of clinical microbiology is 4) Create a conceptual, organized approach to the or- critical for the practicing physician in any medical field. ganisms studied so the student relies less on memory Bacteria, viruses, and protozoans have no respect for and more on logical pathophysiology. the distinction between ophthalmology, pediatrics, The text has been updated to include current infor- trauma surgery, or geriatric medicine. As a physician mation on rapidly developing topics, such as HIV and you will be faced daily with the concepts of microbial AIDS (vaccine efforts and all the new anti-HIV medica- disease and antimicrobial therapy. Microbiology is one tions), Ebola virus, Hantavirus, E. outbreaks, Mad of the few courses where much of the "minutia" is regu- larly used by the practicing physician. Cow Disease, and brand-new antimicrobial antibiotics. This book attempts to facilitate the learning of mi- The mnemonics and cartoons in this book do not in- tend disrespect for any particular patient population or crobiology by presenting the information in a clear and entertaining manner brimming with memory aids. racial or ethnic group but are solely presented as mem- Our approach has been to: ory devices to assist in the learning of a complex and important medical subject. 1) Write in a conversational style for rapid assimi- We welcome suggestions for future editions. lation. 2) Include numerous figures serving as "visual mem- MARK GLADWIN, MD ory tools" and summary charts at the end of each chap- BILL TRATTLER, MD ter. These can be used for "cram sessions" after the concepts have been studied in the text. 3) Concentrate more on clinical and infectious disease issues that are both interesting and vital to the actual practice of medicine.

D CONTENTS

Preface v

PART 1 1 1 BACTERIAL TAXONOMY 1 2 CELL STRUCTURES, VIRULENCE FACTORS, and TOXINS 8 3 BACTERIAL SE( GENETICS 16

GRAM-POSITIVE BACTERIA 22 4 STREPTOCOCCUS 22 5 STAPHYLOCOCCUS 31 6 BACILLUS and CLOSTRIDIUM (SPORE-FORMING RODS) 38 7 CORYNEBACTERIUM and LISTERIA (NON-SPORE-FORMING RODS) 45

GRAM-NEGATNE BACTERIA 49 8 NEISSERIA 49 9 THE ENTERICS 54 10 HAEMOPHILUS, BORDETELLA, and LEGIONELLA 68 11 YERSINIA, FRANCISELLA, BRUCELLA, and PASTEURELLA 73 12 CHLAMYDIA, RICKETTSIA, and FRIENDS 78 13 SPIROCHETES 91

ACID-FAST BACTERIA 102 14 MYCOBACTERIUM 102

BACTERIA WITHOUT CELL WALLS 111 15 MYCOPLASMA 111

ANTI-BACTERIAL MEDICATIONS 114 16 PENICILLIN FAMILY ANTIBIOTICS 114 17 ANTI-RIBOSOMAL ANTIBIOTICS 125 18 ANTI-TB and ANTI-LEPROSY ANTIBIOTICS 133 19 MISCELLANEOUS ANTIBIOTICS 139

PART 2. FUNGI 144 20 THE FUNGI 144 21 ANTI-FUNGAL MEDICATIONS 155

PART 3 161 22 VIRAL REPLICATION and TAXONOMY 161 23 ORTHOMYXO and PARAMYXOVIRIDAE 172 24 HEPATITIS VIRIDAE 180 25 RETROVIRIDAE, HIV, and AIDS 190 26 HERPESVIRIDAE 204 27 REST OF THE DNA VIRUSES 209 28 REST OF THE RNA VIRUSES 214 29 ANTI-VIRAL MEDICATIONS 224

PART 4. PARASITES 231 30 PROTOZOANS 231 31 HELMINTHS 248

vi PART 5. VERY STRANGE CRITTERS 265 32 PRIONS (contributing author: Hans Henrik Larsen, M.D.) 265 PART 6. 33 ANTIMICROBIAL RESISTANCE: ONE STEP TOWARD THE POST-ANTIBIOTIC ERA? (contributing author: Earnest Alexander, Pharm.D.) 269 BIOTERRORISM DEFENSE UPDATES: http://www.medmaster.netBioterrorismDefense.html

Peface

D CONTENTS

Preface v

PART 1 1 1 BACTERIAL TAXONOMY 1 2 CELL STRUCTURES, VIRULENCE FACTORS, and TOXINS 8 3 BACTERIAL SE( GENETICS 16

GRAM-POSITIVE BACTERIA 22 4 STREPTOCOCCUS 22 5 STAPHYLOCOCCUS 31 6 BACILLUS and CLOSTRIDIUM (SPORE-FORMING RODS) 38 7 CORYNEBACTERIUM and LISTERIA (NON-SPORE-FORMING RODS) 45

ACID-FAST BACTERIA 102 14 MYCOBACTERIUM 102

BACTERIA WITHOUT CELL WALLS 111 15 MYCOPLASMA 111

ANTI-BACTERIAL MEDICATIONS 114 16 PENICILLIN FAMILY ANTIBIOTICS 114 17 ANTI-RIBOSOMAL ANTIBIOTICS 125 18 ANTI-TB and ANTI-LEPROSY ANTIBIOTICS 133 19 MISCELLANEOUS ANTIBIOTICS 139

PART 2. FUNGI 144 20 THE FUNGI 144 21 ANTI-FUNGAL MEDICATIONS 155

PART 4. PARASITES 231 30 PROTOZOANS 231 31 HELMINTHS 248

CHAPTER 1. BACTERIAL TAXONOMY

All organisms have a name consisting of two parts: the genus followed by the species (i.e., Homo sapiens). Bac- DISACCHARIDE teria have been grouped and named primarily on their morphological and biochemical/metabolic differences. However, bacteria are now also being classified according to their immunologic and genetic characteristics. This chapter focuses on the Gram stain, bacterial morphology, and metabolic characteristics, all of which enable the clinician to rapidly determine the organism causing a patient's infection.

GRAM STAIN Because bacteria are colorless and usually invisible to light microscopy, colorful stains have been developed to visualize them. The most useful is the Gram stain, which separates organisms into 2 groups: gram-positive bugs and gram-negative bugs. This stain also allows the clinician to determine whether the organism is round or rod-shaped. For any stain you must first smear the substance to be stained (sputum, pus, etc.) onto a slide and then heat AMINO ACIDS it to fix the bacteria on the slide. There are 4 steps to the Gram stain: 1) Pour on crystal violet stain (a blue dye) and wait 60 seconds. Fige 1-1 2) Wash off with water and flood with iodine solu- tion. Wait 60 seconds. Both gram-positive and gram-negative organisms 3) Wash off with water and then "decolorize" with have more than 1 layer protecting their cytoplasm and 95% alcohol. nucleus from the extracellular environment, unlike an- 4) Finally, counter-stain with safranin (a red dye). imal cells, which have only a single cytoplasmic mem- Wait 30 seconds and wash off with water. brane composed of a phospholipid bilayer. The layer just outside the bacterial cytoplasmic membrane is the pep- When the slide is studied microscopically, cells that tidoglycan layer or cell wall. It is present in both absorb the crystal violet and hold onto it will appear gram-positive and gram-negative organisms. blue. These are called gram-positive organisms. How- ever, if the crystal violet is washed off by the alcohol, Fig. 1-1. The peptidoglycan layer or cell wall is these cells will absorb the safranin and appear red. composed of repeating disaccharides with 4 amino acids These are called gram-negative organisms. in a side chain extending from each disaccharide. Gram-positive = BLUE Fig. 1-2. The amino-acid chains of the peptidoglycan I'm positively BLUE over you!! covalently bind to other amino acids from neighboring chains. This results in a stable cross-linked structure. Gram-negative = RED The enzyme that catalyzes the formation of this linkage No (negative) RED commies!! is called transpeptidase and is located in the inner cytoplasmic membrane. The antibiotic penicillin binds to The different stains are the result of differences in the and inhibits this enzyme. For this reason the enzyme is cell walls of gram-positive and gram-negative bacteria. also called penicillin binding protein (see page 114).

1 CHAPTER 1. BACTERIAL TAXONOMY

Figure 1-2 ( ) - . A - . I , - - . Figure 1-3 Fig. 1-5. T - S , . L - Fig. 1-3. T - , 1) - - 2) . 3) I , - . I , - . - . T ( - ) - Fig. 1-4. T - . G- - - - , , , . . T T - - . T . T . T - ,

Figure 1-4

2 CHAPTER 1. BACTERIAL TAXONOMY

GRAM-NEGATIVE CELL ENVELOPE

OUTER MEMBRANE

MUREIN LIPOPROTEIN PEPTIDOGLYCAN LAYER (CELL WALL) PERIPLASMIC SPACE

CYTOPLASMIC MEMBRANE

EMBEDDED PROTEINS

Figure 1-5

lipoprotein called murein lipoprotein. This lipoprotein is important because it originates from the peptidoglycan layer and extends outward to bind the unique third outer membrane. This last membrane is similar to other cell membranes in that it is composed of two layers of phospholipid (bilayer) with hydrophobic tails in the center. What makes it unique is that the outermost portion of the bilayer contains lipopolysaccharide (LPS). Fig. 1-6. Lipopolysaccharide (LPS) is composed of 3 covalently linked components:

1) Outer carbohydrate chains of 1-50 oligosaccha- ride units that extend into the surrounding media. These differ from one organism to another and are anti- Figure 1-6 genic determinants. This part is called the 0-specific

3 CHAPTER 1. BACTERIAL TAXONOMY

Gam-Poiie Cell Gam-Negaie Cell 2 Lae: 3 Lae: 1. Inne coplamic membane 1. Inne coplamic membane 2. Oe hick pepidoglcan lae 2. Thin pepidoglcan lae (60-100% pepidoglcan) (5- 10% pepidoglcan) 3. Oe membane ih lipopolacchaide (LPS) Lo lipid conen High lipid conen NO endotoxin (except Listeria Endooin (LPS) - lipid A monocytogenes) NO peiplamic pace Peiplamic pace NO poin channel Poin channel Vlneable o lome and Reian o lome and penicillin aack penicillin aack Figure 1-7 DIFFERENCES BETWEEN GRAM- -POSITIVE AND GRAM-NEGATIVE ORGANISMS side chain or the 0-antigen. Think of O for Outer to dally dissolved by alcohol, thus washing out the crystal help remember this. violet and allowing the safranin counterstain to take. The center part is a water soluble core polysac- 2) Summary of differences between gram- charide. Fig. 1-7. positive and gram-negative bacteria. 3) Interior to the core polysaccharide is the third component, lipid A, which is a disaccharide with mul- BACTERIAL MORPHOLOGY tiple fatty acid tails reaching into the membrane. Lipid A is toxic to humans and is known as the gram-negative Bacteria have 4 major shapes: endotoxin. When bacterial cells are lysed by our effi- ciently working immune system, fragments of mem- 1) Cocci: spherical. brane containing lipid A are released into the 2) Bacilli: rods. Short bacilli are called coc- circulation, causing fever, diarrhea, and possibly fatal cobacilli. endotoxic shock (also called septic shock). 3) Spiral forms: comma-shaped, S-shaped, or spiral-shaped. Embedded in the gram-negative outer membrane are 4) Pleomorphic: lacking a distinct shape (like jello). porin proteins, which allow passage of nutrients. These The different shaped creatures organize together into are also unique to gram-negative organisms. more complex patterns, such as pairs (diplococci), clus- What does this mean clinically? ters, strips, and single bacteria with flagella. The differences between gram-positive and gram- Fig. 1-8. Bacterial morphology. negative organisms result in varied interactions with SO, WHAT ARE THE NAMES?!!!! the environment. The gram-positive thickly meshed peptidoglycan layer does not block diffusion of low mol- Gram-Positive ecular weight compounds, so substances that damage the cytoplasmic membrane (such as antibiotics, dyes, Start by remembering that there are 6 classic gram- and detergents) can pass through. However, the gram- positive bugs that cause disease in humans, and basi- negative outer lipopolysaccharide-containing cell mem- cally every other organism is gram-negative. brane blocks the passage of these substances to the Of the gram-positives, 2 are cocci, and the other 4 are peptidoglycan layer and sensitive inner cytoplasmic rod-shaped (bacilli). membrane. Therefore, antibiotics and chemicals that The 2 gram-positive cocci both have the word coccus attempt to attack the peptidoglycan cell wall (such as in their names: penicillins and lysozyme) are unable to pass through. 1) Streptococcus forms strips of cocci. Interestingly, the crystal violet stain used for Gram 2) Staphylococcus forms clusters of cocci. staining is a large dye complex that is trapped in the thick, cross-linked gram-positive cell wall, resulting in Two of the 4 gram-positive rods produce spores the gram-positive blue stain. The outer lipid-containing (spheres that protect a dormant bacterium from the cell membrane of the gram-negative organisms is par- harsh environment). They are:

4 CHAPTER 1. BACTERIAL TAXONOMY

Gam-Negaie COCCI Of the gram-negative organisms, there is only one group of gram-negative cocci. It is actually a diplococcus (looks like 2 coffee beans kissing): Neisseria. There is also just 1 group of spiral-shaped organisms: BACILLI o RODS the Spirochetes. This group includes the bacterium Tre- ponema pallidum, which causes syphilis. The rest are gram-negative rods or pleomorphic.

SPIRAL Exceptions: 1) Mycobacteria are weakly gram-positive but stain better with a special stain called the acid-fast COMMA stain (See Chapter 14). This special group includes organisms that cause tuberculosis and leprosy. 2) Spirochetes have a gram-negative cell wall S-SHAPED but are too small to be seen with the light microscope and so must be visualized with a special darkfield microscope. 3) Mycoplasma do not have a cell wall. They only have a simple cell membrane, so they are neither gram- positive nor gram-negative. PLEOMORPHIC Fig. 1-9. Summary of morphological differences among the bacteria.

CLUSTERS CYTOPLASMIC STRUCTURES Bacterial DNA usually consists of a single circle of double-stranded DNA. Smaller adjacent circles of STRIPS double-stranded DNA are called plasmids; they often contain antibiotic resistance genes. Ribosomes are composed of protein and RNA and are involved in the DIPLOCOCCI translation process, during the synthesis of proteins. Bacteria, which are procaryotes, have smaller ribosomes (70S) than animals (80S), which are eucaryotes. WITH FLAGELLA Bacterial ribosomes consist of 2 subunits, a large subunit (50S) and a small subunit (30S). These numbers re- late to the rate of sedimentation. Antibiotics, such as erythromycin and tetracycline, have been developed that attack like magic bullets. They inhibit protein synthesis preferentially at the bacterial ribosomal subunits while leaving the animal ribosomes alone. Erythromy- cin works at the 50S subunit, while tetracycline blocks Fige 1-8 protein synthesis at the 30S subunit. 3) Bacillus 4) Clostridium METABOLIC CHARACTERISTICS The last 2 gram-positive rods do not form spores: Bacteria can be divided into groups based on their metabolic properties. Two important properties include: 5) Cornebacterium 1) how the organism deals with oxygen, and 2) what the 6) Listeria, which surprisingly has endotoxin-sur- organism uses as a carbon and energy source. Other prising because ALL other organisms with endotoxin properties include the different metabolic end-products are gram-negative. that bacteria produce such as acid and gas.

5 CHAPTER 1. BACTERIAL TAXONOMY

MORPHOLOGY GRAM-POSITIVE GRAM-NEGATIVE Cicla (Cocc) Streptococcus Neisseria Staphylococcus Rod (Bacillus) Corynebacterium ENTERICS (live in the GI tract): Listeria Escherichia coli Bacillus Shigella Clostridium Salmonella • Yersinia Klebsiella Proteus Enterobacter Mycobacterium (acid-fast) Seaia Vibrio Campylobacter Helicobacter Pseudomonas BacteroIdes (anaerobic) Haemophilus Bordetella Legionella Yersinia Francisella Brucella Pasteurella Gardnerella Spiral Spirochetes: Treponema Borrelia Leptospira Branching filamentous growth Actinomyces (anaerobic) (like fungi) Nocardia (partially acid-fast) Pleomorphic Chlamydia Rickettsiae No cell all Mycoplasma Figure 1-9 MORPHOLOGICAL DIFFERENCES AMONG THE BACTERIA

Oxygen 3) Speoide dimae breaks down the superoxide radical in the following reaction: How bacteria deal with oxygen is a major factor in their classification. Molecular oxygen is very reactive, and when it snatches up electrons, it can form hydrogen peroxide (H2O2), superoxide radicals (02i, and a hy- Bacteria are classified on a continuum. At one end are droxyl radical (OH - ). All of these are toxic unless bro- those that love oxygen, have all the preceding protective ken down. In fact, our very own macrophages produce enzymes, and cannot live without oxygen. On the oppo- these oxygen radicals to pour over bacteria. There are 3 site end are bacteria which have no enzymes and pretty enzymes that some bacteria possess to break down much kick the bucket in the presence of oxygen: these oxygen products: 1) Obligae aeobe: These critters are just like us in that they use glycolysis, the Krebs TCA cycle, and the 1) Caalae breaks down hydrogen peroxide in the electron transport chain with oxygen as the final elec- following reaction: tron acceptor. These guys have all the above enzymes. 2) Faclaie anaeobe: Dont let this name fool you! These bacteria are aerobic. They use oxygen as an 2) Peoidae also breaks down hydrogen peroxide. electron acceptor in their electron transfer chain and

6 CHAPTER 1. BACTERIAL TAXONOMY

OBLIGATE FACULTATIVE MICROAEROPHILIC OBLIGATE AEROBES ANAEROBES ANAEROBES Gram-positive Nocardia Staphylococcus Streptococcus Clostridium (eakl acid-fast) Bacillus anthracis Bacillus cereus Corynebacterium Listeria Actinomyces Gram-negative Neisseria Most other gram- Spirochetes Bacteroides Pseudomonas negative rods Treponema Bordetella Borrelia Legionella Leptospira Brucella Campylobacter Acid-fast Mycobacterium Nocardia No cell all Mycoplasma

Chlamydia and Rickettsia do no hae he meabolic machine o ilie ogen. The ae eneg paaie, and m eal hei ho ATP. Figure 1-10 OXYGEN SPECTRUM

have catalase and superoxide dismutase. The only dif- erotrophs. All the medically important bacteria are ference is that they can grow in the absence of oxygen chemoheterotrophs because they use chemical and by using fermentation for energy. Thus they have the organic compounds, such as glucose, for energy. faculty to be anaerobic but prefer aerobic conditions. Fermentation (glycolysis) is used by many bacteria Phis is similar to the switch to anaerobic glycolysis that for oxygen metabolism. In fermentation, glucose is bro- human muscle cells undergo during sprinting. ken down to pyruvic acid, yielding ATP directly. There 3) Microaerophilic bacteria (also called aero- are different pathways for the breakdown of glucose to tolerant anaerobes): These bacteria use fermentation pyruvate, but the most common is the Embden- and have no electron transport system. They can toler- Meyerhof pathway. This is the pathway of glycolysis ate low amounts of oxygen because they have superox- that we have all studied in biochemistry. Following fer- ide dismutase (but they have no catalase). mentation the pyruvate must be broken down, and the 4) Obligate anaerobes: These guys hate oxygen different end products formed in this process can be and have no enzymes to defend against it. When you are used to classify bacteria. Lactic acid, ethanol, propionic working on the hospital ward, you will often draw blood acid, butyric acid, acetone, and other mixed acids can for culture. You will put the blood into 2 bottles for be formed. growth. One of these is an anaerobic growth media with Respiration is used with the aerobic and facultative no oxygen in it! anaerobic organisms. Respiration includes glycolysis, Krebs tricarboxylic-acid cycle, and the electron trans- Fig. 1-10. The oxygen spectrum of the major bacterial port chain coupled with oxidative phosphorylation. groups. These pathways combine to produce ATP. Obligate intracellular organisms are not capable Carbon and Energy Source of the metabolic pathways for ATP synthesis and thus Some organisms use light as an energy source (pho- must steal ATP from their host. These bacteria live in totrophs), and some use chemical compounds as an en- their host cell and cannot survive without the host. ergy source (chemotrophs). Of the organisms that use Further metabolic differences (such as sugar sources chemical sources, those that use inorganic sources, such used, end products formed, and the specific need for cer- as ammonium and sulfide, are called autotrophs. Oth- tain nutrients) figure in classifying bacteria and will be ers use organic carbon sources and are called het- discussed in the chapters covering specific organisms. CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

Figure 2-1

Virulent organisms are those that can cause disease. gradient or away from the gradient. This movement is The virulence of an organism is the degree of organism called chemotaxis. pathogenicity. Virulence depends on the presence of certain cell structures and on bacterial exotoxins and en- Fig. 2-2. Bacteria can have a single polar flagellum dotoxins, all of which are virulence factors. ( polar means at one end of the cell) as is the case with Vibrio cholera, or many peritrichous flagella (all around the cell) as is the case with Escherichia coli and CELL STRUCTURES AS VIRULENCE Proteus mirabilis. Shigella does not have flagella. FACTORS Pili Flagella Pili (also called fimbriae) are straight filaments Fig. 2-1. Flagella are protein filaments that extend arising from the bacterial cell wall, making the bac- like long tails from the cell membranes of certain gram- terium look like a porcupine. positive and gram-negative bacteria. These tails, which are several times the length of the bacterial cell, move Fig. 2-3. Pili are much shorter than flagella and do the bacteria around. The flagellum is affixed to the bac- not move. Pili can serve as adherence factors (in which teria by a basal body. The basal body spans through case they are called adhesins). Many bacteria possess the entire cell wall, binding to the inner and outer cell adhesins that are vital to their ability to cause disease. membrane in gram-negative bacteria and to the inner For example, Neisseria gonorrhea has pili that allow it membrane in gram-positive bugs (the gram-positive to bind to cervical cells and buccal cells to cause gonor- bacteria don't have an outer membrane). The basal body rhea. Escherichia coli and Campylobacter jejuni cannot spins around and spins the flagellum. This causes the cause diarrhea without their adhesins to bind to the in- bacterial flagella to undulate in a coordinated manner testinal epithelium, and Bordetella pertussis uses its to move the bacteria toward a chemical concentration adhesin to bind to ciliated respiratory cells and cause

8 CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

whooping cough. Bacteria that do not produce these pili cannot grab hold of their victim; they lose their virulence and thus cannot infect humans. There are also special pili, discussed in the next chapter, called sex pili. Capsules

Capsules are protective walls that surround the cell membranes of gram-positive and gram-negative bacteria. They are usually composed of simple sugar residues. Bacteria secrete these sugar moieties, which then coat their outer wall. One bacterium, Bacillus anthracis, is unique in that its capsule is made up of amino acid residues.

Fig. 2-4. Capsules enable bacteria to be more virulent because macrophages and neutrophils are unable to phagocytize the encapsulated buggers. For example, Streptococcus pneumoniae has a capsule. When Figure 2-2 grown on media, these encapsulated bacteria appear as smooth (S) colonies that cause rapid death when injected into mice. Some Streptococcus pneumoniae do not have capsules and appear as rough (R) colonies on agar.

Figure 2-3

9 CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

Figure 2-4

These rough colonies have lost their virulence and when injected into mice do not cause death.

Two important tests enable doctors to visualize capsules under the microscope and aid in identifying bacteria:

1) India ink stain: Because this stain is not taken up by the capsule, the capsule appears as a transparent halo around the cell. This test is used primarily to identify the fungus Cryptococcus. 2) Quellung reaction: The bacteria are mixed with antibodies that bind to the capsule. When these antibodies bind, the capsule swells with water, and this can be visualized microscopically. Figure 2-5 Antibodies directed against bacterial capsules protect that protects the individual against future infections us as they help our macrophages and neutrophils bind by this organism. to and eat the encapsulated bacteria. The process of antibodies binding to the capsule is called opsonization. Endospores

Fig. 2-5. Once the antibodies have bound to the Endospores are formed by only 2 genera of bacteria, bacterial capsule (opsoniation), the macrophage or both of which are gram-positive: the aerobic Bacillus neutrophil can then bind to the Fc portion of the anti- and the anaerobic Clostridium. body and gobble up the bacteria. A vaccine against Streptococcus pneumoniae contains antigens from the Fig. 2-6. Endospores are metabolically dormant 23 most common types of capsules. Immunization with forms of bacteria that are resistant to heat (boiling), this vaccine elicits an immune response against the cold, drying and chemical agents. They have a multi- capsular antigens and the production of antibodies layered protective coat consisting of:

10 CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

phagosome-lysosome fusion, thus escaping the hosts deadly hydrogen peroxide and superoxide radicals. In- side the cells these bacteria are safe from antibodies and other immune defenses.

FACULTATIVE INTRACELLULAR ORGANISMS 1. Listeria monoctogenes 2. Salmonella tphi 3. Yersinia 4. Francisella tularensis 5. Brucella 6. Legionella 7. Mcobacterium Figure 2-7

Fig. 2-7. Facultative intracellular organisms.

TOXINS Exotoxins

Exotoxins are proteins that are released by both gram-positive and gram-negative bacteria. They may cause many disease manifestations. Essentially, exotoxins are released by all the major gram-positive genera except for Listeria monoctogenes, which produces endotoxin. Gram-negative bacteria such as Vibrio cholera, Escherichia coli, and others can also excrete exotoxins. Severe diseases caused by bacterial exotoxins include anthrax (Saddam Husseins threatened germ warfare agent), botulism, tetanus, and cholera. Neurotoxins are exotoxins that act on the nerves or Figure 2-6 motor endplates to cause paralysis. Tetanus toxin and botulinum toxin are examples. Enterotoxins are exotoxins that act on the gas- A) A cell membrane trointestinal (GI) tract to cause diarrhea. Enterotoxins B) A thick peptidoglycan mesh inhibit NaCl resorption, activate NaCl secretion, or kill C) Another cell membrane intestinal epithelial cells. The common end result is D) A wall of keratin-like protein the osmotic pull of fluid into the intestine, which E) An outer layer called the exosporium causes diarrhea. The enterotoxins cause 2 disease manifestations: Spores form when there is a shortage of needed nutrients and can lie dormant for years. Surgical instru- 1) Infectious diarrhea: Bacteria colonize and bind ments are heated in an autoclave, which uses steam to the GI tract, continuously releasing their enterotox- under pressure, to 121C for 15 minutes, in order to en- ins locally. The diarrhea will continue until the bacteria sure the destruction of Clostridium and Bacillus spores. are destroyed by the immune system or antibiotics (or When the spore is exposed to a favorable nutrient or en- the patient dies secondary to dehydration). Examples: vironment, it becomes active again. Vibrio cholera, Escherichia coli, Campylobacter jejuni, and Shigella dysenteriae. Facultative Intracellular Organisms 2) Food poisoning: Bacteria grow in food and release enterotoxin in the food. The enterotoxin is in- Many bacteria are phagocytosed by the hosts gested resulting in diarrhea and vomiting for less than macrophages and neutrophils yet survive within these 24 hours. Examples: Bacillus cereus and Staphlococcus white blood cells unharmed!!! These bacteria inhibit aureus.

1 1 CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

Pyrogenic exotoxins stimulate the release of cy- To better understand septic shock, let us back up and tokines and can cause rash, fever, and toxic shock syn- review some terms. drome (see page 33). Examples: Staphylococcus aureus Bacteremia: This is simply bacteria in the blood- and Streptococcus pyogenes. stream. Bacteria can be detected by isolating the of- Tissue invasive exotoxins allow bacteria to defending critters in blood cultures. Bacteremia can occur stroy and tunnel through tissues. These include en- silently and without symptoms. Brushing your teeth re- zymes that destroy DNA, collagen, fibrin, NAD, red sults in transient bacteremia with few systemic conse- blood cells, and white blood cells. quences. Bacteremia can also trigger the immune Miscellaneous exotoxins, which are the principle system, resulting in sepsis and possibly death. virulence factors for many bacteria, can cause disease Sepsis: Sepsis refers to bacteremia that causes a sys- unique to the individual bacterium. Often the exact role temic immune response to the infection. This response of the exotoxin is poorly understood. can include high or low temperature, elevation of the white blood cell count, and fast heart rate or breathing Fig. 2-S. This chart gives many of the important exo- rate. Septic patients are described as "looking sick." toxins and compares their mechanisms of action. Glance Septic shock: Sepsis that results in dangerous drops over the chart now and return to it as you study indi- i n blood pressure and organ dysfunction is called septic vidual bacteria. shock. It is also referred to as endotoxic shock be- Fig. 2-9. Exotoxin subunits in Bacillus anthracis, cause endotoxin often triggers the immune response Clostridium botulinum, Clostridium tetani, Corynebac- that results in sepsis and shock. Since gram-positive terium diphtheriae, and Vibrio cholera. Their exotoxins bacteria and fungi can also trigger this adverse immune are all composed of 2 polypeptide subunits bound to- response, the term septic shock is more appropriate gether by disulfide bridges. One of these subunits and inclusive. (called B for binding or H for holding on) binds to the The chain of events that lead to sepsis and often target cell. The other subunit (called A for action or L death begins with a localized site of infection of gram- for laser) then enters the cell and exerts the toxic effect. negative or gram-positive bacteria or fungi. From this Picture these subunits as a key (B and H) and a gun (A site or from the blood (bacteremia), the organisms re- and L) bound together by disulfide bonds. The key opens lease structural components (such as endotoxin and/or the cell, and then the gun does its damage. exotoxin) that circulate in the bloodstream and stimulate immune cells such as macrophages and neutrophils. These cells, in response to the stimulus, Endotoxins release a host of proteins that are referred to as en- Remember from the last chapter that endotoxin is dogenous mediators of sepsis. lipid A, which is a piece of the outer membrane The most famous endogenous mediator of sepsis is lipopolysaccharide (LPS) of gram-negative bacteria (see tumor necrosis factor (TNF). TNF is also called Fig. 1-6). Lipid A/endotoxin is very toxic and is released cachectin because it is released from tumors, produc- when the bacterial cell undergoes lysis (destruction). ing a wasting (weight loss) syndrome, called cachexia, Endotoxin is also shed in steady amounts from living in cancer patients. Injecting TNF into experimental bacteria. Sometimes, treating a patient who has a gram- animals produces hypotension and death (septic shock). negative infection with antibiotics can worsen the pa- In sepsis, TNF triggers the release of the cytokine tient's condition because all the bacteria are lysed, interleukin-1 from macrophages and endothelial cells, releasing large quantities of endotoxin. Endotoxin dif- which in turn triggers the release of other cytokines fers from exotoxin in that it is not a protein ex- and prostaglandins. This churning maelstrom of medi- creted from cells, but rather is a normal part of ators at first defends the body against the offending the outer membrane that sort of sheds off, espe- microorganisms, but ultimately turns against the body. cially during lysis. Endotoxin is ONLY present in The mediators act on the blood vessels and organs gram-negative bacteria with one exception: Listeria to produce vasodilatation, hypotension, and organ sys- monocytogenes, a gram-positive bacteria, has endotoxin. tem dysfunction. The mortality rate for septic shock is high: up to 40% Septic Shock of patients will die, even with intensive care and antibiotic therapy. For every organ system that fails the Septic shock (endotoxic shock) is a common and mortality rises. Usually two organs are involved (vas- deadly response to both gram-negative and gram- cular system with hypotension and lungs with hypoxia) positive infection. In fact, septic shock is the number and the mortality rate is about 40%. For each addi- one cause of death in intensive care units and the 13th tional organ failure (renal failure, etc.) add 15-20% most common cause of death in the U.S. (Parrillo, 1990). mortality!

12 Figure 2-8 EXOTOXINS Figure 2-8 (continued) M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple MedMaster CHAPTER 2. CELL STRUCTURES, VIRULENCE FACTORS AND TOXINS

Figure 2-9

ORGAN SYSTEM EFFECT ON ORGAN SYSTEM DAMAGING EFFECT ON BODY Vascular system Vasodilation 1. Decreased blood pressure 2. Organ hypoperfusion Heart Myocardial depression 1. Decreased cardiac output 2. Decreased blood pressure 3. Organ hypoperfusion Kidneys Acute renal failure 1. Decreased urine output 2. Volume overload 3. Accumulation of toxins Lungs Adult respiratory distress syndrome Hypoxia Liver Hepatic failure 1. Accumulation of metabolic toxins 2. Hepatic encephalopathy Brain Encephalopathy Alteration in mental status Coagulation system Disseminated intravascular coagulation 1. Clotting 2. Bleeding

Figure 2-10 EFFECTS OF SEPTIC SHOCK

Treatment host of other investigational agents (tumor necrosis factor soluble receptor, nitric oxide antagonists, and The most important principle of treatment is to find antioxidant compounds), have met with disappointing the site of infection and the bug responsible and eradi- results. Most of these treatments have failed to reduce cate it! The lung is the most common site (pneumonia) mortality in clinical trials. followed by the abdomen and urinary tract. In one-third of cases a site of infection is not identified. Antibiotic therapy is critical with a 10 to 15 fold increased mortal- Fig. 2-10. The end organ effects of septic shock. ity when antibiotics are delayed. Even while working up the site of infection you should start broad coverage antibiotics (called empiric therapy). In other words, as soon References as the patient looks sick, start blasting your shotgun at Parrillo JE. Pathogenic mechanisms of septic shock. N Engl J all potential targets. Fire early and hit everything. Med 1993;328:1471-1477. Blood pressure must be supported with fluids and Parrillo JE, moderator. Septic shock in humans: advances in drugs (dopamine and norepinephrine are commonly the understanding of pathogenesis, cardiovascular dys- used) and oxygenation maintained (intubation and me- function, and therapy. Ann Intern Med 1990;113:227-42. chanical ventilation is often required). In the last decades, efforts to block the inflammatory cascade with monoclonal antibodies against endotoxin, Recommended Review Article: tumor necrosis factor, and interleukin-1, anti-inflam- Wheeler, AP, Bernard GR. Treating patients with septic matory agents such as ibuprofen and steroids, and a shock. N Engl J Med 1999;340:207-214.

15 insertions

CHAPTER 3. BACTERIAL SEX GENETICS

The bacterial chromosome is a double-stranded DNA in their cellular capsule. Griffith used smooth encapsu- molecule that is closed in a giant loop. Because there is lated pneumococci, which cause violent infection and only one copy of this molecule per cell, bacteria exist in death in mice, and rough nonencapsulated pneumo- a haploid state. Bacteria do not have nuclear mem- cocci, which do not kill mice. You can think of the en- branes surrounding their DNA. capsulated pneumococci as smooth hit men who kill This chapter does not attempt to cover all the details mice, and the rough nonencapsulated pneumococci as of bacterial genetics, such as replication, transcription, only acting rough (they are pushovers and can't kill a and translation. These topics are covered extensively in flea). Griffith heat-killed the smooth encapsulated bad genetics courses. Instead, this chapter covers the mech- guys and injected them, along with the live rough anisms of bacterial exchange of genetic information. nonencapsulated pushovers, into mice. Lo and behold, You see, procaryotes have it rough as they do not engage the mice died, and when he cultured out bacteria from i n sexual union with other bacteria. They undergo gene the blood, he could only find live smooth encapsulated replication, forming an exact copy of their genome, and pneumococci. The gene encoding the capsule had been then split in two, taking a copy with each half (binary released from the heat-killed bacteria and became in- fission). The cells of higher organisms (eucaryotes) con- corporated into the living rough nonencapsulated bac- tribute a set of gametes from each parent and thus en- teria. The rough bacteria were thus transformed into sure genetic diversity. So how do the sexless creatures virulent encapsulated smooth bacteria. undergo the genetic change so necessary for survival? Scientists now use this method extensively for in- One mechanism is simple mutation. However, it is serting recombinant DNA and for mapping genes on rare for a single point mutation to change an organism chromosomes. It can be used in mapping because the i n a helpful manner. Point mutations usually result in frequency of transformation leading to two traits being nonsense or missense (does this make sense?). There transferred is relative to their distance apart on the are 4 ways in which bacteria are able to exchange ge- genome. The closer they are to each other, the more netic fragments: 1) transformation, 2) transduction, 3) likely that they will be transferred together. conjugation (so much for celibacy), and 4) transposon . TRANSDUCTION CHANGE = SURVIVAL Transduction occurs when a virus that infects bacte- The exchange of genetic material allows for the shar- ria, called a bacteriophage, carries a piece of bacter- i ng of genes that code for proteins, such as those that ial DNA from one bacterium to another. To understand provide antibiotic resistance, exotoxins, enzymes, and this topic, let us digress for a moment and talk about other virulence factors (pili, flagella, and capsules). bacteriophages. Scientists can take advantage of these exchange mechanisms for genetic engineering and chromosomal map- Fig. 3-1. Bacteriophages resemble most viruses in ping. Read on ... but only if you are over 21 years old. having a protein coat called a capsid that surrounds a molecule of DNA or RNA. They look almost like spiders TRANSFORMATION with long skinny necks. The phage will bind by its tail fibers to specific recep- Naked DNA fragments from one bacterium, released tors on the bacterial cell surface. This is called adsorp- during cell lysis, bind to the cell wall of another bac- tion. The phage then undergoes penetration. Much terium. The recipient bacterium must be competent, like a spider squatting down and sinking in its stinger, which means that it has structures on its cell wall that the phage pushes the long hollow tube under its neck can bind the DNA and take it up intracellularly. Recip- sheath through the bacterial cell wall and cytoplasmic i ent competent bacteria are usually of the same species membrane. DNA in the head is injected through the as the donor. The DNA that has been brought in can tube into the bacterium. then incorporate itself into the recipient's genome if there is enough homology between strands (another Fig. 3-2. Following adsorption and penetration, the reason why this transfer can only occur between closely injected DNA takes over the host bacteria's RNA poly- related bacteria). merase for the transcription of phage DNA to mesenger The famous example of this type of exchange is the ex- RNA (mRNA). New capsids, DNA, and enzymes are periment conducted by Frederick Griffith in 1928. He formed, and the bacterial cell fills with new phages. At used the Streptococcus pneumoniae bacteria, which are some point the cell can hold no more particles and lyses, classified into many different types based on differences releasing the phages.

CHAPTER 3. BACTERIAL GENETICS

Figure 3-1

To make things more complicated, there are two types of phages, virulent phages and temperate phages. Virulent phages behave as shown in Fig. 3-2, infecting the bacteria, reproducing, and then lysing and killing the bacteria. On the other hand, temperate phages have a good temperament and do not immediately lyse the bacteria they infect. The temperate phage undergoes adsorption and penetration like the virulent phage but then, rather than undergoing transcription, its DNA becomes incorporated into the bacterial chromosome. The DNA then waits for a command to activate.

Fig. 3-3. The integrated temperate phage genome is called a prophage. Bacteria that have a prophage integrated into their chromosome are called lysogenic because at some time the repressed prophage can become activated. Once activated, the prophage initiates the production of new phages, beginning a cycle that ends with bacterial cell lysis. So temperate phages, although of good temperament, are like little genetic time bombs. Lysogenic immunity is the term used to describe the ability of an integrated bacteriophage (prophage) to Figure 3-2 block a subsequent infection by a similar phage. The first temperate phage to infect a bacteria produces a re- pressor protein. This "survival of the fittest" adaptation terium to another. This process is called transduction. ensures that the first temperate phage is the bacteria's Just as there are two types of phages, there are two sole occupant. types of transduction. Virulent phages are involved in Now that we understand bacteriophages, let's discuss generalized transduction and temperate phages in how these phages can carry bacterial DNA from one bac- specialized transduction.

1 7

CHAPTER 3. BACTERIAL GENETICS

BACTERIAL DNA

DISRUPTED REPLICATED BACTERIAL PHAGE DNA DNA

F 3-3 MISPACKAGED PHAGE DNA BACTERIAL DNA G T

G . A , DNA , , . A DNA . S- DNA . I DNA, . F , DNA - . I - DNA "" . I , PHAGE WITH BACTERIAL DNA . T , . I - F 3-4 , DNA, ( S T S ). T . R - DNA , DNA . I , . (Fig. 3-3). N , Fig. 3-4. Genealied andcion . I , DNA A) A . T DNA , DNA , , . . S , B) D DNA - DNA () . T DNA , , DNA. . T C) C . T DNA . DNA . D) C , Fig. 3-5. Specialied andcion DNA. Escherichia coli. T

18 CHAPTER 3. BACTERIAL GENETICS

Figure 3-5

of the lambda prophage lies between the Escherichia Fig. 3-6. The self-transmissible plasmid (F plasmid) coli gene for biotin synthesis and galactose synthesis. If has a gene that encodes enzymes and proteins that form a splicing error occurs, the biotin (BIO) gene or the the sex penis, that is, sex pilus. galactose (GAL) gene (but not both, as the piece of DNA This long protein structure protrudes from the cell spliced is of a set length) will be carried with the phage surface of the donor F(+) bacterium and binds to and DNA and packaged. Thus the gene for biotin synthesis penetrates the cell membrane of the recipient bacterium can now be transferred to another bacteria that does not (this is finally getting juicy!). Now that a conjugal bridge have that capability. You will frequently hear about this has formed, a nuclease breaks off one strand of the F form of gene acquisition; it is called lysogenic conver- plasmid DNA, and this single strand of DNA passes sion. For example, the gene for Corynebacterium diph- through the sex pilus (conjugal bridge) to the recipient theria's exotoxin is obtained by lysogenic conversion. bacterium. CONJUGATION Conjugation is bacterial sex at its best: hot and heavy! In conjugation DNA is transferred directly by cell-to-cell contact, resulting in an extremely efficient exchange of genetic information. The exchange can occur between unrelated bacteria and is the major mechanism for transfer of antibiotic resistance. For conjugation to occur, one bacterium must have a self-transmissible plasmid, also called an F plasmid (for fertility, not the other word!). Plasmids are circular double-stranded DNA molecules that lie outside the chromosome and can carry many genes, including those for drug resistance. F plasmids encode the enzymes and proteins necessary to carry out the process of conjugation. Bacteria that carry F plasmids are called F(+) cells. In conjugation, an F(+) donor cell will pass its F plasmid to an F( -) recipient cell, thus making the recipient F(+). Figure 3-6

19 CHAPTER 3. BACTERIAL GENETICS

Fig. 3-7. As one DNA strand is passed through the conjugal bridge, the remaining strand is paired with new nucleotide bases (dotted line). The same thing hap- pens to the strand that passes to the other cell. At the end of the sexual union, the conjugal bridge breaks down and both bacteria have double-stranded circular F plasmids. The recipient F(-) cell is now F(+).

Fig. 3-8. Rarely, the extra-chromosomal F plasmid becomes integrated in the neighboring bacterial chromosome much in the same way as a temperate bacteriophage does. The bacterial cell is then called a Hfr cell (High frequency of chromosomal recombinants). This integration can result in two unique mechanisms of DNA transfer:

1) The F plasmid that is now together with the entire bacterial circular DNA undergoes normal conjugation

Figure 3-8

with an F( -) cell. The entire bacterial chromosome (including the integrated F plasmid) will transfer from the Hfr cell to the recipient cell. 2) The integrated F plasmid in the Hfr cell may be excised at a different site from that of integration. This can result in an F plasmid that now also contains a segment of chromosomal DNA. These plasmids are called F' (F prime) plasmids. This F conjugation is analogous to specialized transduction because in both situations a nearby segment of chromosomal DNA is picked up "accidentally" and can be transferred to other bacterial cells. Some plasmids are non-self-transmissible plasmids. These plasmids do not have the genes necessary for di- recting conjugation. They do replicate within their host bacterium, however, and continue to be passed on as the bacteria divide in binary fission. Plasmids are tremendously important medically. Certain plasmids encode enzymes that degrade antibiotics (penicillinase), or generate virulence factors (such Figure 3-7 as fimbriae and exotoxins).

CHAPTER 3. BACTERIAL GENETICS

TRANSPOSONS

Fig. 3.9. T . Y DNA . T DNA iho haing DNA homolog. T - .

T DNA , - , . T - Figure 3-9 DNA . W DNA , DNA . T - , - . GRAM-POSITIVE BACTERIA

CHAPTER 4. STREPTOCOCCI Tests for Strep and Staph Streptoccal Classification

Streptococci and staphylococci are both gram-positive Certain species of streptococci can either completely spheres (cocci) and are responsible for a wide variety of or partially hemolyze red blood cells (RBCs). The strep- clinical diseases. It is often necessary to differentiate tococci are divided into three groups based on their spe- between these two organisms to prescribe the appropri- cific hemolytic ability. The streptococci are incubated ate antibiotic. The first way to differentiate them is to overnight on a blood agar plate. Beta-hemolytic strep- examine their appearance on a Gram stain. Streptococci tococci completely lyse the RBCs, leaving a clear zone of line up one after the other like a strip of button candy, hemolysis around the colony. Alpha-hemolytic strep- while staphylococci appear as a cluster that can be vi- tococci only partially lyse the RBCs, leaving a greenish sualized as a cluster of hospital staff members posing discoloration of the culture medium surrounding the for a group shot (Fig. 4-1). colony. This discolored area contains unlysed RBCs and a green-colored metabolite of hemoglobin. Gamma- Fig. 4-1. A second method to differentiate streptococci hemolytic streptococci are unable to hemolyze the from staphylococci involves the enzyme catalase. A RBCs, and therefore we should really not use the word quick look at our staff (Staph) picture reveals that a "hemolytic" in this situation (the term non-hemolytic CAT has joined them, so the staff picture is CAT(alase) streptococci is often used to avoid confusion). positive. That is, staphylococci possess the enzyme The streptococci can also be classified based on the catalase, whereas streptococci do not. Staphylococci antigenic characteristics of the C carbohydrate (a car- are thus referred to as catalase positive while strepto- bohydrate found on the cell wall). These antigens are cocci are catalase negative. Catalase converts H2O2 called Lancefield antigens and are given letter names (hydrogen peroxide, which is used by macrophages (from A, B, C, D, E, through S). Historically, the and neutrophils) into 1120 and 0 2 . To test for catalase, Lancefield antigens have been used as a major way a wire loop is rubbed across a colony of gram-positive of differentiating the many streptococci. However, cocci and mixed on a slide with 11202. If bubbles appear, there are so many different types of streptococci the enzyme catalase must be present, and so staphylo- that we now rely less on the Lancefield antigens cocci are present. (See Fig. 5-2). and more on a combination of tests such as the above mentioned patterns of hemolysis, antigenic composition (including Lancefield), biochemical reactions, growth characteristics, and genetic studies. Although there are more than 30 species of streptococci, only 5 are significant human pathogens. Three of these pathogens have Lancefield antigens: Lancefeld group A, B and D. The other two pathogenic species of the streptococcal genus do not have Lancefield antigens, and are therefore just called by their species names: One is Streptococcus pneumoniae and the other is actually a big group of streptococci collec- tively called the Viridans group streptococci.

GROUP A BETA-HEMOLYTIC STREPTOCOCCI (also called Streptococcus pyogenes)

These organisms are so-named because they possess the Lancefeld group A antigen and are beta-hemolytic on blood agar. They are also called Streptococcus pyo- Figure 4-1 genes (which means pus-producing) and cause the dis-

22 CHAPTER 4. STREPTOCOCCI

" ," , , 2) S - . 3) S T 4) S : B- A 2 1) C cabohdae: T C delaed anibod mediaed dieae: R L . Streptococcus pyogenes "L G A" 1) R C . 2) G 2) M poein (80 ): T - A . I Local Inaion/Eooin Releae - . H, 1) Sepococcal phangii: T , (B) , - M . T M - , , (), - . I 5 ( . ). B- A - "Mom, m hoa h!!!" : 2) Skin infecion: S ( ), ( 1) Sepolin O: T O , , . T ), ( - - , , , , A - . T . F - ). T A , -- Staphylococcus aureus. T, O (ASO) . O for these infections consists of a penicillinase resistant ASO - penicillin like dicloxacillin, which covers both group A . beta-hemolytic streptococci and Staphylococcus aureus. 2) S S_: T S . "Mom, m hoa h and m kin i diine- T - - gaing!!!!" . Necoiing Faciii ("F- S- 3) Pogenic eooin ( ehogenic "): T A - oin): T - - A , - ( ). C . M , - . S- S - . T T . T - . (H, 1996). M W , , . . . - 4) O epokinae ( . A , , () . L ), halonidae, DNAae, ani-C5a pepi- dae, ( Fig. 2-S). (). Staphylococcus aureus - T - . Y . R - . . G A - G. I B- A 4 - , - local inaion and/o eooin eleae. T : (H, 1996; S, 1988). E 1) S (> 50%).

23 CHAPTER 4. STREPTOCOCCI

Fige 4-3

Fige 4-2 NOT after a skin infection). The 6 major manifestations of rheumatic fever are:

a) Fever. Necrotizing fasciitis can also be caused by Staphylo- b) Myocarditis (heart inflammation). coccus, Clostridium species, gram-negative enterics, or c) Joint swelling (arthritis). mixed infection with more than one of these bacteria d) Chorea (uncontrolled dance-like movements of the ( Stevens, 1992). extremities) which usually begins 2-3 weeks after the 3) Scarlet fever: Certain beta-hemolytic group A pharyngitis. streptococci not only cause a sore throat, but also pro- e) Subcutaneous nodules (rubbery nodules just un- duce an exotoxin called either pyrogenic toxin or ery- der the skin). throgenic toxin. This exotoxin is acquired by lysogenic f) Rash, called erythema marginatum because it conversion (see Chapter 3). The exotoxin produces fever has a red margin that spreads out from its center. (so it is pyrogenic) and causes a scarlet-red rash. The Fig. 4-3. Picture John Travolta in the movie rash begins on the trunk and neck, and then spreads to Rheumatic Fever, the upcoming sequel to Saturday the extremities, sparing the face. The skin may peel off Night Fever. His heart is damaged from the stress of in fine scales during healing. the hours of disco dancing, his joints are aching from "Mom, my body is turning scarlet!!!!" dropping to his knees, and his arms are moving rhyth- mically in a disco choreiform jam. Fig. 4-2. "MOM, help!!!" Pharyngitis, impetigo, and Rheumatic fever is antibody-mediated. There are anti- scarlet fever. Note that scarlet fever actually spares gens in the heart that are similar to the antigens of the the face. beta-hemolytic group A streptococci. Therefore, the antibodies that form to eradicate this particular streptococcus 4) Streptococcal toxic shock syndrome: It is now also cross-react with antigens in the heart. This immuno- clear that beta-hemolytic group A streptococci can cause logic attack on the heart tissue causes heart inflamma- toxic shock syndrome like that caused by Staphylococ- tion, called myocarditis. Patients may complain of chest cus aureus. Similar to scarlet fever, streptococcal toxic shock syndrome is also mediated by the release of pyro- pain and may develop arrhythmias or heart failure. Over years, likely after recurrent infections with genic toxin. See Chapter 5 and Fig. 5-9 for more details. streptococci, the heart becomes permanently damaged. Consider adding clindamycin to penicillin G, as the for- The most frequently damaged site of the heart is the mi- mer rapidly shuts down streptococcal metabolism and tral valve, followed by the aortic valve. These damaged toxin production (Stevens, 1988; Holm, 1996). valves may become apparent many years (10-20) after the initial myocarditis, and can be picked up on physi- Delaed Anibod-Mediaed Dieae cal exam because they produce heart murmurs. So, 1) Rheumatic fever: there is an initial myocarditis, and many years later rheumatic valvular heart disease develops. With the advent of penicillin, rheumatic fever is now These patients are susceptible to recurrent bouts uncommon. It usually strikes children 5-15 years of age. of rheumatic fever and further heart damage. To pre- When it occurs, it has been shown to follow untreated vent further damage to the heart (which is permanent beta-hemolytic group A streptococcal pharyngitis (but and irreversible), prophylactic penicillin therapy is re-

24 CHAPTER 4. STREPTOCOCCI

quired for much of the patient's life. This will prevent future beta-hemolytic group A streptococcal infections, which if they occur will elicit more of the cross-reacting antibodies. Once damaged, the heart valves are susceptible to infection by many other types of bacteria. Therefore, patients with valvular disease need to be given antibiotics whenever they have a dental or surgical procedure. Amoxicillin is commonly given. The joint pain of rheumatic fever is classified as an acute migratory polyarthritis, which is to say that joint pains arise at various sites throughout the day and night. Fortunately, there is no permanent injury to the joints. 2)Acute post-streptococcal glomerulonephritis: This is an antibody-mediated inflammatory disease of the glomeruli of the kidney. It occurs about one week Figure 4-4 after infection of either the pharynx OR skin by nephritogenic (having the ability to cause glomeru- Neonates with meningitis do not present with a stiff neck, which is the classic sign seen in adults. Instead, lonephritis) strains of beta-hemolytic group A strepto- they display nonspecific signs, such as fever, vomiting, cocci. Fortunately, only a few strains of beta-hemolytic group A streptococci are nephritogenic. Certain anti- poor feeding, and irritability. If you even suspect meningitis, you must act rapidly because every minute counts. gens from these nephritogenic streptococci induce an Diagnosis of meningitis is made by a lumbar puncture. antibody response. The resulting antigen-antibody complexes travel to and are deposited in the glomerular Antibiotics are often started prior to the results of the basement membrane, where they activate the comple- lumbar puncture if meningitis is suspected. The organ- Es- ment cascade. This leads to local glomerular destruction isms that must be covered by the antibiotics include cherichia coli, Listeria monocytogenes, and well as group in the kidney. Clinically, a child will show up in your office, and his B streptococcus. These are the 3 most common patho- mother will complain that his face is puffy. This is gens associated with meningitis in infants younger than caused by the retention of fluid from his damaged kid- 3 months of age. ney. His urine is darker than normal (tea or coca-cola colored) due to hematuria (blood in the urine). The child Viridans Group Streptococci may also have hypervolemia secondary to fluid reten- ( No Lancefield antigen classification. Members tion, which can cause high blood pressure. Upon further include Streptococcus salivarius, S. sanguis, S. mitis, questioning you may be able to elicit the fact that he had S. intermedius, S. mutans, and others.) a sore throat or skin infection a week or so ago. This type This is a big, heterogeneous group of streptococci that of glomerular disease usually has a good prognosis (es- are not identified based on one Lancefield group. pecially in the pediatric population). Viridis is the Latin word for green, and most of the "Mom, my urine is tea colored!!!!" viridans streptococci are alpha-hemolytic, producing greenish discoloration on blood agar. They are normal Fig. 4-4. Acute post-streptococcal glomerulonephritis human gastro-intestinal (G.I.) tract flora that are fre- causes tea colored urine (hematuria). quently found in the nasopharynx and gingival crevices. The viridans streptococci cause 3 main types of infec- GROUP B STREPTOCOCCI tion: dental infections, endocarditis, and abscesses. ( also called Streptococcus agalactiae) 1) Dental infections: Some of the viridans streptococci, especially S. mutans, can bind to teeth and fer- These streptococci are also beta-hemolytic. When ment sugar, which produces acid and dental caries thinking of group B streptococci, think of group B for (cavities!!). BABY. About 25% of women carry these bugs vaginally, and 2) Endocarditis: Dental manipulations send show- a baby can acquire these bacteria during delivery. These ers of these organisms into the bloodstream. Subse- organisms cause neonatal (< 3 months of age) meningi- quently, they can implant on the endocardial surface of tis, pneumonia, and sepsis. the heart, most commonly on a previously damaged

25 CHAPTER 4. STREPTOCOCCI

heart valve (such as from old rheumatic fever, a congenital heart defect, or mitral valve prolapse). These bacteria produce an extracellular dextran that allows them to cling to cardiac valves. This results in subacute bacterial endocarditis (SBE), characterized by a slow (hence "subacute") growth and piling up of bacteria on the heart valve (like a pile of bacteria on a petri dish). Clinically, a patient with subacute bacterial endocarditis slowly develops low-grade fevers, fatigue, anemia, and heart murmurs secondary to valve destruction. In contrast, acute infective endocarditis is caused by a staphylococcal infection, often secondary to IV drug abuse, and is characterized by an abrupt onset of shaking chills, high spiking fevers, and rapid valve destruction. Fig. 4-5. When you think of viridans streptococci, think ofVERDE, which is the word for "green" in Span- ish. Now picture the Verde (green) foliage between some incisors-you know, palm trees, vines, the works . When these teeth are pulled by sadistic dentists (they all are), the Verde foliage enters the blood stream and settles on leaflets of the heart valves, especially valves which have been previously damaged (such as valves damaged by rheumatic fever). Fig. 4-6. Viridans Streptococcus is eating heart valves slowly, while Staphylococcus aureus is eating fast (No- tice that these organisms appear as a strip and cluster respectively!). Viridans Streptococcus, slowly eats away at the valve just as a plant slowly grows into soil. This is in sharp contrast to Staphylococcus aureus, who received his Olympic gold (aureus) medals for his ability to rapidly bind to and destroy the heart valves. Therefore, subacute bacterial endocarditis (SBE) is caused by viridans Streptococcus, while acute bacterial endocarditis is the disease associated with Staphylococ- cus aureus. Note that group D streptococci (discussed below) can also cause subacute bacterial endocarditis. Figure 4-5 Interestingly, the streptococci work together as a team to establish SBE. Initially, Streptococcus pyo- should consider investigating with a CAT scan with genes causes rheumatic fever, which damages the heart contrast. valves. Now, viridans Streptococcus or the group D Streptococcus InterMediUS: streptococci can more easily adhere to the heart valves IMmediately USses (asses) for ABSCESS and cause SBE!!! 3) Abscesses: There is a subgroup of the viridans GROUP D STREPTOCOCCI streptococci called the Streptococcus intermedius (Enterococci and Non-enterococci) group (comprised of Streptococcus intermedius, S. con- stellatus, and S. anginosus) which are microaerophilic Traditionally these alpha-hemolytic bacteria have and are part of the normal G.I. tract flora. These oxy- been divided into two subgroups: the enterococci gen hating critters are often found in abscesses in the (comprised of Enterococcus faecalis and Enterococcus brain or abdominal organs. They are found alone in faecium) and the non-enterococci (comprised of many pure cultures or in mixed cultures with anaerobes (like organisms including Streptococcus bovis and Strepto- Bacteroides fragilis). coccus equinus). Recently the enterococci have been A clinical pearl is that if a Streptococcus intermedius shown to be sufficiently different from the streptococci group bacteria grows in the blood you should suspect to be given their own genus enterococcus. S. bovis and that there is an abscess hiding in an organ and you S. equinus are still classified as streptococci.

26 CHAPTER 4. STREPTOCOCCI

Figure 4-6

Enterococcus (faecalis and faecium) ciprofloxacin, chloramphenicol, and doxycycline. A newer class of drugs, the pristinomycins, may also be used: The enterococci take up residence in the human in- dalfopristin (Synercid) + quinupristin (RP 59500). These testines and are considered normal bowel flora. They are cause painful arthralgias in 2% and venous irritation alpha hemolytic and unique in that they all grow well in (less with a central line) in 5%. They are currently 40% bile or 6.5% NaCl. Clinically, the enterococci are available for compassionate use against VRE (Rhone- commonly the infecting agents in urinary tract infec- Poulenc-Rorer, telephone 610-454-3071). To avoid further tions, biliary tract infections (as they grow well in bile), emergence of this resistant strain and worse yet, the bacteremia, and subacute bacterial endocarditis (SBE). transfer of the genes to more virulent bugs like Staphylo- While these bugs are not as virulent as Streptococcus coccus aureus, we must limit the use of vancomycin. For pyogenes, they are always around in the G.I. tract and example, metronidazole must be used for Clostridium dif- prey on weak hospitalized patients. In fact, the entero- Ficile pseudomembranous colitis instead of vancomycin. cocci are close to the second most common cause of nosocomial (hospitally acquired) infections in the U.S. today! Non-Enterocci (Streptococcus bovis and equinus) NEWS FLASH!!!! Read all about it! Enterococcus now resistant to ampicillin and vancomycin! Like the enterococci, Streptococcus bovis is hardy, The enterococci are resistant to most of the drugs we growing in 40% bile (but not in 6.5% NaCl). It lives in use to kill gram positive bacteria. We usually treat ente- the G.I. tract, and it causes similar diseases. rococcal infections with ampicillin plus an aminoglyco- An important unique property is that there is a reside. However, many enterococcal strains are now markable association between S. bovis infection and resistant to both of these agents; in these cases we treat colon cancer!!! In some series 50% of people with S. bo- with vancomycin (see Fig. 16-17). Now our worst night- vis bacteremia have a colonic malignancy. We do not mare has been realized: vancomycin resistant enterococci know if S. bovis is a cause of colon cancer or just a (VRE) have developed and have been spreading in the marker of the disease. U.S. The resistance property is carried on a gene that is BOVIS in the BLOOD: transferable. Enterococci with this resistance gene alter Better Beware, CANCER in the BOWEL their cell wall dipeptide d-alanine-d-alanine (the target for vancomycin, see page 141), changing it to d-alanine- Streptococcus pneumoniae lactate. This change prevents vancomycin binding. (Alias the pneumococcus; No Lancefield antigen) The treatment of multiply resistant enterococci is very difficult and will involve complicated susceptibility test- The pneumococcus is a very important organism being and infectious disease specialty consultation, and will cause it is a major cause of bacterial pneumonia and require us to take some old and some new antibiotics off meningitis in adults, and otitis media in children. pneu- the shelves that are sometimes active against VRE: the mococcus is to parents what group B streptococcus is to glycopeptides (like vancomycin), teicoplanin, rifampin, Babies.

2 7 CHAPTER 4. STREPTOCOCCI

The pneumococcus does not have Lancefield antigens! The first pneumococcal vaccine (the pneumovax) has Under the microscope, they appear as lancet-shaped 25 of the most common capular polysaccharide antigens. gram-positive cocci arranged in pairs (diplococci). It is given to people for whom pneumococcal pneumonia The major virulence factor of the pneumococcus is its would be exceptionally deadly, such as immunocompro- polysaccharide capsule, which protects the organism mised or elderly folk. Individuals without spleens (as- from phagocytosis. Fortunately, the capsule is anti- plenic) or with HIV disease are unable to defend genic, and antibodies specific for the capsule can neu- themselves against encapsulated bacteria and should tralize the pneumococcus. The only problem is that also be vaccinated. Unfortunately, the polysaccharide there are 84 different capsule serotypes, so surviving an vaccine has low immunogenicity and efficacy in chil- infection with this organism only provides immunity to dren. A new heptavalent conjugate vaccine contains 7 1 out of the 83 possible capsule types. (thus heptavalent) capsular polysaccharide antigens There are 2 important lab tests to identify the from serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F conju- pneumococcus: gated with a non-toxic diphtheria-toxin protein, to increase its immunogenicity. This vaccine has almost 1) Quellung reaction: When pneumococci on a slide 100% efficacy in the prevention of invasive pneumococ- smear are mixed with a small amount of antiserum cal infections in children!!! Because serotypes 3, 6B, 9V, (serum with antibodies to the capsular antigens) and 14, 19F, and 23F are the most common causes of otitis methylene blue, the capsule will appear to swell. This tech- media (bold serotypes are covered by vaccine), it also has nique allows for rapid identification of this organism. been shown to reduce cases of otitis media in children Streptococcus pneumoniae 2) Optochin sensitivity. ( Eskola, et. al. N Engl J Med 2001; 344:403-9). is alpha-hemolytic (partial hemolysis-greenish color) but Streptococcus viridans is also alpha-hemolytic! To differentiate the two, a disc impregnated with optochin (you don't want to know the real name) is placed on the agar dish. The growth ofStreptococcus pneumoniae will be inhibited, while Streptococcus viridans will continue to grow. Streptococcus pneumoniae is the most common cause of pneumonia in adults. Pneumococcal pneumonia occurs suddenly, with shaking chills (rigors), high fevers, chest pain with respirations, and shortness of breath. The alveoli of one or more lung lobes fill up with white blood cells (pus), bacteria, and exudate. This is seen on the chest X-ray as a white consolidated lobe. The patient will cough up yellow-green phlegm that on Gram stain reveals gram-positive lancet-shaped diplococci. Fig. 4-7. The "pneumococcal warrior." He is a mighty foe, with "capsule" armor, a lung emblem on his shield, and a lancet-shaped diplococcus lance. The lung emblem on his shield shows the severe lobar pneumonia caused by this organism. Note the consolidation of the middle right lobe and the lower left lobe, which accompany fever and shaking chills. Streptococcus pneumoniae is also the most common cause of otitis media (middle ear infection) in children and the most common cause of bacterial meningitis in adults. The classic sign of meningitis, nuchal rigidity (a stiff neck) is usually present in an adult with meningitis. Fig. 4-8. Otitis media (in children mostly): The pneumococcal warrior's lance zips through the ears of an en- emy soldier!! Fig. 4-9. Meningitis: Our warrior is smashing his en- emy's head with a hammer!! Fige 4-7 CHAPTER 4. STREPTOCOCCI

Fige 4-8 Fige 4-9

Fig. 4-10. We see the doctor shooting a hole through Unfortunately, we are witnessing dramatic changes in our warrior (the pneumococci) with the antibody tipped the way we treat this common and dangerous critter. pneumovax (pneumococcal pneumonia vaccine). Fig. 4-11. Summary of streptococcal groups. NEWS FLASH!!!! Read all about it! Streptococcus pneumoniae now resistant to penicillins! Refeence Certain strains of Streptococcus pneumoniae are now showing intermediate level resistance to penicillin (min- Davies HD, McGreer, A, et al. Invasive group A streptococcal imal inhibitory concentrations (MIC) of 0.1-1.0 micro- infections in Ontario, Canada. N. Eng. J. Med. 1996; 335: grams penicillin per ml blood) and even high level 547-54. resistance ( MIC > 2.0 micrograms/ml blood). In some Eskola J, Kilpi T, et. al. Efficacy of a pneumococcal conjugate vac- European countries 2/3 of strains have intermediate or cine against otitis media. N Engl J Med 2001; 344:403-409. high level resistance! In the U.S. about 10% of strains Holm SE, Invasive group A streptococcal infections. N. Eng. J. Med. 1996; 335: 590-591. have intermediate resistance and 1% high level resis- Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice tance; the percentage is much higher in day care set- of Infectious Diseases; 4th edition. New York: Churchill Liv- tings where children are frequently given antibiotics. ingstone, 1995;1784-1865. Worse yet, the pneumococcus is also acquiring resis- Stevens DL. Invasive group A streptococcus infections. Clinical tance to erythromycin, trimethoprim/sulfamethoxazole, Infectious Diseases 1992; 14:2-13. and chloramphenicol. Stevens DL, Gibbons AE, et al. The eagle effect revisited: effi- The good news is that high dose penicillin (1 million cacy of clindamycin, erythromycin, and penicillin in the treat- units every 4 hours) and the cephalosporins are effec- ment of streptococcal myositis. J. Infect. Dis. 1988;158:23-8. tive against bugs with intermediate level resistance. In Tuomanen EI, Austrian R, Masure HR. Mechanisms of disease: areas where high level resistant strains are common pathogenesis of pneumococcal infection. N Engl J Med vancomycin will have to be added. 1995;332(19 ):1280-1284.

Fige 4-10

29 F 4-11 STREPTOCOCCI M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaster CHAPTER 5. STAPHYLOCOCCI

Staphylococci are forever underfoot, crawling all over cocci and mix on a slide with H2O2. If bubbles appear, hospitals and living in the nasopharynx and skin of up this indicates that H2O2 is being broken down into oxy- to 50% of people. While at times they cause no symp- gen bubbles and water; catalase-positive staphylococci toms, they can become mean and nasty. They will be one are present. of your future enemies, so know them well. The 3 major pathogenic species are Staphylococcus 3) Culture: Staphlococcus aureus and certain aureus, Staphylococcus epidermidis, and Staphylococ- streptococci are beta-hemolytic (completely hemolyze cus saprophyticus. red blood cells on an agar plate), but Staphlococcus au- It is extremely important to know how to differ- reus can be differentiated from the other beta-hemolytic entiate staphylococci from streptococci because most cocci by their elaboration of a golden pigment on sheep staphylococci are penicillin G resistant! You can do 3 blood agar. things to differentiate them-Gram stain, catalase test, and culture. Now that we can differentiate staphylococci from streptococci, it is important to know which species of staphylococcus is the actual pathogen. The key point: Of the 3 pathogenic staphylococcal species, only Staphylo- Fig. 5.1. Staphylococci lie in grape-like clusters as coccus aureus is coagulase positive!!! It elaborates the seen on Gram stain. Visualize this cluster of hospital enzyme, coagulase, which activates prothrombin, caus- staff posing for a group photo. Staphlococcus aureus is ing blood to clot. In Fig. 5-1, note how all the Gold- catalase-positive, thus explaining the cats in the group Medalists (Staphylococcus aureus) hang out together to photo. Staphlococcus aureus (aureus means "gold") show each other their gold medals. You can think of can be differentiated from the other beta-hemolytic them as coagulating together. So when a gram-positive cocci by their elaboration of a golden pigment when cul- coccus in clusters is isolated in culture, the microbiology tured on sheep blood agar. Notice that our hospital laboratory will do a coagulase test. If they report to you Staff (Staph) all proudly wear gold medals around that the test demonstrates coagulase positive grampos- their necks. itive cocci in clusters you know you have Staphylococcus aureus. If they report coagulase negative gram-positive 2) Catalase test: All staphylococci have the enzyme cocci in clusters, think ofStaphylococcus epidermidis or catalase (streptococci do not!). staphylococcus saprophyticus.

Fig. 5-2. Catalase testing, showing a cluster of staphylococci (catalase-positive) blowing oxygen bubbles. To test, rub a wire loop across a colony of gram-positive

Figure 5-1 Figure 5-2

31 CHAPTER 5. STAPHYLOCOCCI

Staphylococcus aureus This critter has a microcapsule surrounding its huge peptidoglycan cell wall, which in turn surrounds a cell membrane containing penicillin binding protein (also called transpeptidase-see page 114). Numerous powerful defensive and offensive protein weapons stick out of the microcapsule or can be excreted from the cytoplasm to wreak havoc on our bodies:

Proteins That Disable Our Immune Defenses 1) Protein A: This protein has sites that bind the Fc portion of IgG. This may protect the organism from opsonization and phagocytosis. 2) Coagulase: This enzyme can lead to fibrin formation around the bacteria, protecting it from phagocytosis. Figure 5-4 3) Hemolysins (4 types): Alpha, beta, gamma, and delta. They destroy red blood cells, neutrophils, macro- Fig. 5-4. Hapless red blood cell following a neutrophil, phages, and platelets. running to destruction at the hands of Staphylococcus 4) Leukocidins: They destroy leukocytes (white aureus and its hemolysis and leukocidin dynamite. blood cells). 5) Penicillinase: This is a secreted form of beta- Proteins to Tunnel Through Tissue lactamase. It disrupts the beta-lactam portion of the 1) Hyaluronidase ("Spreading Factor"): This pro- penicillin molecule, thereby inactivating the antibiotic tein breaks down proteoglycans in connective tissue. (see Chapter 16). 2) Staphylokinase: This protein lyses formed fibrin 6) Novel penicillin binding protein: This protein, clots (like streptokinase). also called transpeptidase, is necssary for cell wall pep- 3) Lipase: This enzyme degrades fats and oils, tidoglycan formation and is inhibited by penicillin. which often accumulate on the surface of our body. This Some strains of Staphylococcus aureus have new peni- degradation facilitates Staphylococcus aureus' coloniza- cillin binding proteins that are resistant to penicilli- tion of sebaceous glands. nase-resistant penicillins and cephalosporins. 4) Protease: destroys tissue proteins. Fig. 5-3. Staphylococcus aureus wielding protein A Fig. 5-5. Staphylococcus aureus produces proteins and coagulase shields, defending itself from attacking that allow the bacteria to tunnel through tissue. antibodies and phagocytosis. Exotoxin Assault Weaponry 1) Exfoliatin: A diffusible exotoxin that causes the skin to slough off (scalded skin syndrome).

Figure 5-3 Figure 5-5

32 CHAPTER 5. STAPHYLOCOCCI

Figure 5-6

2) Enterotoxins (heat stable): Exotoxins which vomiting, diarrhea, abdominal pain, and occasionally cause food poisoning, resulting in vomiting and diarrhea. fever. The episode lasts 12 to 24 hours. 3) Toxic Shock Syndrome toxin (TSST-1): This exotoxin is analogous to the pyrogenic toxin produced by Fig. 5-7. Staphylococcus aureus gastroenteritis. "I Lancefield group A beta-hemolytic streptococci, but is told you not to eat the mayonnaise, sweetheart!" P far more deadly. This exotoxin causes toxic shock 2) Toxic Shock Syndrome: You may have heard syndrome and is found in 20% of Staphylococcus about toxic shock syndrome and super-absorbent tam- aureaus isolates. These pyrogenic toxins are called superantigens and bind to the MHC class II molecules on antigen presenting cells (such as macrophages). The toxin-MHC II complex causes a massive T cell response and outpouring of cytokines, resulting in the toxic shock syndrome described below. (see Fig. 5-9). Fig. 5-6. Staphylococcus aureus produces exotoxin assault weaponry.

Staphylococcus aureus causes a broad range of human disease, and can infect almost any organ system. The diseases can be separated into 2 groups: Disease caused by exotoxin release: 1) Gastroenteritis (food poisoning). 2) Toxic shock syndrome. 3) Scalded skin syndrome. Disease resulting from direct organ invasion by the bacteria: 1) Pneumonia 2) Meningitis 3) Osteomyelitis 4) Acute bacterial endocarditis 5) Septic arthritis 6) Skin infections 7) Bacteremia/sepsis 8) Urinary tract infection Diseases Caused by Exotoxin Release 1) Gastroenteritis: Staphylococci can grow in food and produce an exotoxin. The victim will then eat the food containing the pre-formed toxin, which then stimulates peristalsis of the intestine with ensuing nausea, Figure 5-7

33 CHAPTER 5. STAPHYLOCOCCI

vomiting, and watery diarrhea (enterotoxin-like syndrome), followed in a few days by a diffuse erythematous (red) rash (like scarlet fever). The palms and soles undergo desquamation (fine peeling of the skin) late in the course of the illness. The toxic shock syndrome is also associated with septic shock as described in Chapter 2: blood pressure may bottom out (frank shock) and the patient may suffer severe organ system damage (such as acute respiratory distress syndrome or acute renal failure). Treatment includes cleaning the infected foci, removal of the tampon or drainage of an infected wound, along with supportive care. Antibiotics can help by killing the bacteria and preventing more exotoxin from being produced. However, antibiotics are not curative because it is the exotoxin, not the bacteria, which causes Figure 5-8 the clinical manifestations. 3) Staphylococcal Scalded Skin Syndrome: This pons. It now appears that these tampons, when left in disease is similar in pathogenesis to toxic shock syn- place for a long time, in some way stimulate Staphylo- drome. A Staphylococcus aureus strain, which produces coccus aureus to release the exotoxin TSST-1. This exo- exfoliatin toxin, establishes a localized infection and re- toxin penetrates the vaginal mucosa and is a potent leases a diffusible toxin that exerts distant effects. Un- stimulator of both tumor necrosis factor (TNF) and like toxic shock syndrome, it usually affects neonates interleukin-1 (see page 15). TSST-1 also dramatically with local infection of the recently severed umbilicus or enhances susceptibility to endotoxin. Tampon use is not older children with skin infections. Clinically, it causes the only cause of this syndrome, since men and non- cleavage of the middle epidermis, with fine sheets of menstruating woman can also be affected. skin peeling off to reveal moist red skin beneath. Heal- ing is rapid and mortality low. The doctor must rule out Fig. 5-8. Infected sutures in surgical wounds, cuta- a drug allergy, since this can present similarly and may neous and subcutaneous infections, and infections fol- result in death if the use of the offending drug is not lowing childbirth or abortion can all be foci from which halted. Staphylococcus aureus can release its TSST-1 exotoxin.

Fig. 5-9. Toxic shock syndrome is caused by Staphy- Disease Resulting from Direct lococcus aureus releasing TSST-1. This toxin creates Organ Invasion symptoms that you can think of as a hybrid between food poisoning (enterotoxins) and the streptococcal Fig. 5-10. Diseases caused by direct organ invasion by pyrogenic toxin that produces scarlet fever. The syn- Staphylococcus aureus. Visualize the Staph-wielding drome involves the sudden onset of high fever, nausea, wizard. (Note the cluster of staphylococci at the head of his staff.) The pathology includes:

1) Pneumonia: Staphylococcus aureus is a rare but severe cause of community-acquired bacterial pneumonia. Pneumonia is more common in hospitalized patients. It usually follows a viral influenza (flu) upper respiratory illness, with abrupt onset of fever, chills, and lobar consolidation of the lung, with rapid destruction of the lung parenchyma, resulting in cavitations (holes in the lung). This violent destructive pneumonia frequently causes effusions and empyema (pus in the pleural space). 2) Meningitis, Cerebritis, Brain Abscess: These patients can present with high fever, stiff neck, headache, obtundation, coma, and focal neurologic signs. 3) Osteomyelitis: This is a bone infection that usually occurs in boys under 12 years of age. The infection Figure 5-9 spreads to the bone hematogenously, presenting locally

34 CHAPTER 5. STAPHYLOCOCCI

Figure 5-10 with warm, swollen tissue over the bone and with sys- fection of the joint cavity. Patients complain of an temic fever and shakes. acutely painful red swollen joint with decreased range 4) Acute Endocarditis: This is a violent destruc- of motion. Staphlococcus aureus is the most common tive infection of the heart valves with the sudden onset pathogen causing this disease in the pediatric age of high fever (103-105 F°), chills, and myalgias (like a group and in adults over the age of 50. Without prompt bad flu). The patient with staphylococcal endocarditis treatment, many patients will permanently lose the may have no history of valvular disease and may not function of the involved joint. Diagnosis requires exam- have a murmur. Vegetations grow rapidly on the valve, ination of the synovial fluid, which will characteristi- causing valvular destruction and embolism of vegeta- cally appear yellowish and turbid, with a huge number tions to the brain (left heart valve involvement) or lung of neutrophils (>100,000), as well as a positive Gram (right heart valve infected). Intravenous drug users de- stain or culture. Therapy requires drainage of the joint velop a right-sided tricuspid valve endocarditis and may and antimicrobial therapy. present with pneumonia caused by bacterial emboliza- 6) Skin Infections: Minor skin infections are al- tion from this infected valve. Endocarditis caused by most exclusively caused by either Streptococcus po- Streptococcus viridans and Group D Streptococci has a genes (Group A beta-hemolytic) or b Staphlococcus more gradual onset (see Fig. 4-6). aureus. It is clinically impossible to differentiate the two 5) Septic Arthritis: Invasion of the synovial mem- and, in fact, both may be involved. Streptococci can be brane b Staphlococcus aureus results in a closed in- treated with penicillin G, but staphylococci are often re-

35 CHAPTER 5. STAPHLOCOCCI sistant. Therefore, many doctors believe all skin infec- The Centers for Disease Control reports that MRSA in tions should be treated with a penicillinase-resistant hospital intensive care units has increased from approx- penicillin such as dicloxacillin. imately 20% in 1987 to 60% in 1997 and MRSA strains Skin infections caused by staphylococci or strepto- are now increasingly found in the community. Van- cocci usually follow a major or minor break in the skin, comycin must be used for the treatment of MRSA. Un- with scratching of the site spreading the infection: fortunately, strains of Staphlococcus aureus resistant to Vancomycin are now being reported. Hospital use of a) Impetigo: This contagious infection usually oc- vancomycin must be reserved for only critical indica- curs on the face, especially around the mouth. Small tions to protect this antibiotic from emerging resistance. vesicles lead to pustules, which crust over to become honey-colored, wet, and flaky. b) Cellulitis: This is a deeper infection of the cells. Staphylococcus epidermidis The tissue becomes hot, red, shiny and swollen. Local Abscesses, Furuncles, and Carbuncles: This organism is part of our normal bacterial flora d) and is widely found on the body. Unlike Staphlococcus An abscess is a collection of pus. Infection of a hair fol- licle produces a single pus-filled crater with a red rim. aureus, it is coagulase-negative. This infection can penetrate deep into the subcutaneous This organism normally lives peacefully on our skin These may bore through without causing disease. However, compromised hospi- tissue to become a furuncle. tal patients with Foley urine catheters or intravenous to produce multiple contiguous, painful lesions commu- lines can become infected when this organism migrates nicating under the skin called carbuncles. Significant from the skin along the tubing. abscesses must be surgically drained. Staphlococcus epidermidis is a frequent skin conta- e) Wound infections: Any skin wound can be in- minant of blood cultures. Contamination occurs when fected with Staphlococcus aureus, resulting in an abscess, cellulitis, or both. When a sutured post-surgical the needle used to draw the blood passes through skin Staphlococcus epidermidis. Drawing blood wound becomes infected, it must be reopened and often covered with left open to heal by secondary intention (from the bot- from 2 sites will help determine if growth of Staphlo- coccus epidermidis represents a real bacteremic infec- tom of the wound outward). tion or is merely a contamination. If only one of the 7) Blood and catheter infections: Staphylococ- samples grows Staphlococcus epidermidis, you can cus aureus can migrate from the skin and colonize cen- suspect that this is merely a skin contaminant. How- tral venous catheters resulting in bacteremia, sepsis, ever, if 2 cultures are positive, the likelihood of bac- and septic shock (see page 12), as well as endocarditis. teremia with Staphlococcus epidermidis is high. Staphlococcus epidermidis also causes infections Methicillin-Resistant Staphlococcus of prosthetic devices in the body, such as prosthetic aureus (MRSA) joints, prosthetic heart valves, and peritoneal dialysis catheters. In fact, Staphlococcus epidermidis is the Most staphylococci are penicillin-resistant because most frequent organism isolated from infected in- they secrete penicillinase. Methicillin, Nafcillin, and dwelling prosthetic devices. The organisms have a poly- other penicillinase-resistant penicillins are not broken saccharide capsule that allows adherance to these down by penicillinase, thus enabling them to kill most prosthetic materials. strains of Staphlococcus aureus. MRSA is a strain of Staphlococcus aureus that has acquired multi-drug Staphylococcus saprophyticus resistance, even against methicillin and nafcillin. These strains tend to develop in the hospital, where broad- This organism is a leading cause (second only to E. spectrum antibiotics are used. These antibiotics apply coli) of urinary tract infections in sexually active young a selection pressure that favors multi-drug resistance in women. It is most commonly acquired by females (95%) bacteria (usually acquired by plasmid exchange-see in the community (NOT in the hospital). This organism page 20). is coagulase-negative. MRSA is transferred from patient to patient by the hand contact of health care workers, a strong argument for zealous hand-washing habits!!! This feared bacteria Fig. 5-11. Summary chart of staphylococci. is resistant to almost all antibiotics. Vancomycin is Recommended Review Article: one of the few antibiotics useful in treating infections caused by MRSA, although organisms resistant even to Lowy FD. Medical progress: Staphylococcus aureus infections. vancomycin have been reported in the U.S. and Japan N Engl J Med 1998; 339:520-532. (MMWR 1997; 46: 813-5).

36 Figure 5-11 STAPHYLOCOCCI M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple MedMaster CHAPTER 6. BACILLUS and CLOSTRIDIUM (SPORE-FORMING RODS)

There are 6 medically important gram-positive bacte- infected animal products, such as hides or wool. In the ria: 2 are cocci, and 4 are rods (bacilli). Two of the rods U.S., cases have followed contact with goat hair prod- are spore-formers and 2 are not. We have already dis- ucts from Haiti, such as drums or rugs. Human-to- cussed the 2 gram-positive cocci (streptococci and human transmission has never been reported. staphylococci). In this chapter we will examine the 2 Bacillus anthracis forms a spore which is very stable, gram-positive spore-forming rods, Bacillus and resistant to drying, heat, ultraviolet light, and disinfec- Clostridium. tants, and can survive dormant in the soil for decades. Bacillus and Clostridium cause disease by the release Once it is introduced into the lungs, intestine, or a skin of potent exotoxins (see Fig. 2-8). They differ biochemi- wound, it germinates and makes toxins. The germina- cally by their like or dislike of oxygen. Bacillus enjoys tion and expression of plasmid encoded virulence fac- oxygen (so is aerobic), while Clostridium multiply in tors (on plasmids pXOl and pX02) is regulated by an an anaerobic environment. In an air tight Closet, if increase in temperature to 37°C, carbon dioxide concen- you will! tration, and serum proteins. So the spore actually activates only when introduced into the host! Because of its small size (1-2 µm, ideal for inhalation into alveoli), sta- BACILLUS bility and the nearly 100% lethality of pulmonary an- There are 2 pathogenic species of gram-positive, aer- thrax (after spore inhalation), it is considered an ideal obic, spore-forming rods: Bacillus anthracis and Bacil- candidate for biological terrorism and warfare. It was lus cereus. Bacillus anthracis causes the disease used by the Japanese army in Manchuria in 1940. anthrax while Bacillus cereus causes gastroenteritis (food poisoning). Fig. 6-1. Anthony has Anthrax. This figure demonstrates how the Bacillus anthracis spores are contracted Bacillus anthracis from contaminated products made of hides and goat hair. ( Anthrax) The spores can germinate on skin abrasions (cutaneous anthrax), be inspired into the lungs (respiratory anthrax), Bacillus anthracis is unique in that it is the only bac- or ingested into the gastrointestinal tract (GI anthrax). terium with a capsule composed of protein (poly-D- The spores are often phagocytosed by macrophages in the glutamic acid). This capsule prevents phagocytosis. skin, intestine, or lung and then germinate, becoming Bacillus anthracis causes anthrax, a disease that pri- active (vegetative) gram-positive rods. The bacteria are marily affects herbivores (cows and sheep). Humans are released from the macrophage, reproduce in the lym- exposed to the spores ofBacillus anthracis during direct phatic system, and then invade the bloodstream (up to contact with infected animals or soil, or when handling 10-100 million bugs per milliliter of blood!!!).

Figure 6-1

38 CHAPTER 6. BACILLUS AND CLOSTRIDIUM (SPORE-FORMING RODS)

With a cutaneous anthrax infection (the most com- vaccine composed of the protective antigen (PA). Animals mon route of entry), Bacillus anthracis rapidly multi- are vaccinated with living cultures attenuated by the loss plies and releases a potent exotoxin. This exotoxin of their antiphagocytic protein capsule. These living vac- causes localized tissue necrosis, evidenced by a painless cines are considered too dangerous for human use. round black lesion with a rim of edema. This lesion is called a "malignant pustule" because without antibiotic Bacillus cereus therapy (penicillin), Bacillus anthracis can continue to ("Be serious") proliferate and disseminate through the bloodstream, which can cause death. The skin lesion usually resolves Bacillus cereus is different from Bacillus anthracis in spontaneously in 80-90% of cases, but sometimes that it is motile, non-encapsulated, and resistant to severe skin edema and shock occur. penicillin. Bacillus cereus causes food poisoning (nau- Pulmonary anthrax, called woolsorters disease, is not sea, vomiting, and diarrhea). Food poisoning occurs actually pneumonia. The spores are taken up by when Bacillus cereus deposits its spores in food, which macrophages in the lungs and transported to the hilar and then survive the initial cooking process. The bacteria mediastinal lymph nodes where they germinate. Medi- then germinate in the food and begin releasing their en- astinal hemorrhage occurs resulting in mediastinal terotoxin. To inactivate the spores, the cooked food must widening (enlarged area around and above the heart seen be exposed to high temperatures and/or refrigeration. on chest radiograph and CT scan) and pleural effusions. Bacillus cereus can secrete 2 types of enterotoxins, Gastrointestinal anthrax frequently results in death which cause different kinds of food poisoning: and fortunately is rare. Outbreaks have followed the in- 1) A hea-labile oin similar to the enterotoxin of gestion of spores (often from contaminated meat). Bacil- cholera and the LT from Escherichia coli lus anthracis matures and replicates within the intestine, (ee Fig. 2-8) causes nausea, abdominal pain and diarrhea, lasting where it releases its exotoxin. The exotoxin causes a 12-24 hours. necrotic lesion within the intestine. Patients present with vomiting, abdominal pain, and bloody diarrhea. 2) A hea-able oin produces a clinical syndrome similar to that of Staphlococcus aureus food poisoning, The release of exotoxin is the major reason why an- with a short incubation period followed by severe nausea and vomiting, with limited diarrhea. thrax carries such a high mortality rate. These toxins are encoded on a plasmid called pXOl. The exotoxin When a patient is rushed to the hospital with food contains 3 separate proteins, which by themselves are poisoning, and examination of the food reveals B. nontoxic but together produce the systemic effects of cereus, the best way to respond when your attending or- anthrax: ders you to treat the patient with antibiotics is "Be e- io, Dr. Goofball." Since the food poisoning is caused 1) Edema faco (EF) This is the active A subunit by the pre-formed enterotoxin of Bacillus cereus, antibi- of this exotoxin and is a calmodulin-dependent adeny- otic therapy will not alter the course of this patients late cyclase. It increases cAMP, which impairs neu- symptoms. trophil function and causes massive edema (disrupts water homeostasis). CLOSTRIDIUM 2) Poecie anigen (PA) promotes entry of EF into phagocytic cells (similar to a B subunit of the other Clostridium are also gram-positive spore-forming A-B toxins, see discussion of exotoxins in Chapter 2). rods. However, they are anaeobic, and can therefore 3) Lehal faco (LF) is a zinc metalloprotease that be separated from the aerobic spore-forming rods inactivates protein kinase. This toxin stimulates the (Bacillus) by anaerobic culture. This group of bacteria is macrophage to release tumor necrosis factor a and in- responsible for the famous diseases botulism, tetanus, terleukin-1(3, which contribute to death in anthrax. gas gangrene, and pseudomembranous colitis. A second plasmid, pXO2, encodes three genes neces- Clostridium harm their human hosts by secreting ex- sary for the synthesis of a poly-glutamyl capsule. This tremely powerful exotoxins and enzymes. Rapid diag- capsule inhibits phagocytosis of the vegetative bacteria. nosis of a clostridial infection is crucial, or your patient Both plasmids are critical for bacterial virulence. will die!!!!

Rapid identification and prompt use of penicillin, doxy- Clostridium botulinum cyclin, ciprofloxacin, or levofloxacin are critical in prevent- ( Botulism) ing the high mortality associated with systemic infection by Bacillus anthracis. Individuals taking part in high-risk ac- Clostridium botulinum produces an extremely lethal tivities (petting goats or cows in countries where this dis- neurotoxin that causes a rapidly fatal food poisoning. ease is rampant) and military personnel should be given a The neurotoxin blocks the release of acetylcholine (ACh)

39 CHAPTER 6. BACILLUS AND CLOSTRIDIUM (SPORE-FORMING RODS) from presynaptic nerve terminals in the autonomic ner- Clostridium botulinum matures and synthesizes its vous system and motor endplates, causing flaccid mus- neurotoxin. Those who consume the contents of the jar cle paralysis. when it is opened weeks later ill be ingeing he poen neooin. These afebrile patients initially Adl Bolim develop bilateral cranial nerve palsies causing double vision (diplopia) and difficulty swallowing (dysphagia). Eating smoked fish or home-canned vegetables is as- This is followed by general muscle weakness, which sociated with the transmission of botulism. Clostridium rapidly leads to sudden respiratory paralysis and death. botulinum spores float in the air and can land on food. Patients must immediately be treated with an anti- If the food is cooked thoroughly, the spores will die. toxin, which can neutralize only the unbound free neu- However, if the food with the spores is not cooked suffi- rotoxin in the bloodstream. Intubation and ventilatory ciently, and is then placed into an anaerobic environ- support is critical until the respiratory muscles resume ment (like a glass jar, can, or zip-lock freezer bag), activity.

Figure 6-2

40 CHAPTER 6. BACILLUS AND CLOSTRIDIUM (SPORE-FORMING RODS)

Figure 6-3

Infan Bolim Infant botulism occurs when infants inge food conaminaed ih Clostridium botulinum poe (cases have followed ingestion of fresh honey contaminated with spores). The spores germinate and Clostrid- ium botulinum colonizes the infants intestinal tract. From this location, botulism toxin is released. Initially, the infant will be constipated for two to three days. This is followed by difficulty swallowing and muscle weakness. These "floppy" babies must be hospitalized and given supportive therapy. Prognosis is excellent, so antitoxin is generally not used. Fig. 6-2. Botulism. The adult is eating home-canned beans with neurotoxin while the infant is eating honey Figure 6-4 with spores. The adult often requires intubation and ventilatory support while the baby is merely "floppy." inhibitory neurotransmitters. This inhibiion of in- Clostridium tetani hibitory interneurons allows motor neurons to send a (Tetanus) high frequency of impulses to muscle cells, which results in a sustained tetanic contraction. Clostridium tetani causes tetanus, a disease that classically follows a puncture wound by a rusty nail but Fig. 6-4. Clinically, the patient with tetanus presents can follow skin trauma by any object contaminated with with severe muscle spasms, especially in the muscles of spores. Clostridium tetani spores, which are commonly the jaw (this is called im, or lockjaw). The af- found in soil and animal feces, are deposited in the fected patient exhibits a grotesque grinning expression, wound and can germinate as long as there is a localized called risus adonic, which is due to spasm of the anaerobic environment (necrotic tissue). From this lo- facial muscles. Mortality is high once the stage of lock- cation, Clostridium tetani releases its exotoxin, called jaw has been reached. eanopamin. The tetanus toxin ultimately causes a sustained con- Because of the high mortality of tetanus, prophylactic traction of skeletal muscles called ean. i mmunization with formalin-inactivated toxin (tetanus toxoid) is performed once every ten years in the U. S. Fig. 6-3. Tetany occurs after the tetanus toxin is This booster serves to regenerate the circulating anti- taken up at the neuromuscular junction (end plate) and bodies against tetanus toxin, that were first generated is transported to the central nervous system. There the via childhood immunizations. You may not remember toxin acts on the inhibitory Renshaw cell interneurons, your first shot (you were probably just 2 months old at preventing the release of GABA and glycine, which are the time), but all children in the U. S. are immunized

41 CHAPTER 6. BACILLUS AND CLOSTRIDIUM (SPORE-FORMING RODS)

Fige 6-5 with a series of DPT (diphtheria-pertussis-tetanus) Fig. 6-5. Both botulism and tetanus can lead to res- shots at ages 2, 4, 6, and 18 months, followed by a piratory failure requiring mechanical ventilation. In booster before entry into school (4-6 years). This regi- botulism, there is flaccid muscle paralysis as the acetyl- men provides protection from tetanus (along with diph- choline at the motor end plate is blocked. In tetanus theria and pertussis). However, the protection from there is constant muscle contraction, as the inhibitory tetanus only lasts about 10 years so booster shots of signals are blocked. The tetanic contraction of the res- tetanus are given every 10 years. piratory muscles also results in respiratory failure.

In the emergency room you will encounter 3 types of patients with skin wounds: Clostridium perfringens (Gas Gangrene) 1) Patients who were immunized as a child and received periodic boosters but the last shot was more Everyone has heard of gas gangrene. Prior to anti- than 10 years ago. These patients are given another biotics, Clostridium perfringens devastated soldiers booster. wounded in battle. This bacterium, whose spores can be 2) Patients who have never been immunized. Not found in the soil, matures in anaerobic conditions and only do these patients need a booster, but they should produce gas. The spores can contaminate wounds from also receive preformed antibodies to the tetanus toxin battle or other trauma. Deep wounds with lots of dead called human tetanus immune globulins. tissue create an anaerobic environment that offers an 3) Patients who come to the hospital having already excellent home for Clostridium perfringens. As this developed tetanus. The big picture is to clear the toxin anaerobic organism grows, it releases its battery of and the toxin-producing bacteria and to keep the pa- exotoxin enzymes (see Fig. 2-8), causing further tissue tient alive until the toxin has cleared. This is accom- destruction. plished in the following 5 steps of therapy: Clinically, there are 2 classes of infection with Clos- a) Neutralize circulating toxin with human tridium perfringens: tetanus immune globulins. b) Give an immunization booster to stimulate the 1) Cellulitis/wound infection: Necrotic skin is patient's own immune system to develop anti- exposed to Clostridium perfringens, which grows and tetanus toxin antibodies. damages local tissue. Palpation reveals a moist, spongy, c) Clean the wound, excising any devitalized tis- crackling consistency to the skin due to pockets of gas; sue, to remove any remaining source of Clostridium this is called crepitus. tetani. 2) Clostridial myonecrosis: Clostridium perfrin- d) Antibiotics (penicillin) may help to clear the gens, inoculated with trauma into muscle, secretes exo- remaining toxin-producing bacteria. toxins that destroy adjacent muscle. These anaerobic e) Provide intensive supportive therapy until the bacteria release other enzymes that ferment carbohy- toxin is cleared. Muscle relaxants may have to be drates, resulting in gas formation. A computerized to- administered, and the patient may have to be placed mogram (CT) scan reveals pockets of gas within the on a ventilator. muscles and subcutaneous tissue. As the enzymes de-

42 CHAPTER 6. BACILLUS AND CLOSTRIDIUM (SPORE-FORMING RODS)

grade the muscles, a thin, blackish fluid exudes from Clostridium difficile must be considered as a possible the skin. cause. Samples of the stool can be sent to the laboratory for a Clostridium difficile toxin test. Toxin in the stool Clostridial myonecrosis is fatal unless identified and confirms the diagnosis. treated very early. Hyperbaric oxygen, antibiotics (such Treatment includes discontinuing the initial antibi- as penicillin), and removal of necrotic tissue can be life- otic and administering metronidazole or vancomycin by saving. mouth. Both antibiotics kill Clostridium difficile and are no abobed oall ino he bloodeam. So Clostridium difficile the METRO train and VAN cruise down the gastroin- (Pseudomembranous Enterocolitis) testinal (GI) tract, rather than being absorbed, and run over the hapless Clostridium difficile bacteria (see While you may never see a case of anthrax, tetanus, Chapter 17, Fig. 17-6). or botulism in your career, this will certainly NOT be the case with Clostridium difficile. You will tangle Fig. 6-6. Summary of the Gram-positive spore- with this critter frequently. Clostridium difficile is the forming rods pathogen responsible for antibiotic-associated pseudomembranous colitis (diarrhea), which can follow the use of broad spectrum antibiotics (such as ampicillin, clin- Refeence damycin, and the cephalosporins). These antibiotics can Ciaran PK, et al. Current Concepts: Clostridium difficile Col- wipe out part of the normal intestinal flora, allowing the itis. NEJM 1994;330:257-262. pathogenic Clostridium difficile that is sometimes present to superinfect the colon. Once Clostridium difficile Recommended Reie Aicle: grows in abundance, it then releases its exotoxins. Toxin A causes diarrhea, and Toxin B is cytotoxic to the Dixon TC, Meselson M, et al. Medical Progress: Anthrax. N colonic cells. This disease is characterized by severe di- Engl J Med 1999;341:815-826. arrhea, abdominal cramping, and fever. Hogenauer C, et al. Mechanisms and Management of Antibiotic- Associated Diarrhea. Clinical Infectious Disease 1998;27: Becae of Clostridium difficile i become e 702-710. difficile (difficl) o gie paien anibioic. Pellizzari R, et al. Tetanus and Botulism Neurotoxins: mecha- Examination by colonoscopy can reveal red inflamed nisms of action and therapeutic uses. Philosophical Trans- actions of the Royal Society of London 1999;354:259-268. mucosa and areas of white exudate called pedo- Petit L. Clostridium perfringens: toxinotype and genotype. membane on the surface of the large intestine. Trends in Microbiology March 1999;7:104. Necrosis of the mucosal surface occurs underneath the Shapiro R. Botulism in the United States: A Clinical and Epi- pseudomembranes. demiologic Review. Ann Intern Med 1998;129:221-228. When a patient develops diarrhea while on antibiotics (or within a month of being on antibiotics),

43 Figure 6-6 GRAM-POSITIVE SPORE-FORMING RODS M. Gladwin and 8. Trattler, Clinical Microbiology Made Ridiculously Simple aviedMaster CHAPTER 7. CORYNEBACTERIUM AND LISTERIA (NON-SPORE-FORMING RODS)

We have examined the only 2 gram-positive cocci (Strep- target tissue, so this must be administered quickly to tococcus and Staphylococcus) and the 2 gram-positive prevent damage to the heart and nervous system. spore-producing rods (Bacillus and Clostridium). Now 2) Penicillin or erythromycin: Either antibiotic we will discuss the other 2 gram-positive rods (both non- will kill the bacteria, preventing further exotoxin re- spore-formers): Corynebacterium diphtheriae and Liste- lease and rendering the patient non-contagious. ria monocytogenes. Both of these gram-positive rods 3) DPT vaccine: The child must receive the DPT infect patients in the pediatric age group. vaccine, as infection by Corynebacterium diphtheriae does not always result in immunity to future infection CORYNEBACTERIUM DIPHTHERIAE by this organism. The DPT vaccine stands for: D = Diphtheria; P = Pertussis (Whooping Cough); and Corynebacterium diphtheriae is the pathogen respon- T = Tetanus. The diphtheria portion contains formalin sible for diphtheria. It colonizes the pharynx, forming a i nactivated diphtheria toxin (see Chapter 6, page 41, for grayish pseudomembrane composed of fibrin, leuko- more on DPT). cytes, necrotic epithelial cells, and Corynebacterium diphtheriae cells. From this site, the bacteria release a Now that therapy has been administered, we can sit powerful exotoxin into the bloodstream, which specifi- back, relax, and confirm our clinical suspicion of diph- cally damages heart and neural cells by interfering with theria. On the potassium-tellurite plate, colonies of protein synthesis. Corynebacterium diphtheriae become gray to black within 24 hours. With Loeffler's coagulated blood Fig. 7-1. Visualize the invading Corynebacterium serum, incubation for 12 hours followed by staining diphtheriae organisms as a tiny invading army overrun- with methylene blue will reveal rod-shaped pleomor- ning the throat and building a launching platform on phic bacteria. the pharynx. The army quickly constructs exotoxin rock- Fortunately for nonimmunized children, not all ets. From the safety of their pharynx base, they fire off Corynebacterium diphtheriae secrete this exotoxin. Just deadly rockets to the heart and central nervous system. as Group A beta-hemolytic streptococci must first be lysogenized by a temperate bacteriophage to produce While working in the pediatric emergency room, you the erythrogenic toxin that causes scarlet fever, see a child with a sore throat and fever. There is a dark Corynebacterium diphtheriae first must be lysogenized inflammatory exudate on the child's pharynx, which ap- by a temperate bacteriophage which codes for the diph- pears darker and thicker than that of strep throat. Al- theria exotoxin. though you may feel the urge to scrape off this tightly This powerful exotoxin contains two subunits. The B adherent pseudomembrane, you must resist this temp- subunit binds to target cells and allows the A subunit to tation, because bleeding will occur and the systemic ab- enter the cell. Once inside the cell, the A subunit blocks sorption of the lethal exotoxin will be enhanced. protein synthesis by inactivating elongation factor EF2), which is involved in translation of eucaryotic Being the brightest medical student in the pediatric ( mRNA into proteins (See Fig. 2-S). Notice an interest- emergency room, you immediately recognize that this ing comparison: Anti-ribosomal antibiotics are specifi- child probably has diphtheria. Realizing that you are cally designed to inhibit protein synthesis in bacterial with an extremely powerful exotoxin, you dealing procaryotic) cells. Similarly, this exotoxin specifically "loaf around" (Lo- ( quickly TELL yoUR InTErn not to inhibits protein synthesis in humans (eucaryotes). Thus effler's). Immediately send the throat and nasopharynx this exotoxin can be considered a "human antibiotic," potassium tellurite agar and swabs for culture on because its damage to heart and neural cells can be Loeffler's coagulated blood serum media. However, lethal. these culture results will not be ready for days!!! You may try a Gram stain of a specimen from the pseudomembrane, but gram-positive rods are not always seen. LISTERIA MONOCYTOGENES Since there is no time to loaf with diphtheria, it is often best to proceed rapidly to treatment via the following 3- If your attending or professor ever blurts out the silly step method. statement, "Gram-negative organisms have endotoxin while gram-positive organisms do not," you can proudly 1) Antitoxin: The diphtheria antitoxin only inacti- point out that Listeria monocytogenes, a gram- vates circulating toxin, which has not yet reached its positive motile rod, actually has endotoxin! Al-

45 CHAPTER 7. CORYNEBACTERIUM AND LISTERIA (NON-SPORE FORMING RODS)

though the clinical relevance of this fact is debatable, it is wonderful for that rare moment when you actually impress your attending. If your attending, in retaliation, then attempts to pimp you into submission, describe how Listeria mono. cytogenes exhibits a tropism for nervous tissue, and thus is a common cause of meningitis in 2 particular groups. The first group is neonates, who contract this organism from their asymptomatic mothers during delivery. Lis- teria monocytogenes is the third most common cause of neonatal meningitis, following only group B streptococci and Escherichia coli. The second group of patients at risk for Listeria meningitis is immunosuppressed patients, such as those with cancer, renal transplants, or AIDS. The mortality rate for meningitis in this second group is extremely high. You may wonder why this organism invades neonates and certain immunosuppressed patients but not an immune competent host. The main reason is that Lis- teria monocytogenes is a resistant fellow, able to hide out and survive within certain immune cells, such as macrophages and neutrophils that can phagocytose, or engulf, foreign objects such as bacteria. Since they can survive either outside or within cells, Listeria monocytogenes is called a facultative intracellular organism (see Fig. 2-7). However, in immune competent hosts, the immune system can release factors that activate the macrophage, so that these cells can now destroy the "vagrant" bacteria within them. Immunologists refer to this immune system-mediated method of destroying Listeria as cell-mediated immunity. However, neonates (up to 3 months of age) and immuno suppressed patients are unable to activate their phagocytic cells, thus allowing Listeria monocytogenes to flourish and infect the meninges. Since pregnancy may also de- press cell-mediated immunity, Listeria monocytogenes can infect pregnant women as well, who may develop meningitis or remain asymptomatic carriers. Fig. 7-2. A) The macrophage of a neonate or an immunosuppressed patient. B) The macrophage of an immune competent person. When meningitis develops in a patient who is at high risk for Listeria monocytogenes, it is important to treat it empirically with antibiotics that will cover this bacterium. After a lumbar puncture confirms that this is a bacterial meningitis (cerebrospinal fluid analysis reveals a high number of neutrophils, a high protein level, a low glucose, and the Gram stain of the cerebrospinal fluid may demonstrate gram-positive rods), we must add either ampicillin or trimethoprim-sulfamethoxazole to the antibiotic regimen. These are 2 antibiotics that cover Listeria monocytogenes. Fig. 7-3. Summary of the non-spore-forming gram- Figure 7-1 positive rods.

46 CHAPTER 7. CORYNEBACTERIUM AND LISTERIA (NON-SPORE FORMING RODS)

Figure 7-2

47 'gore 7-i NON SPORE-FORMING GRAM-POSITIVE RODS M Gladwin and B Trattler. Clinical Microbiology Made Ridiculously Simple MedMastei GRAM-NEGATIVE BACTERIA

CHAPTER 8. NEISSERIA

NEISSERIA SEEN UNDER THE MICROSCOPE

I 1 I NEISSERIA MENINGITIDIS NEISSERIA GONORRHOEAE

Figure 8-1

I - Fig. 8-1. M 2 , cocci, Neisseria. T . T . E - . N , , - - , . T , Neisseria . meningitidis, T : Neisseria nervous and irritable (central nervous system ir- meningitidis Neisseria gonorrhoeae. ritation-meningitis). T

49 CHAPTER 8. NEISSERIA

is Neisseria gonorrhoeae, ( U S - -). H " ." I - , - 40%. E " ." H sexually transmitted disease (STD) gonorrhea. , NEISSERIA MENINGITIDIS . F, - , - B , Neisseria meningi- . tidis ( meningococcus) - (). V : Meningococcal Disease 1) Capsule: A Neisseria meningitidis - , () . . R, - Neisseria meningitidis () , , / ( - ( ). ). T "" T 9 ( A, petechial rash. T B, C, D, X, Y, Z, W135, 29E). M A, B, C. , , - 2) Endotoxin (LPS): T , , - . N (G ) () (C 2, 12). T . , , petechiae ( - ). T 1) Meningococcemia: T - . of Neisseria meningitidis - 3) IgA1 protease: T , , ( ), of Neisseria. T IA ( , . T - ) . . O , 4) Neisseria meningitidis - - . . T / . A Neisseria meningitidis 2) Fulminant meningococcemia (Waterhouse- , Friderichsen syndrome): T ( . T - C 2, 12). B ( 5% ) . C- , - , . A - - - , ( ). . D (DIC) H- : . D (6-8 1) Infants aged 6 months to 2 years ). 2) Army recruits 3) Meningitis: T , < 1 D , . I - , , , , , . I / . A , . T, ( , 6 2 ) K B . ( T ). N Haemophilus influenzae - - . . T A - - .

50 CHAPTER 8. NEISSERIA

Diagnosis involves Gram stain and culture of the 2) Protein II: This outer membrane protein is also meningococcus from blood, cerebrospinal fluid, or pe- involved in adherence to host cells. techial scrapings. Neisseria grow best on blood agar that has been heated so that the agar turns brown (called Gonococcal Disease in Men chocolate agar). The classic medium for culturing Neis- A man who has unprotected sex with an infected seria is called the Thayer-Martin VCN media. This is a Neisseria gonorrhoeae infection. chocolate agar with antibiotics, which are included to person can acquire kill competing bacteria. This organism penetrates the mucous membranes of the urethra, causing inflammation of the urethra (urethri- Although some men will remain asymptomatic, V stands for vancomycin, which kills gram-positive tis). organisms. most will complain of painful urination along with a purulent urethral discharge (pus can be expressed from the tip of the penis). Both asymptomatic and sympto- C stands for colistin (polymyxin) which kills all matic men can pass this infection to another sexual gram-negative organisms (except Neisseria). partner. Possible complications of this infection include epi- N stands for nystatin, which eliminates fungi. didymitis, prostatitis, and urethral strictures. Fortu- nately, this disease is easily cured by a small dose of Therefore, only Neisseria (both Neisseria meningi- ceftriaxone. tidis and Neisseria gonorrhoeae) are able to grow on this culture medium. The addition of a high concentration of Gonococcal Disease in Women CO2 further promotes the growth of Neisseria. In the laboratory, the differentiation between the Like men, women can also develop a gonococcal ure- Neisseria species is based on Neisseria meningitidis' thritis, with painful burning on urination and purulent ability to produce acid from maltose metabolism, while discharge from the urethra. However, urethritis in Neisseria gonorrhoeae cannot! women is more likely to be asymptomatic with minimal Prompt treatment with penicillin G or ceftriaxone urethral discharge. is required at the first indication of disseminated Neisseria gonorrhoeae also infects the columnar ep- meningococcemia. Close contacts of an infected patient ithelium of the cervix, which becomes reddened and fri- are treated with rifampin. Immunization with purified able, with a purulent exudate. A large percentage of capsular polysaccharides from certain strains (groups women are asymptomatic. If symptoms do develop, the A, C, Y, and W135) is currently available and used for woman may complain of lower abdominal discomfort, epidemics and in high-risk groups. The group B poly- pain with sexual intercourse (dyspareunia), and a puru- saccharide does not induce immunity, so a vaccine is not lent vaginal discharge. Both asymptomatic and sympto- available at present. matic women can transmit this infection. A gonococcal infection of the cervix can progress to pelvic inflammatory disease (PID, or "pus in dere"). NEISSERIA GONORRHOEAE PID is an infection of the uterus (endometritis), fallopian tubes ( salpingitis), and/or ovaries ( oophori- Neisseria gonorrhoeae, often called the gonococcus, tis). Clinically, patients can present with fever, lower causes the second most commonly transmitted sexual abdominal pain, abnormal menstrual bleeding, and disease, gonorrhea (chlamydial infections are slightly cervical motion tenderness (pain when the cervix is more common). moved by the doctor's examining finger). Menstrua- Virulence factors of the gonococcus include: tion allows the bacteria to spread from the cervix to the upper genital tract. It is therefore not surprising 1) Pili: Neisseria gonorrhoeae has complex genes that over 50% of cases of PID occur within one week coding for their pili. These genes undergo multiple re- of the onset of menstruation. The presence of an in- combinations, resulting in the production of pili with trauterine device (IUD) increases the risk of a cervical hypervariable amino acid sequences. These changing gonococcal infection progressing to PID. Chlamydia antigens in the pili protect the bacteria from our anti- trachomatis is the other major cause of PID (see Chap- bodies, as well as from vaccines aimed at producing an- ter 12, pages 80-82). tibodies directed against the pili. The pili adhere to host cells, allowing the gonococ- Complications of PID include: cus to cause disease. They also serve to prevent phagocytosis, probably by holding the bacteria so close to 1) Sterility: The risk of sterility appears to increase host cells that macrophages or neutrophils are unable with each gonorrhea infection. Sterility is most com- to attack. monly caused by scarring of the fallopian tubes, which

51 CHAPTER 8. NEISSERIA occludes the lumen and prevents sperm from reaching Chlamydia eye infections are also a threa,ythro- the ovulated egg. erythromycin eye drops, which are effective against both Neis- 2) Ectopic pregnancy: The risk of a fetus devel- Nisseria gonorrhoeae and Chlamydia, are given to all oping at a site other than the uterus is significantly newborns. Gonococcal conjunctivitis can also occur in increased with previous fallopian tube inflammation adults. (salpingitis). The fallopian tubes are the most common site for an ectopic pregnancy. Again, with scarring down Diagnosis and Treatment of the fallopian tubes, there is resistance to normal egg transit down the tubes. Diagnosis of Neisseria gonorrhoeae infection is best 3) Abscesses may develop in the fallopian tubes, made by Gram stain and culture on Thayer-Martin ovaries, or peritoneum. VCN medium. Pus can be removed from the urethra by 4) Peritonitis: Bacteria may spread from ovaries inserting a thin sterile swab. When this is Gram stained and fallopian tubes to infect the peritoneal fluid . and examined under the microscope, the tiny doughnut- 5) Peri-hepatitis (Fitz-Hugh-Curtis syndrome): shaped diplococci can be seen within the white blood This is an infection by Neisseria gonorrhoeae of the cap- cells. sule that surrounds the liver. A patient will complain of In the past, the combination of penicillin G with right upper quadrant pain and tenderness. This syn- probenicid was the regimen of choice. However, there drome may also follow chlamydial pelvic inflammatory arose penicillinase-producing gonococcal strains and disease. now an even tougher strain, with chromosomally- mediated antibiotic resistance to many antibiotics, Gonococcal Disease in Both Men such as tetracycline, erythromycin, and trimethoprim) and Women sulfamethoxazole. This resistance is mediated by a block in antibiotic penetration into the bacterial cell. 1) Gonococcal bacteremia: Rarely, Neisseria gon- The current therapy of choice is ceftriaxone, a third orrhoeae can invade the bloodstream. Manifestations generation cephalosporin (see page 131). Ceftriaxone include fever, joint pains, and skin lesions (which usu- will also treat syphilis. If the patient is allergic to ally erupt on the extremities). Pericarditis, endocardi- cephalosporins, spectinomycin or ciprofloxacin can be tis, and meningitis are rare but serious complications of used as an alternative. The patient should also be treated a disseminated infection. at the same time with doxycycline or azithromycin for 2) Septic arthritis: Acute onset of fever occurs Chlamydia trachomatis, because up to 50% of patients along with pain and swelling of 1 or 2 joints. Without will be concurrently infected with this beta-lactam-re- prompt antibiotic therapy, progressive destruction of sistant (ceftriaxone included) bacteria. the joint will occur. Examination of synovial fluid usually reveals increased white blood cells. Gram stain and culture of the synovial fluid confirms the diagnosis, revealing gram-negative diplococci within the white blood BRANHAMELLA CATARRHALIS cells. Gonococcal arthritis is the most common kind of ( Neisseria catarrhalis) septic arthritis in young, sexually active individuals. This organism is part of the normal respiratory flora but can cause otitis media, sinusitis, bronchitis, and Gonococcal Disease in Infants pneumonia (all respiratory tract illnesses). Pneumonia Neisseria gonorrhoeae can be transmitted from a usually occurs in patients with lung disease. These bac- pregnant woman to her child during delivery, resulting teria produce beta-lactamase and are thus resistant to in ophthalmia neonatorum. This eye infection usu- penicillin. ally occurs on the first or second day of life and can damage the cornea, causing blindness. Because neonatal Fig. 8-2. S of Neisseria.

52 Figure 8-2 NEISSERIA M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple MedMaster CHAPTER 9. THE ENTERICS

The enterics are gram-negative bacteria that are part of tart properties of Escherichia coli. Follow this discus- the normal intestinal flora or cause gastrointestinal dis- sion for the overall big picture. ease. The family, genus, and species of all the enterics are You are traveling through Uruguay and wind up in a organized in the chart at the end of this chapter so that village whose people are suffering from a terrible diar- you will not be confused with the different names. Many rhea. After giving intravenous fluids to scores of babies, of these bacteria are referred to simply by their genus you start to wonder whether the cause of this infection name because there are so many different species in some can be eradicated. When questioned, the villagers tell groups. The main groups are Enterobacteriaceae, Vib- you that they obtain their water from a common river. rionaceae, Pseudomonadaceae and Bateroidaceae. You know that the enterics are transmitted by the fecal- These organisms are also divided into groups based oral route, and you begin to wonder if there is fecal con- upon biochemical and antigenic properties. tamination of the river water. How will you prove that the water is fecally contaminated? Escherichia coli to the rescue! You see, Escherichia Biochemical Classification coli is a coliform, which means that it is a normal in- Some of the important biochemical properties of the habitant of the intestinal tract. Think of E. coli = coli- organisms, which can be measured in the lab, are: form = colon. Escherichia coli is normally not found outside the intestine. So if you find Escherichia coli in 1) The ability to ferment lactose and convert it the village stream water, it does not necessarily mean into gas and acid (which can be visualized by including that Escherichia coli is causing the diarrhea, but it does a dye that changes color with changes in pH). Escher tell you that there is fecal matter in the river and that ichia coli and most of the enterobacteriaceae ferment some enteric may be responsible. You pull out your tat- lactose while Salmonella, Shigella and Pseudomonas tered copy of Clinical Micro Made Ridiculously Simple aeruginosa do not. and begin the test. 2) The production ofH2S, ability to hydrolyze urea, 1) Presumptive Test: You add the river water sam- liquefy gelatin, and decarboxylate specific amino acids. ples to test tubes containing nutrient broth (like agar) Some growth media do 2 things at once: 1) They con- that contains lactose. These tubes contain an inverted tain chemicals that inhibit the growth of gram-positive vial that can trap gas and a dye indicator that changes bacteria that may be contaminating the sample. 2) They color if acid is produced. You let the sample grow for a have indicators that change color in the presence of lac- day. If lactose is fermented, gas is produced and the dye tose fermentation. The 2 that you should know are: is visualized. You now know that either Escherichia coli or a nonenteric bacteria that ferments lactose is in the 1) EMB agar (Eosine Methylene Blue): Methylene water. To find out which you continue... blue inhibits gram-positive bacteria, and colonies of lac- 2) Confirmed Test: Streak EMB agar plates with tose fermenters become deep purple to black in this the water samples, and the Escherichia coli should form medium. Escherichia coli colonies take on a metallic colonies with a metallic green sheen. Also Escherichia green sheen in this medium. coli can grow at 45.5C° but most nonenterics cannot, so 2) MacConkey agar: Bile salts in the medium in- you can grow 2 plates at 45.5C° and 37C° and compare hibit gram-positive bacteria, and lactose fermenters de- the colonies on both. velop a pink-purple coloration. 3) Completed Test: Colonies that were metallic green are placed in the broth again. If they produce acid In today's modern laboratories there are plastic trays and gas, then you know the river water contains Es- with up to 30 different media that measure many bio- cherichia coli. chemical reactions, including those just described. A You travel upstream and find an outhouse that has colony of unknown bacteria is inoculated onto each been built in a tree hanging over the water. You inform medium and incubated. A computer then interprets the results and identifies the bacteria. the villagers about the need to defecate in areas that do not have river runoff and teach them to build latrines. Within a few weeks the epidemic has ended! Fecal Contamination of Water Antigenic Classification A classic method for determining whether water has been contaminated with feces demonstrates some of the The enterics form many groups, based on cell surface practical uses of biochemical reactions and some impor- structures that bind specific antibodies (antigenic de-

54 CHAPTER 9. THE ENTERICS

Pathogenesis The organisms in this chapter produce 2 types of disease:

1) Diarrhea with or without systemic invasion. 2) Various other infections including urinary tract infections, pneumonia, bacteremia, and sepsis, especially in debilitated hospitalized patients.

Diarrhea A useful concept in understanding diarrhea produced by these organisms is that there are different clinical manifestations depending on the "depth" of intestinal invasion: 1) No cell invasion: The bacteria bind to the intestinal epithelial cells but do not enter the cell. Diar- rhea is caused by the release of exotoxins (called enterotoxins in the GI tract), which causes electrolyte and fluid loss from intestinal epithelial cells or epithelial cell death. Watery diarrhea without systemic symptoms (such as fever) is the usual picture. Enterotoxi- genic Escherichia coli and Vibrio cholera are examples. 2) Invasion of the intestinal epithelial cells: The bacteria have virulence factors that allow binding and invasion into cells. Toxins are then released that destroy the cells. The cell penetration results in a systemic immune response with local white blood cell infiltration (leukocytes in the stool) as well as fever. The cell death results in red blood cell leakage into the stool. Exam- ples: Enteroinvasive Escherichia coli, Shigella, and Sal- monella enteritidis. Figure 9-1 3) I - : Along with abdominal pain and diarrhea con- terminants). The enterics have 3 major surface anti- taining white and red cells, this deeper invasion results gens, which differ slightly from bug to bug. in of fever, headache, and white blood cell count elevation. The deeper invasion can also 1) 0 antigen: This is the most external component result in mesenteric lymph node enlargement, bactere- of the lipopolysaccharide (LPS) of gram-negative bacte- mia, and sepsis. Examples: Salmonella typhi, Yersinia ria. The 0 antigen differs from organism to organism, enterocolitica, and Campylobacter jejuni. depending on different sugars and different side-chain substitutions. Remember O for Outer (see Fig. 1-6, for Various Other Infections more information on LPS). 2) K antigen: This is a capsule (Kapsule) that covers The enterics are normal intestinal inhabitants and the 0 antigen. usually live with us in peaceful harmony. In the hospi- 3) H antigen: This antigenic determinant makes up tal and nursing homes, however, some bad things hap- the subunits of the bacterial flagella, so only bacteria pen. They acquire antibiotic resistance and can cause that are motile will possess this antigen. Shigella does disease in debilitated patients. They can invade the de- not have an H antigen. Salmonella has H antigens that bilitated patients when Foley catheters are in the ure- change periodically, protecting it from our antibodies. thra or when a patient aspirates vomitus that has been colonized by the enterics. Because of this hospital ac- Fig. 9-1. The 0 antigen forms the outer part of the cell quisition, you will often hear them described as membrane, the K antigen wraps around the cell like a cap- - - or sule, and the arms of the H antigen become wavy flagella. -. Examples: Escherichia coli, Kleb-

55 CHAPTER 9. THE ENTERICS

siella pneumoniae, Proteus mirabilis, Enterobacter, Ser- named after the Aztec chief killed at the hands of the ratia, and Pseudomonas aeruginosa. Spanish explorer, Cortez. The severity of Escherichia coli diarrhea depends on which virulence factors the strain of Escherichia FAMILY ENTEROBACTERIACEAE coli possesses. We will discuss 3 groups of diarrhea- producing Escherichia coli. These have been named Escherichia coli based on their virulence factors and the different diar- Escherichia coli normally resides in the colon without rheal diseases they cause. causing disease. However, there is an amazing amount of DNA being swapped about among the enterics by con- 1) E Escherichia coli (ETEC): jugation with plasmid exchange, lysogenic conversion This Escherichia coli causes travelers diarrhea. It has by temperate bacteriophages, and direct transposon pili (colonization factor) that help it bind to intestinal mediated DNA insertion (see Chapter 3). When Es- epithelial cells, where it releases exotoxins that are sim- cherichia coli acquires virulence in this manner, it can ilar to the cholera exotoxins discussed on page 62. The cause disease: toxins are the (LT), which is just like the cholera toxin, and the (ST). N Escherichia coli ( These exotoxins inhibit the reabsorption of Na and CL - ) + Virulence factors = DISEASE. and stimulate the secretion of Cl and HCO3 - into the intestinal lumen. Water follows the osmotic pull of these V include the following: ions, resulting in water and electrolyte loss. This produces a severe watery diarrhea with up to 20 liters be- 1) Mucosal interaction: ing lost a day!!! T a) Mucosal adherence with pili (colonization ! factor). 2) Enterohemorrhagic Escherichia coli (EHEC): b) Ability to invade intestinal epithelial cells. These Escherichia coli also have a pili colonization 2) Exotoxin production: factor like the ETEC but differ in that they secrete a) Heat-labile and stable toxin (LT and ST). the powerful S- ( also called verotoxin) b) Shiga-like toxin. that has the same mechanism of action as the Shigella 3) Endotoxin: Lipid A portion of lipopolysaccharide toxin (see page 58). They both inhibit protein synthesis ( LPS). by inhibiting the 60S ribosome, which results in 4) Iron-binding siderophore: obtains iron from hu- intestinal epithelial cell death. So these bacteria hold man transferrin or lactoferrin. onto the intestinal epithelial cells and shoot away with the Shiga-like toxin (see F. 9-3). The diarrhea is D caused by Escherichia coli in the presence bloody (hemorrhagic), accompanied by severe abdomi- of virulence factors include the following: nal cramps, and is called . H (HUS) with anemia, 1) Diarrhea. thrombocytopenia (decrease in platelets), and renal fail- 2) Urinary tract infection. ure (thus uremia), is associated with infection by a 3) Neonatal meningitis. strain of EHEC, called Escherichia coli 0157:H7. Nu- 4) Gram-negative sepsis, occurring commonly in de- merous outbreaks have occurred secondary to infected bilitated hospitalized patients. hamburger meat served at fast food chains, suggesting that cattle may be a reservoir for EHEC. Escherichia coli D 3) E Escherichia coli (EIEC): This disease is the same as that caused by Shigella (page 58). Escherichia coli diarrhea may affect infants or adults. In fact, the main virulence factor is encoded in a plas- Infants worldwide are especially susceptible to Es- mid shared by Shigella and Escherichia coli. This plas- cherichia coli diarrhea, since they usually have not yet mid gives the bacteria the ability to actually the developed immunity. Since water lost in the stool is of- epithelial cells. EIEC also produces small amounts of ten not adequately replaced, death from Escherichia Shiga-like toxin. The host tries to get rid of the invading coli diarrhea is usually due to dehydration. About 5 mil- bacteria, and this results in an immune-mediated in- lion children die yearly from this infection. flammatory reaction with . White blood cells in- Adults (and children) from developed countries, trav- vade the intestinal wall, and the diarrhea is bloody with eling to underdeveloped countries, are also susceptible white blood cells. L ! to Escherichia coli diarrhea, since they have not developed immunity during their childhood. This F. 9-2. Vibrio cholera, Escherichia coli, and Shigella is the so-called M dysenteriae all holding hands. Escherichia coli can

56 CHAPTER 9. THE ENTERICS

hospitalized patients. Septic shock (see Chapter 2, page 12) due to the lipid A component of the LPS is usually the cause of death.

Escherichia coli P

Escherichia coli is a common cause of hospital-acquired pneumonia.

Klebsiella pneumoniae

This enteric is encapsulated (0 antigen) but is nonmotile (no H antigen). Klebsiella pneumoniae prowls hospitals, causing sepsis (second most common after Escherichia coli). It also causes urinary tract infections in hospitalized patients with Foley catheters. Hospital- ized patients and alcoholics (debilitated patients) are Figure 9-2 prone to a Klebsiella pneumoniae pneumonia, which is characterized by a bloody sputum in about 50% of cases. This pneumonia is violent and frequently de- cause diarrhea indistinguishable from shigellosis and stroys lung tissue, producing cavities. Thick sputum cholera. The big picture here is that the different types coughed up with Klebsiella pneumoniae classically of diarrhea produced by Escherichia coli and the other looks like red currant jelly, which is the color of the 0 enterics are dependent on virulence acquisition from antigen capsule. The mortality rate is high despite an- plasmids, and there is active sharing of these factors. So tibiotic therapy. Escherichia coli diarrhea can look just like cholera (rice- water stools) or just like shigellosis (diarrhea with blood and white cells). Proteus mirabilis

This organism is very motile. In fact, when you smear Escherichia coli U T the bacteria on a plate it will grow not as distinct round Infections (UTIs) colonies, but rather as a confluence of colonies as the The acquisition of a pili virulence factor allows Es- bacteria rapidly move and cover the plate. This organism is able to break down urea and is thus often referred cherichia coli to travel up the urethra and infect the to as the urea-splitting Proteus. bladder (cystitis) and sometimes move further up to infect the kidney itself (). Escherichia coli There are 3 strains of Proteus that have cross-reacting is the most common cause of urinary tract infections, antigens with some Rickettsia (Chapter 12, F. 12-11). which usually occur in women and hospitalized patients They are OX-19, OX-2, and OX-K. This is purely coinci- with catheters in the urethra. Symptoms include burn- dental but serves as a useful clinical tool to determine ing on urination ( ), having to pee frequently if a person has been infected with Rickettsia. Serum is mixed with these Proteus strains to determine (frequency), and a feeling of fullness over the bladder. Culture of greater than 100,000 colonies of bacteria whether there are antibodies in the serum that react from the urine establishes the diagnosis of a urinary with the Proteus antigens. If these antibodies are present, this suggests that the patient has been infected tract infection. with Rickettsia. Proteus is another common cause of urinary tract in- M Escherichia coli fections and hospital-acquired (nosocomial) infections. Escherichia coli is the second most common cause of Examination of the urine will reveal an alkaline pH, neonatal meningitis (group B streptococcus is first). which is due to Proteus ability to split urea into NH3 During the first month of life, the neonate is especially and CO2. susceptible. Enterobacter Escherichia coli S This highly motile gram-negative rod is part of the Escherichia coli is also the most common cause of normal flora of the intestinal tract. It is occasionally re- gram-negative sepsis. This usually occurs in debilitated sponsible for hospital-acquired infections.

57 CHAPTER 9. THE ENTERICS

Serratia

Serratia is notable for its production of a . It can cause urinary tract infections, wound infections, or pneumonia.

Shigella There are four species of Shigella (dysenteriae, flexneri, boydii, and sonnei) and all are nonmotile. If you look back at the picture of Escherichia coli and Shigella holding hands (F. 9-2), you will see that Shigella has no flagella. Shigella does not ferment lactose and does not produce H2S. These properties can be used to distinguish Shigella from Escherichia coli (lactose fermenter) and Salmonella (non-lactose fermenter, produces H2S). Humans are the only hosts for Shigella, and the dysentery that it causes usually strikes preschool age children and populations in nursing homes. Trans- mission by the fecal-to-oral route occurs via fecally contaminated water and hand-to-hand contact (Em- ployees please wash hands!). Shigella is never considered part of the normal intestinal flora! It is always Figure 9-3 a pathogen. Shigella is similar to enteroinvasive Escherichia coli ( EIEC) in that they both invade intestinal epithelial Salmonella cells and release S , which causes cell de- ("The Salmon") struction. White cells arrive in an inflammatory reaction. The colon, when viewed via colonoscopy, has Salmonella is a non-lactose fermenter, is motile (like shallow ulcers where cells have sloughed off. The illness a salmon), and produces H2S. begins with fever (unlike ETEC and cholera, which do You will hear of Salmonellas Vi . This is a not invade epithelial cells and therefore do not induce polysaccharide capsule that surrounds the O anti- a fever), abdominal pain, and diarrhea. The diarrhea gen, thus protecting the bacteria from antibody attack may contains flecks of bright-red blood and pus (white on the O antigen. This is just like the K antigen (just to cells). Patients develop diarrhea because the inflamed confuse you!), but with Salmonella they named it Vi colon, damaged by the Shiga toxin, is unable to reabsorb (for virulence). fluids and electrolytes. There are thousands of Salmonella serotypes, but clinically they are usually divided into three groups: Salmonella typhi, Salmonella cholerae-suis, and Sal- F. 9-3. Visualize Shazam Shigella with his Shiga monella enteritidis. This will not be that difficult to re- blaster laser, entering the intestinal epithelial cells and member because they are named according to the blasting away at the 60S ribosome, causing epithelial diseases they cause. cell death. Salmonella differs from the other enterics because it lives in the gastrointestinal tracts of and infects humans when there is contamination of food or wa- S T ter with . This is the same toxin as in EHEC and EIEC, and its mechanism is the same. There is an A subunit bound to F. 9-4. Many animals can carry Salmonella. (Pic- 5 B subunits. The B subunits (B for Binding) bind to the ture a salmon.) In the U.S. there was even an epidemic microvillus membrane in the colon, allowing the entry of salmonellosis from pet turtles. Today in the U.S., Sal- of the deadly A subunit (A for Action). The A subunits monella is most commonly acquired from eating chick- inactivate the 60S ribosome, inhibiting protein synthe- ens and uncooked eggs. Salmonella typhi is an sis and killing the intestinal epithelial cell. exception as it is zoonotic (an infectious disease of

58 CHAPTER 9. THE ENTERICS

Figure 9-4

animals that can be transmitted to man). Salmonella ty- exposure and includes fever, headache, and abdominal phi is carried only by humans. pain that is either diffuse or localized to the right lower quadrant (over the terminal ilium), often mimicking ap- Salmonella (like Shigella) is never considered part of pendicitis. As inflammation of the involved organs oc- the normal intestinal flora! It is always pathogenic and curs, the spleen may enlarge and the patient may can cause 4 disease states in humans: 1) the famous ty- develop diarrhea and rose spots on the abdomen-a phoid fever, 2) a carrier state, 3) sepsis, and 4) gas- transient rash consisting of small pink marks seen only troenteritis (diarrhea). on light-skinned people. Typhoid Fever Diagnose this infection by culturing the blood, urine, or stool. Ciprofloxacin or ceftriaxone are considered This illness caused by Salmonella typhi is also called appropriate therapy. enteric fever. Salmonella typhi moves one step beyond EIEC and Shigella. After invading the intestinal epithelial cells, it invades the regional lymph nodes, finally seeding multiple organ systems. During this invasion the bacteria are phagocytosed by monocytes and can survive intracellularly. So Salmonella typhi is a facultative intracellular parasite (see Fig. 2-7). Fig. 9-5. Typhoid fever, caused by Salmonella typhi, depicted by a Salmon with fever (thermometer) and rose spots on its belly. Salmonellosis starts 1-3 weeks after Figure 9-5

59 CHAPTER 9. THE ENTERICS

Carrier State Fig. 9-6. Some people recovering from typhoid fever become chronic carriers, harboring Salmonella typhi in their gallbladders and excreting the bacteria constantly. These people are not actively infected and do not have any symptoms. A famous example occurred in 1868 when Typhoid Mary, a Swiss immigrant who worked as a cook, spread the disease to dozens in New York City. (Again-employees please wash hands after using the toilet!) Some carriers actually require surgical removal of their gallbladders to cure them.

Sepsis Fig. 9-7. Salmon cruising in the bloodstream to infect lungs, brain, or bone. This systemic dissemination is usually caused by Salmonella choleraesuis and does not involve the GI tract. A pearl of wisdom:

Remember that Salmonella is encapsulated with the Vi capsule. Our immune system clears encapsulated bacteria by opsonizing them with antibodies (see Fig 2-5), and then the macrophages and neutrophils in the Figure 9-6 spleen (the reticulo-endothelial system) phagocytose the opsonized bacteria. So, patients who have lost their spleens (asplenic), either from trauma or from sickle-cell Diarrhea (Gastroenteritis) disease, have difficulty clearing encapsulated bacteria and are more susceptible to Salmonella infections. Pa- Fig. 9-8. Salmonella diarrhea is the most common tients with sickle-cell anemia are particularly type of Salmonella infection and can be caused by any prone to Salmonella osteomyelitis (bone infection). of hundreds of serotypes of Salmonella enteritidis. The presentation includes nausea, abdominal pain, and di- Vigorous and prolonged antibiotic therapy is required arrhea that is either watery or, less commonly, contains to treat Salmonella osteomyelitis. mucous and trace blood. Fever occurs in about half the

Figure 9-7

60 CHAPTER 9. THE ENTERICS

Figure 9-S

patients. This diarrhea is caused by a yet-uncharacter- ally an enteric bacterium but is included here because ized cholera-like toxin (watery diarrhea) and sometimes it causes diarrhea. This organism is closely related to also by ileal inflammation (mucous diarrhea). Yersinia pestis, which is the cause of the bubonic plague. Like Yersinia pestis, animals are a major source of Treatment usually involves only fluid and electrolyte Yersinia enterocolitica; Yersinia enterocolitica differs in replacement, as antibiotics do not shorten the course of that it is transferred by the fecal-oral route rather than the disease and do cause prolonged bacterial shedding the bite of a flea. in the stool. The diarrhea only lasts a week or less. Following ingestion of contaminated foods, such as milk from domestic farm animals or fecally contami- Yersinia enterocolitica nated water, patients will develop fever, diarrhea, and abdominal pain. This pain is often most severe in the This motile gram-negative rod is another cause of right lower quadrant of the abdomen, and therefore pa- acute gastroenteritis. Since entero is part of Yersinia tients may appear to have appendicitis. Examination of enterocolitica's name, it is not surprising that this or- the terminal ileum (located in the right lower quadrant) ganism is a cause of acute gastroenteritis. It is not re- will reveal mucosal ulceration.

61 CHAPTER 9. THE ENTERICS

The pathogenesis of this organism is twofold: there is no epithelial cell invasion. The bacteria attach to the epithelial cells and release the cholera toxin, 1) Invasion: Like Salmonella typhi, this organism which is called choleragen. The disease presents with possesses virulence factors that allow binding to the in- the abrupt onset of a watery diarrhea (classically de- testinal wall and systemic invasion into regional lymph scribed as looking like rice water) with the loss of up nodes and the bloodstream. Mesenteric lymph nodes to 1 liter of fluid per hour in severe cases. Shock from swell, and sepsis can develop. isotonic fluid loss will occur if the patient is not rehy- 2) Enterotoxin: This organism can secrete an en- drated. Like ETEC: terotoxin, very similar to the heat-stable enterotoxin of Escherichia coli, that causes diarrhea. Cholera causes death by dehydration. Diagnosis can be made by isolation of this organism Physical findings such as diminished pulses, sunken from feces or blood. Treatment does not appear to alter eyes, and poor skin turgor will develop with severe de- the course of the gastroenteritis, but patients who have hydration. sepsis should be treated with antibiotics. Although refrigeration of food can wipe out many types of bacterial Choleragen pathogens, Yersinia enterocolitica can survive and grow in the cold. This toxin has the same mechanism of action as Es- Other members of the Enterobacteriaceae family that cherichia colis LT toxin (although choleragen is coded you will hear of on the wards include Edwardsiella, Cit- on the chromosome, while LT is transmitted via a plas- robacter, Hafnia, and Providencia. mid). There is one A subunit (Action) attached to five B subunits (Binding). The B subunit binds to the GM1 ganglioside on the intestinal epithelial cell surface, al- FAMILY VIBRIONACEAE lowing entry of the A subunit. In the cell, the A subunit Vibrio cholera activates G-protein, which in turn stimulates the activity of a membrane-bound adenylate cyclase, resulting in the production of cAMP. Intracellular cAMP results in active secretion of Na and Cl as well as the inhibition of Na and Cl reabsorption. Fluid, bicarbonate, and potassium are lost with the osmotic pull of the NaCl as it travels down the intestine. Microscopic exam of the stool should not reveal leukocytes (white cells) but may reveal numerous curved rods with fast darting movements. Treatment with fluid and electrolytes is lifesaving, and doxycycline will shorten the duration of the illness.

Vibrio parahaemolyticus Figure 9-9 This organism is a marine bacterium that causes gastroenteritis after ingestion of uncooked seafood (sushi). Fig. 9-9. As you can see, Vibrio cholera is a curved gram-negative rod with a single polar flagellum. This organism is the leading cause of diarrhea in Japan.

Cholera is the diarrheal disease caused by Vibrio Campylobacter jejuni cholera. The bacteria are transmitted by the fecal-oral route, and fecally contaminated water is usually the (Camping bacteria in the jejunum with nothing bet- culprit. Adults in the U.S., especially travelers, and ter to do than cause diarrhea!) children in endemic areas are the groups primarily infected (immunity develops in adults in endemic areas). This critter is important!!! This gram-negative rod Recent epidemics have arisen secondary to poor dis- that looks like Vibrio cholera (curved with a single po- posal of sewage in many South American countries lar flagellum) is often lost deep in textbooks. Dont let (400,000 cases in Latin America in 1991), and 1993 this happen. Campylobacter jejuni, ETEC, and the Ro- monsoon floods that mixed feces with potable water in tavirus are the three most common causes of diarrhea Bangladesh. in the world. Estimates are that Campylobacter jejuni The bacteria multiply in the intestine and cause the causes up to 2 million cases of diarrhea a year in the same disease as ETEC, but more severe. As with ETEC, U.S. alone.

62 CHAPTER 9. THE ENTERICS

This is a zoonotic disease, like most Salmonella (except 2) The rascal is resistant to almost every antibiotic, Salmonella typhi), with reservoirs of Campylobacter je- so it has become an art to think up "anti-pseudomonal juni in wild and domestic animals and in poultry. The fe- coverage." Drug salesmen will always mention the cov- caloral route via contaminated water is often the mode erage for Pseudomonas. of transmission. This organism can also be acquired by drinking unpasteurized milk. As with most diarrheal ill- Pseudomonas aeruginosa is an obligate aerobic (non- ness, children are the most commonly affected worldwide. lactose fermenter), gram-negative rod. It produces a The illness begins with a prodrome of fever and green fluorescent pigment (fluorescein) and a blue pig- headache, followed after half a day by abdominal cramps ment (pyocyanin), which gives colonies and infected and a bloody, loose diarrhea. This organism invades the wound dressings a greenish-blue coloration. It also pro- lining of the small intestine and spreads systemically as duces a sweet grape-like scent, so wound dressings and do Salmonella typhi and Yersinia enterocolitica. Campy- agar plates are often sniffed for organism identification. lobacterjejuni also secretes an LT toxin similar to that Pseudomonas aeruginosa has weak invasive ability. of Escherichia coli and an unknown cytotoxin that de- Healthy people just don't get infections with this guy! stroys mucosal cells. However, once inside a weakened patient, the story changes. It elaborates numerous exotoxins including Helicobacter pylori exotoxin A, which has the same mechanism of action (formerly called Campylobacter pylori) as diphtheria toxin (stops protein synthesis) but is not antigenically identical. Some strains also possess a cap- This organism is the most common cause of duo- sule that is antiphagocytic and aids in adhesion to tar- denal ulcers and chronic gastritis (inflamed stomach). get cells (in the lungs for example). (Aspirin products rank second.) It is the second leading cause of gastric (stomach) ulcers, behind aspirin products. The evidence for this is as follows: Important Pseudomonas aeruginosa Infections 1) Helicobacter pylori can be cultured from ulcer craters. 1) Pneumonia (see Fig. 16-5) 2) Feeding human volunteers Helicobacter pylori a) Most cystic fibrosis patients have their lungs causes ulcer formation and gastritis. colonized with Pseudomonas aeruginosa. These pa- 3) Pepto-Bismol, used for years for gastritis, has bis- tients develop a chronic pneumonia, which progres- muth salts, which inhibit the growth of Helicobacter pylori. sively destroys their lungs. 4) Antibiotics help treat duodenal and gastric ulcer b) Immunocompromised patients (cancer pa- disease: Multiple recent studies have shown that treat- tients and intensive care unit patients) are highly ment with combinations of bismuth salts, Metronida- susceptible to pneumonia caused by Pseudomonas zole, ampicillin, and/or tetracycline, clears Helicobacter aeruginosa. pylori and results in a dramatic decrease in both duo- 2) Osteomyelitis denal and gastric ulcer recurrence (Veldhuyzen van a) Diabetic patients have an increased risk of de- Zanten, 1994; Ransohoff, 1994; Sung, 1995). veloping foot ulcers infected with Pseudomonas aeruginosa. The infection can penetrate into the Fig. 9-10. Helicobacter pylori causes duodenal and bone resulting in osteomyelitis. gastric ulcers and gastritis. Visualize a Helicopter- b) Intravenous (IV) drug abusers have an in- bacteria lifting the cap off a duodenal and gastric ulcer creased risk of osteomyelitis of the vertebrae or crater. If you have a more violent disposition, visualize clavicle. an Apache helicopter-bacteria shooting hellfire mis- c) Children develop osteomyelitis secondary to siles at the stomach. puncture wounds to the foot. 3) Burn-wound infections: This organism sets up FAMILY PSEUDOMONADACEAE significant infections of burn wounds, which eventually lead to a fatal sepsis. Pseudomonas aeruginosa 4) Sepsis: Pseudomonas sepsis carries an extremely You are going to hear so much about this bug while high mortality rate. working in the hospital that you will wish the Lord had 5) Urinary tract infections, pyelonephritis: This never conjured it up. There are two reasons why it is so occurs in debilitated patients in nursing homes and in important: hospitals. They often have urethral Foley catheters, which serve as a source of infection. 1) It colonizes and infects sick, immunocompromised 6) Endocarditis: Staphylococcus aureus and Pseudo- hospitalized patients, the kind of patient you will take monas aeruginosa are frequent causes of right heart care of in the hospital. valve endocarditis in IV drug abusers.

63 CHAPTER 9. THE ENTERICS

Figure 9-10

7) Malignant external otitis: A Pseudomonas ex- FAMILY BACTEROIDACEAE ternal ear canal infection burrows into the mastoid bone, primarily in elderly diabetic patients. We have spent so much time studying all the preced- 8) Corneal infections: This can occur in contact ing enteric bacteria that you may be surprised to find lens wearers. out that 99% of the flora of our intestinal tract is made up of obligate anaerobic gram-negative rods comprising Treatment ofPseudomonas is complicated as it is re- the family Bacteroidaceae. The mouth and vagina are sistant to many antibiotics. Chapter 16, Fig. 16-14, lists also home to these critters. all the antibiotics used to treat Pseudomonas. An antipseudomonal penicillin is usually combined with an aminoglycoside for synergy (for example, piperacillin Bacteroides fragilis and gentamicin). This bacterium is notable for being one of the few Pseudomonas cepacia is rapidly becoming an im- gram-negative bacteria that does not contain lipid A in portant pathogen, infecting hospitalized patients (burn its outer cell membrane (NO endotoxin!). However, it and cystic fibrosis patients) in a similar manner. does possess a capsule.

64 CHAPTER 9. THE ENTERICS

You will become very familiar with Bacteroides frag- Fusobacterium ilis while studying surgery. This bacterium has low virulence and normally lives in peace in the intestine. This bacterium is just like Bacteroides melaninogeni- However, when a bullet tears into the intestine, when a cus in that it also causes periodontal disease and aspi- seat belt lacerates the intestine in a car wreck, when ab- ration pneumonias. Fusobacterium can also cause dominal surgery is performed with bowel penetration, abdominal and pelvic abscesses and otitis media. or when the intestine ruptures secondary to infection (appendicitis) or ischemia, THEN the bacteria go wild in ANAEROBIC GRAM-POSITIVE COCCI the peritoneal cavity, forming abscesses. An abscess is Peptostreptococcus (strip or chain of cocci) and Pepto- a contained collection of bacteria, white cells, and dead coccus (cluster of cocci) are gram-positive anaerobes tissue. Fever and sometimes systemic spread accom- that are part of the normal flora of the mouth, vagina, pany the infection. and intestine. They are mixed with the preceding or- 'Phis abscess formation is also seen in obstetric and ganisms in abscesses and aspiration pneumonias. gynecologic patients. Abscesses may arise in a patient Members of the Streptococcus viridans group, dis- with a septic abortion, pelvic inflammatory disease cussed in Chapter 4, are mentioned here because they (tubo-ovarian abscess), or an intrauterine device (IUD) are gram-positive, microaerophilic, and are frequently for birth control. isolated from abscesses (usually mixed with other anaer- Bacteroides fragilis is rarely present in the mouth, so obic bacteria). These oxygen-hating critters have many it is rarely involved in aspiration pneumonias. names (such as Streptococcus anginosus and Streptococ- Following abdominal surgery, antibiotics that cover cus milleri) and are a part of the normal GI flora. anaerobes are given as prophylaxis against Bacteroides fragilis. These include clindamycin, metronidazole Fig. 9-11. Summary of enteric bacteria. (Flagyl), chloramphenicol, and others (see Chapter 16, Fig. 16-15). If an abscess forms, it must be surgically References drained. Veldhuyzen van Zanten SF, Sherman PM. Helicobacter pylori infection as a cause of gastritis, duodenal ulcer, gastric cancer and nonulcer dyspepsia: a systematic overview. Can Bacteroides melaninogenicus Med Assoc F 1994;150:177-185. This organism produces a black pigment when grown Veldhuyzen van Zanten SF, Sherman PM. Indications for on blood agar. Hence, the name melaninogenicus. It treatment of Helicobacter pylori infection: a systematic overview. Can Med Assoc F 1994;150:189-198. lives in the mouth, vagina, and intestine, and is usually Ransohoff DF. Commentary. ACP Journal Club 1994; 120: involved in necrotizing anaerobic pneumonias caused 62-63. by aspiration of lots of sputum from the mouth (during Sung, JY, et al. Antibacterial treatment of gastric ulcers asso- a seizure or drunken state). It also causes periodontal ciated with Helicobacter pylori. New Engl J Med 1995;332: disease. 139-42.

Microbiology Made Ridiculously Simple ©MedMaster Figure 9-11 (continued) M. Gladwin and B. Trattler, Clinical CHAPTER 10. HAEMOPHILUS, BORDETELLA, LEGIONELLA

The gram-negative rods Haemophilus influenae, Borde- Haemophilus influenzae type b tella pertussis and Legionella pneumophila are grouped together because they are all acquired through the respi- 1) Meningitis: This is the most serious infection ratory tract. This makes sense if you consider the species caused by encapsulated Haemophilus influenae type b. names: influenae (the flu-an upper respiratory ill- Prior to the introduction of vaccination of U.S. children ness),pertussis (cough), and pneumophila (lung loving). in 1991, it was the main cause of meningitis in young children between the age of 6 months to 3 years (more Haemophilus influenzae than 10,000 cases per year). Following inhalation, this organism invades the local lymph nodes and blood- The name Haemophilus influenae describes some of stream, and then penetrates into the meninges. Since its properties: infants usually do not display the classic stiff neck, non- Haemophilus means "blood loving." This organism specific signs such as fever, vomiting, and altered men- requires a blood-containing medium for growth. Hema- tal status are the clues to this potentially fatal infection. tin found in blood is necessary for the bacteriums cy- Although mortality with appropriate antibiotics is tochrome system. Blood also contains NAD, needed for less than 5%, up to half of infected children will still metabolic activity. have permanent residual neurologic deficits, such as influenzae: This bacterium often attacks the lungs mental retardation, seizures, language delay, or deaf- of persons debilitated by a viral influenza infection. ness. When a bacterial meningitis is treated with an- During the 1890 and 1918 influenza pandemics, scien- tibiotics, the killed bacteria lyse and release cellular tists cultured Haemophilus influenae from the upper antigens, such as LPS lipid A (endotoxin), resulting in a respiratory tracts of "flu" patients, leading them to in- violent immune response that destroys neurons as well correctly conclude that Haemophilus influenae was the as bacteria. Recent studies show that treatment with etiologic agent of the flu. steroids 15-20 minutes before giving N antibiotics will Haemophilus influenae is an obligate human para- decrease this risk of developing neurologic deficits. It is site that is transmitted via the respiratory route. Two theorized that the steroids limit the inflammatory re- important concepts help us understand how this critter causes disease: sponse to the dead bacterias antigens while allowing bacterial killing. 1) A polysaccharide capsule confers virulence: There 2) Acute epiglottitis: Haemophilus influenae type are 6 types of capsules, designated a, b, c, d, e, and f. Of b can also cause rapid swelling of the epiglottis, ob- these, type b is commonly associated with invasive structing the respiratory tract and esophagus. Follow- Haemophilus influenae disease in children, such as ing a sore throat and fever, the child develops severe meningitis, epiglottitis, and septic arthritis. upper airway wheezing (stridor) and is unable to swallow. Excessive saliva will drool out of the childs mouth Capsule b = bad as it is unable to pass the swollen epiglottis. The large, Nonencapsulated strains of Haemophilus influenae red epiglottis looks like a red cherry at the base of the can colonize the upper respiratory tract of children and tongue. If you suspect this infection, do not examine the adults. They lack the virulent invasiveness of their en- larynx unless you are ready to insert an endotracheal capsulated cousins and can only cause local infection. breathing tube because manipulation can cause laryn- They frequently cause otitis media in children as well as geal spasm. This may cause complete airway obstruc- respiratory disease in adults weakened by preexisting tion that can only be bypassed with a tracheotomy. lung disease, such as chronic bronchitis from smoking 3) Septic arthritis: Haemophilus influenae type b or recent viral influenza infection. is the most common cause of septic arthritis in infants. 2) Antibodies to the capsule are lacking in infants Most commonly, a single joint is infected, resulting in and children between 6 months and 3 years of age. The fever, pain, swelling and decreased mobility of the joint. mother possesses antibodies against the b capsule Examination of the synovial fluid (joint fluid) by Gram which she has acquired in her lifetime. She passes these stain reveals the pleomorphic gram-negative rods. antibodies to the fetus transplacentally and in her 4) Sepsis: Children between 6 months to 3 years pre- breast milk. These "passively" acquired antibodies last sent with fever, lethargy, loss of appetite, and no evi- for about 6 months. It takes 3-5 years of Haemophilus dence of localized disease (otitis media, meningitis, or influenzae' colonization and infection for children to de- epiglottitis). Presumably the bacteria invade the blood- velop their own antibodies. So there is a window during stream via the upper respiratory tract. Since the spleen which children are sitting ducks for the invasive is the most important organ in fighting off infection by Haemophilus influenzae. encapsulated bacteria, it is not surprising that children

68 CHAPTER 10. HAEMOPHILUS, BORDETELLA, AND LEGIONELLA

with absent or non-functioning spleens (either by 2) Herpes (Herpes simplex virus 1 and 2): Herpetic surgery or with sickle-cell disease) are at highest risk. lesions start as vesicles (blisters), yet once they break Prompt identification and treatment will prevent they can be misdiagnosed as chancroid, especially be- Haemophilus influenzae type b from invading the cause they are painful. Herpes is usually accompanied meninges, epiglottis, or a joint. by systemic symptoms such as myalgias and fevers. Meningitis, epiglottitis, and bacterial sepsis are Chancroid does not usually produce systemic symptoms. rapidly fatal without antibiotic therapy. Ampicillin 3) Lymphogranuloma venereum (Chlamydia tra- used to be the drug of choice prior to the development of chomatis): LGV has painless matted suppurative in- resistance. Ampicillin resistance is transmitted by a guinal lymph nodes that develop much more slowly plasmid from strain to strain of Haemophilus influen- than chancroid. The primary ulcer of LGV disappears zae. Currently, a third generation cephalosporin, such before the nodes enlarge, whereas with chancroid they as cefotaxime or ceftriaxone, is the drug of choice for coexist. serious infections. Ampicillin or amoxicillin can be used for less serious infections, such as otitis media. Treat chancroid with erythromycin or trimethoprim/sulfamethoxazole. Effective treatment of genital ulcers is crucial, because these open lesions create a Vaccination break in the skin barrier, increasing the risk of HIV (Hib capsule vaccine) transmission. The key to controlling this organism is to stimulate Gardnerella vaginalis the early generation of protective antibodies in young children. However, it is difficult to stimulate antibody (formerly Haemophilus vaginalis) formation in the very young. This organism causes bacterial vaginitis in conjunc- The first vaccine, consisting of purified type b cap- tion with anaerobic vaginal bacteria. Women with sule, was effective only in generating antibodies in chil- vaginitis develop burning or pruritis (itching) of the dren older than 18 months. A second new vaccine is labia, burning on urination (dysuria), and a copious, composed of the Haemophilus influenzae type b (Hib) foul-smelling vaginal discharge that has a fishy odor. It capsule and diphtheria toxin. The addition of the diph- can be differentiated from other causes of vaginitis theria toxin activates T-lymphocytes and antibodies (such as Candida or Trichomonas) by examining a slide against the b capsule. Vaccination with the Hib capsule of the vaginal discharge (collected from the vagina dur- of children in the U.S. at ages 2, 4, 6, and 15 months ing speculum exam) for the presence of clue cells. Clue (along with the DTP and polio vaccines) has dramati- cells are vaginal epithelial cells that contain tiny pleo- cally reduced the incidence of Haemophilus influenzae morphic bacilli within the cytoplasm. infection. Acute Haemophilus influenzae epiglottitis is Treat this infection with metronidazole, which cov- now rarely seen in U.S. emergency rooms. ers Gardnerella as well as co-infecting anaerobes. As a note, this species was separated from the genus Hib, Hib, Hurray! Haemophilus because it does not require X-factor or V- Other efforts involve immunizing women in the factor for growth in culture. eighth month of pregnancy, resulting in increased antibody secretion in breast milk (passive immunization). Bordetella pertussis This bacterium is named: Haemophilus ducreyi Bordetella because it was discovered in the early 1900's by two scientists named Bordet and Gengou. It This species is responsible for the sexually transmitted seems that Bordet got the better end of the deal! disease chancroid. Clinically, patients present with a Pertussis means "violent cough." Bordetella pertus- painful genital ulcer. Unilateral painful swollen in- sis causes whooping cough. guinal lymph nodes rapidly develop in half of infected persons. The lymph nodes become matted and will rup- Exotoxin Weapons ture, releasing pus. The differential diagnosis includes: Bordetella pertussis is a violently militant critter with a (gram) negative attitude. He is a gram-negative 1) Syphilis ( Treponema pallidum): It is extremely rod armed to the hilt with 4 major weapons (virulence important to exclude syphilis as the cause of the ulcer. factors). These virulence factors allow him to attach to Remember that the ulcer of syphilis is painless and the the ciliated epithelial cells of the trachea and bronchi. associated adenopathy is bilateral, painless, and non- He evades the host's defenses and destroys the ciliated suppurative (no pus). cells, causing whooping cough.

69 CHAPTER 10. HAEMOPHILUS, BORDETELLA, AND LEGIONELLA

1) Pertussis toxin: Like many bacterial exotoxins hands or in an aerosolized form. A week-long incubation this toxin has a B subunit that Binds to target cell re- period is followed by 3 stages of the disease: ceptors, "unlocks" the cell, allowing entry of the A subunit. The A subunit (A for Action) activates 1) Catarrhal stage: This stage lasts from 1-2 weeks cell-membrane-bound G regulatory proteins, which in and is similar to an upper respiratory tract infection, with turn activate adenylate cyclase. This results in an out- low-grade fevers, runny nose, sneezing, and mild cough. pouring of cAMP, which activates protein kinase and It is during this period that the disease is most contagious. other intracellular messengers. The exact role of this 2) Paroxysmal stage: The fever subsides and the toxin in whooping cough is not entirely clear, but it has infected individual develops characteristic bursts of 3 observed effects: a) histamine sensitization, b) in- nonproductive cough. There may be 15-25 of these at- crease in insulin synthesis, and c) promotion of lympho- tacks per day, and the person may appear normal be- cyte production and inhibition of phagocytosis. tween events. The attacks consist of 5-20 forceful coughs followed by an inspiratory gasp through the nar- 2) Extra cytoplasmic adenylate cyclase: When attacking the bronchi, Bordetella pertussis throws its rowed glottis. This inspiration sounds like a whoop. adenylate cyclase grenades. They are swallowed by host During these paroxysms of coughing the patient can be- neutrophils, lymphocytes, and monocytes. The internal- come hypoxemic and cyanotic (blue from low oxygen), ized adenylate cyclase then synthesizes the messenger the tongue may protrude, eyes bulge, and neck veins en- cAMP, resulting in impaired chemotaxis and impaired gorge. Vomiting often follows an attack. The paroxys- generation of H2O2 and superoxide. This weakens the mal stage can last a month or longer. The illness is more host defense cells' ability to phagocytose and clear the severe in the young, with up to 75% of infants less than bacteria. 6 months of age and 40% of infants and young children 3) Filamentous hemagglutinin (FHA): Bordetella more than 6 months requiring hospitalization. pertussis does not actually invade the body. It attaches Infants and partially immunized (wearing off) chil- to ciliated epithelial cells of the bronchi and then re- dren and adults may not have the typical whoop. In- leases its damaging exotoxins. The FHA, a pili rod ex- fants can have cough and apnea spells (no breathing). tending from its surface, is involved in this binding. Adults may present with a persistent cough. Antibodies directed against the FHA prevent binding Examination of the white blood cells will surprisingly and disease, and thus they are protective. reveal an increase in the lymphocyte count with just a 4) Tracheal cytotoxin: This toxin destroys the cili- modest increase in the neutrophils (more like a viral pic- ated epithelial cells, resulting in impaired clearance of ture). The increased number of lymphocytes seems to be bacteria, mucus, and inflammatory exudate. This toxin one of the manifestations of the pertussis toxin. is probably responsible for the violent cough. 3) Convalescent stage: The attacks become less frequent over a month, and the patient is no longer contagious. Whooping Cough Since this organism will The number of cases of whooping cough has decreased not grow on cotton, speci- dramatically since vaccination programs began. In the mens for culture are collected from the posterior pharynx with a prevaccination era in the United States, there were ap- calcium alginate swab. This swab is i proximately 100-300 thousand cases a year, and now nserted into the posterior nares and the patient is then only 1-4 thousand!!! Prior to the development of the vac- instructed to cough. The swab is then wiped on a special cine, children between the ages of culture medium with potato, blood, and glycerol agar, 1-5 were most likely called the to catch this disease. Bordet-Gengou medium. At most hospi- The majority of cases today occur in unimmunized in- tals, identification of this bacterium can be made with fants younger than 1 year. Infants younger than 6 rapid serological tests (ELISA). months used to be protected by maternal antibodies Treatment is primarily supportive. Infants are hospi- that crossed the placenta during pregnancy. However, talized to provide oxygen, suctioning of respiratory secre- the vaccine only provides a high level of protective anti- tions, respiratory isolation, and observation. Treatment of infected individuals with bodies during the first 15 years of life, so most mothers erythromycin in the pro- do not have protective antibodies to pass to their in- dromal or catarrhal stage may prevent the disease. Later fants. Therefore, unimmunized infants under 1 year are therapy during the paroxysmal stage does not alter the very susceptible to this infection today. Since the vac- course of illness but may decrease bacterial shedding. Household contacts should receive erythromycin also. cine only provides immunity for approximately 15 years, young adults are another group that is currently Vaccination at a higher risk for acquiring whooping cough. Whooping cough is a highly contagious disease with The vaccine currently used in the U.S. consists of transmission occurring via respiratory secretions on the heat-killed organisms and includes the pertussis toxin,

70 CHAPTER 10. HAEMOPHILUS, BORDETELLA, AND LEGIONELLA

FHA, and adenylate cyclase. It is combined with the for- tiac fever to a severe pneumonia called Legionnaires' malin inactivated tetanus and diphtheria toxoids to disease: form the DPT (Diphtheria-Pertussis-Tetanus) vaccine, Like influenza, this disease in- and is given at 2, 4, 6, and 15-18 months of age. This 1) Pontiac fever: vaccine has been very effective in reducing the number volves headache, muscle aches, and fatigue, followed by fever and chills. Pontiac fever strikes suddenly and of whooping cough cases but carries a price. Infants may develop side effects such as local swelling and pain and completely resolves in less than one week. Pontiac fever was so-named for the illness that struck 95% of systemic fever, persistent crying, and, rarely, limpness the employees of the Pontiac, Michigan, County (hypotonicity) and seizures. In efforts to reduce these adverse effects new vaccines Health Department. The causative agent was identi- have been developed that are composed only of inacti- fied as Legionella pneumophila carried by the air con- vated proteins such as pertussis toxin, FHA, and others ditioning system. Legionnaires' disease: Patients develop very (such as pertactin and fimbrial antigens). In two recent 2) large studies, these vaccines were found to be safer and high fevers and a severe pneumonia. Legionella pneumophila is one of the most common worked better than the U.S. whole-cell vaccine!!! (Greco, 1996; Gustafsson, 1996). causes of community acquired pneumonia and is estimated to be diagnosed correctly in only 3% of cases! It should be suspected in all patients who have pneumonia who are over 50 years of age and especially if they Legionella pneumophila are smokers or if the sputum gram stain reveals neu- (Legionnaires' Pneumonia) trophils and very few organisms. (Legionella is so small Legionella pneumophila is an aerobic gram-negative it is hard to see on gram stain.) rod that is famous for causing an outbreak of pneumo- Treat with erythromycin because this organism has nia at an American Legion convention in Philadelphia a beta-lactamase making it resistant to penicillins. in 1976 (thus its name). Then attempt to determine the source of Legionella. Is This organism is ubiquitous in natural and man- the air conditioning system contaminated? made water environments. Aerosolized contaminated water is inhaled, resulting in infection. Sources that Fig. 10-1. S Haemophilus, Bordetella have been identified during outbreaks have included air Legionella. conditioning systems, cooling towers, and whirlpools. Outbreaks have even been associated with organism References growth in shower heads and produce mist machines in supermarkets!!! Person-to-person transmission has not Greco D, Salmaso S, et al. A controlled trial of two acellular been demonstrated. vaccines and one whole-cell vaccine against pertussis. N. Like Mycobacterium tuberculosis, this organism is a Eng. J. Med. 1996;334:341-8. facultative intracellular parasite that settles in the Gustafsson L, Hollander H0, et al. A controlled trial of a two- lower respiratory tract and is gobbled up by macro- component acellular, a five-component acellular, and a whole-cell pertussis vaccine. N. Eng. J. Med. 1996;334:349- phages. This means that once it has been phagocytosed, 55. it inhibits phagosome-lysosome fusion, surviving and Hewlett EL. Bordetella species. In: Mandell GL, Bennett JE, replicating intracellularly. Dolin R. Editors. Principles and Practice of Infectious Dis- Legionella is responsible for diseases ranging from eases. 4th edition. New York: Churchill Livingstone asymptomatic infection and a flulike illness called Pon- 1995;2078-2084.

71 F 10-1 HAEMOPHILUS, BORDETELLA AND LEGIONELLA M. Gladwin and B. Trattler, Clinical Microbiolog Made Ridiculousl Simple ©MedMaster CHAPTER 11. YERSINIA, FRANCISELLA, BRUCELLA, AND PASTEURELLA

T - 2) V and W antigens: T , (Pas- , teurella 2): Yersinia . T . 1) T - (). Fig. 11-1. V F I 2) A (.., - (F), VW , . T ). Yersinia pestis 3) T . . T , , . T . 4) F ( ) - . T - facultative intracellular organisms. T - , , , , , . L ( F. 2-7) -, -- (DTH) . T () - 1-2 . T - Figure 11-1 Fig. 11-2. Yersinia pestis - - ( DTH - . T C 14, 104) - - 5) T . T Yersinia pestis: - ( ) / , , , . T . . W Yersinia pestis ( ), (B P) . A , Y bubonic plague . . R PESTS (Yersinia pestis) , D ( ), , Yersinia pestis . B , E- . T 14 . L . C I ( 10 ) T 1900 S F. T . T - - U. S. , (boubon G T Fl, V, W - ""). T (- , , . F . T ): , , , . H 1) Fraction 1 (Fl): T - , . "B D." W ,

73 CHAPTER 11. YERSINIA, FRANCISELLA, BRUCELLA, AND PASTEURELLA

Figure 11-2 few days. During epidemics, the disease can also be seen ing rabbits, other mammals, and even reptiles and fish. as pneumonic plague with pneumonia and human-to- Tularemia is distributed all over the U.S. human transmission by aerosolized bacteria. If you see a patient who has been camping in Arizona Fig. 11-3. Francis (Francisella) the rabbit (rabbit or New Mexico and has developed fever, have a high in- vector) is playing in the Tulips (Tularensis). One ear dex of suspicion. You may want to start gentamicin has a tick, the other a deerfly. right away. You can't depend on the presence of swollen lymph nodes: Between 1980 and 1984, 25% of the cases Like Yersinia pestis, this organism is extremely viru- in New Mexico did not have lymph node involvement. lent and can invade any area of contact, resulting in This disease is deadly if untreated! About 75% of un- more than one disease presentation. The most impor- treated people die! tant diseases caused by Francisella tularensis are the Control of epidemics involves DDT for the fleas and ulceroglandular and pneumonic diseases: destruction of the rats. If you only kill the rats, the starving fleas will feed on humans instead! 1) Ulceroglandular tularemia: Following the bite Another species of Yersinia called Yersinia enterocol- of a tick or deerfly, or contact with a wild rabbit, a well- itica infects the colon and is closely related to Es- demarcated hole in the skin with a black base develops. cherichia coli (see Chapter 9 page 61). Fever and systemic symptoms develop, and the local lymph nodes become swollen, red, and painful (some- Francisella tularensis times draining pus). The bacteria can then spread to the (Tularemia) blood and other organs. Note that these symptoms are almost identical to bubonic plague, but the skin ulcer is Tularemia is a disease that resembles bubonic plague usually absent in the plague and the mortality rate is so closely that it is always included in the differential di- not nearly as high as in bubonic plague, reaching 5% for agnosis when considering bubonic plague. This disease ulceroglandular tularemia. is most commonly acquired from handling infected rab- 2) Pneumonic tularemia: Aerosolization of bacte- bits and from the bites of ticks and deerflies. More ria during skinning and evisceration of an infected than a hundred creatures carry this bacterium, includ- rabbit or hematogenous spread from the skin (ulcerog-

CHAPTER 11. YERSINIA, FRANCISELLA, BRUCELLA, AND PASTEURELLA

Figure 11-3 landular tularemia) to the lungs can lead to a lung in- Humans acquire Brucella from direct contact with fection (pneumonia). infected animal meat or aborted placentas, or ingestion of infected milk products. The incidence of this dis- Francisella tularensis can also invade other areas of ease worldwide is greater than that of both bubonic contact such as the eyes (oculoglandular tularemia) plague and tularemia. In the U. S., however, it is not and the gastrointestinal tract (typhoidal tularemia). very common because cattle are immunized and milk is Because this bacterium is so virulent (just 10 organ- pasteurized. isms can cause disease), most labs will not culture it Fig. 11-4. If you do see a patient with brucellosis, he from blood or pus. For the same reason it is not advis- will most likely be a worker in the meat-packing indus- able to drain the infected lymph nodes. Diagnosis rests on the clinical picture, a skin test similar to the PPD for tuberculosis, and the measurement of the titers of antibodies to Francisella tularensis.

Brucella (Brucellosis) All the names of Brucella species are based on the animal they infect: Brucella melitensis (goats) Brucella abortus (causes abortions in cows) Brucella suis (pigs) Brucella canis (dogs) Figure 11-4

75 CHAPTER 11. YERSINIA, FRANCISELLA, BRUCELLA, AND PASTEURELLA

try (beef), a veterinarian, a farmer, or a traveler who consumes dairy (cow or goat) products in Mexico or else- where.

Like the other bacteria in this chapter, Brucella penetrates the skin, conjunctiva, lungs, or GI tract. How- ever, neither buboes nor a primary skin ulcer appear. Penetration is followed by lymphatic spread, facultative intracellular growth in macrophages, and blood and organ invasion. The symptoms are systemic with fever, chills, sweats, loss of appetite, backache, headache, and sometimes lymphadenopathy. The fever usually peaks in the evening and slowly returns to normal by morning. The slow rise in temperature during the day, declining at night, has led to its other name, undulant fever. These symptoms can last from months to years, but for- Figure 11-5 tunately the disease is rarely fatal. Diagnosis of active disease is best made by culture of the organism from the blood, bone marrow, liver, or lymph nodes. Serologic examination that demonstrates This bacterium causes the most frequent wound in- elevated anti-Brucella antibodies suggests active dis- fection following a cat or dog bite. When a patient comes ease. A skin test (with brucellergin) similar to that for in with a cat or dog bite (or scratch), it is important not tularemia is available, but a positive result only indi- to close the wound with sutures. A closed wound creates cates exposure to the organism and does not prove that a pleasant environment for Pasteurella multocida there is active brucellosis. growth, and the resulting infection can invade local joints and bones. Treat infected patients with penicillin Pasteurella multocida or doxycycline. This organism is a gram-negative zoonotic organism. Fig. 11-6. Summary of zoonotic gram-negative rods. However, it is NOT a facultative intracellular organism!!!! This bacterium colonizes the mouths of cats Recommended Review Articles: much in the same way that Streptococcus viridans colonizes the human nasopharynx. It also causes disease in Gill V, Cunha B. Tularemia Pneumonia; Seminars in Respi- other mammals and birds. ratory Infections, Vol 12, No. 1; 1997; 61-67. Titball R, Leary S. Plague. British Medical Bulletin 1998;54: Fig. 11-5. Cat chasing a bird in a"Pasteur." 625-633.

76 Figure 11-6 ZOONOTIC GRAM-NEGATIVE RODS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaster CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Chlamydia and Rickettsia are 2 groups of gram-negative both RNA and DNA (while viruses have either DNA or bacteria that are obligate intracellular parasites. This RNA). Also, unlike viruses they both synthesize their means they can survive only by establishing "residence" own proteins and are sensitive to antibiotics. inside animal cells. They need their host's ATP as an energy source for their own cellular activity. They are Fig. 12-1. Comparison of Chlamydia and Rickettsia energy parasites, using a cell membrane transport with bacteria and viruses. system that steals an ATP from the host cell and spits out an ADP. Both Chlamydia and Rickettsia have this Chlamydia and Rickettsia cause many distinct hu- ATP/ADP translocator. They differ in that Rickettsia man diseases. Chlamydia spreads by person-to-person can oxidize certain molecules and create ATP (via ox- contact, while Rickettsia spreads by an arthropod vector. idative phosphorylation) while Chlamydia does not appear to have this cytochrome system and in fact has no mechanism for ATP production. The obligate intracellu- CHLAMYDIA lar existence brings up 2 questions: Chlamydia is extremely tiny. It is classified as gram- Q: How do we grow and isolate these creatures when negative because it stains red with Gram stain tech- nonliving media do not contain ATP??? nique and has an inner and outer membrane. Unlike A: Indeed, the obligate intracellular existence makes other gram-negative bacteria, it does not have a pepti- it impossible to culture these organisms on nonliving ar- doglycan layer and has no muramic acid. tificial media. However, we can inoculate Chlamydia or Rickettsia into living cells (most commonly chick em- Fig. 12-2. Chlamydia wearing his CLAM necklace bryo yolk sac or cell culture). next to a herpes virus demonstrating that Chlamydia Q: Are these bacteria really viruses, since they is about the same size as some of the large viruses. are very tiny and use the host's cell for their own reproduction???? Chlamydia is especially fond of columnar epithelial A: Although Chlamydia and Rickettsia share a few cells that line mucous membranes. This correlates well characteristics with viruses (such as their small size with the types of infection that Chlamydia causes, in- and being obligate intracellular parasites), they have cluding conjunctivitis, cervicitis, and pneumonia.

Bacteria Chlamydiae Viruses and rickettsiae Size(nm.) 300-3000 350 15-350 Obligatory No YES YES intracellular parasites Nucleic acids RNA DNA RNA DNA RNA Q8 DNA Reproduction Fission Complex Synthesis and cycle with assembly fission Antibiotic YES YES NO sensitivity Ribosomes YES YES NO Metabolic YES YES NO enzymes Energy YES NO NO production Figure 12-1 COMPARISON OF CHLAMYDIA AND RICKETTSIA WITH BACTERIA AND VIRUSES

78 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

ing the initial body (IB). Although the IB synthesizes its own DNA, RNA, and proteins, it requires ATP from the host. Therefore, Chlamydia is considered an energy parasite as well as an intracellular parasite.

Fig. 12-4. The Chlamydia life cycle:

A) The infectious particle is the elementary body (EB). The EB attaches to and enters (via endocytosis) columnar epithelial cells that line mucous membranes. B) Once within an endosome, the EB inhibits phagosome-lysosome fusion and is not destroyed. It transforms into an initial body (IB). C) Once enough IBs have formed, some transform back Figure 12-2 into EB. D) The life cycle is completed when the host cell liber- The Chlamydia life cycle is complex as the bacteria ates the elementary body (EB), which can now infect exist in 2 forms: more cells. 1) Elementary body (EB): This is a metabolically inert (does not divide), dense, round, small (300 nm.), in- There are 3 species of Chlamydia. Chlamydia tra- fectious particle. The outer membrane has extensive chomatis primarily infect the eyes, genitals, and lungs; disulfide bond cross-linkages that confer stability for ex- Chlamydia psittaci and Chlamydia pneumonia only tracellular existence. infect the lungs. All are treated with tetracycline or erythromycin. Fig. 12-3. Think of the elementary body as an elementary weapon like the cannon ball, fired from host Fig. 12-5. Chlamydial diseases. cell to host cell, spreading the infection. Chlamydia trachomatis 2) Initial body (also called reticulate body): Once inside a host cell the elementary body inhibits phago- Fig. 12-6. Chlamydia trachomatis primarily infects some-lysosome fusion, and grows in size to 1000 nm. Its the eyes and genitals. Picture a flower child with RNA content increases, and binary fission occurs, form- groovy clam eyeglasses and a clam bikini.

Figure 12-3

79 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Figure 12-4

Specie Dieae Chlamydia trachomatis eope A, B, C Tachoma (a leading cae of blindne in he old) 1. Inclion conjnciii (all in nebon, conaced in he bih eope D h K canal) 2. Infan pnemonia 3. Ceicii 4. Nongonococcal ehii in men eope L, L2, L3 Lmphoganloma eneem (LGV) Chlamydia psittaci Apical pnemonia Chlamydia pneumoniae .Apical pnemonia Seogop TWAR Figure 12-5 CHLAMYDIAL DISEASES

Trachoma hand transfer of infected eye secretions and by sharing contaminated clothing or towels. Blindness develops Chlamydia trachomatis is responsible for trachoma, slowly over 10-15 years. a type of chronic conjunctivitis that is currently the leading cause of preventable blindness in the world. Fig. 12-7. The conjunctival infection causes inflam- It is a disease of poverty, prevalent in underdeveloped mation and scarring. Scar traction (trachtion for trach- parts of the world. In the U. S., Native Americans are oma) pulls and folds the eyelid inward so that the the group most frequently infected. Children act as the eyelashes rub against the conjunctiva and cornea, main reservoir, and transmission occurs by hand-to- which causes corneal scarring, secondary bacterial in-

80 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Figure 12-6

fections, and ultimately blindness. Simple treatment with topical tetracycline prevents this illness.

Inclusion Conjunctivitis

As Chlamydia trachomatis is the most common sexually transmitted disease in the U. S., it is not surprising that many babies delivered through birth canals in- Figure 12-7 fected with this organism develop inclusion conjunctivitis. Conjunctival inflammation with a purulent antibodies and/or demonstration of Chlamydia tra- yellow discharge and swelling of the eyelids usually chomatis in clinical specimens. Treat with oral ery- arises 5-14 days after birth. In the U. S., all newborns thromycin. are given erythromycin eye drops prophylactically. Diagnosis is made by demonstrating basophilic in- Urethritis tracytoplasmic inclusion bodies in cells taken from scrapings of the palpebral conjunctival surface. These Urethritis, an infection of the urethra, is usually con- inclusion bodies are collections of initial bodies in the cy- tracted sexually. Neisseria gonorrhoeae is the most fa- toplasm of the conjunctival cells. mous bacterium causing urethritis, but not the most common. Urethritis that is not caused byNeisseria gon- Infant Pneumonia orrhoeae is called nongonococcal urethritis (NGU), and is thought to be the most common sexually transmit- A babys passage through an infected birth canal may ted disease. NGU is predominantly caused by Chlamy- also lead to a chlamydial pneumonia, which usually oc- dia trachomatis and Ureaplasma urealyticum. curs between 4-11 weeks of life. Initially, the infant de- Many patients with NGU are asymptomatic. Symp- velops upper respiratory symptoms followed by rapid tomatic patients develop painful urination (dysuria) breathing, cough, and respiratory distress. along with a thin to thick, mucoid discharge from the Diagnosis is made clinically, and the diagnosis can be urethra. It is impossible clinically to differentiate gono- later confirmed by the presence of anti-chlamydial IgM coccal urethritis from NGU and they often occur to-

81 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

gether as a mixed infection. These mixed infections are chronic pelvic pain. It is estimated that 1 million women discovered when patients are treated only with a peni- suffer from PID every year in the U.S. and 25% of them cillin family antibiotic and dont get better. Penicillins will become infertile. In one prospective study (We- treat the gonorrhea, but are ineffective against Chlamy- strom, 1992), tubal occlusion leading to infertility oc- dia trachomatis. Remember that Chlamydia trachoma- curred in 8% of women after 1 episode of PID, 19.5% tis has no peptidoglycan layer, which is the target for after 2 episodes, and 40% after 3 episodes. Likewise, the penicillin. risk of ectopic pregnancy and chronic pelvic pain in- Therefore, all patients diagnosed with urethritis are creases with recurrent PID. empirically treated with antibiotics to cover Neisseria Chlamydia trachomatis is particularly dangerous as gonorrhoeae, Chlamydia trachomatis, and Ureaplasma it often causes asymptomatic or mild PID that goes un- urealyticum. A commonly used treatment regimen in- diagnosed and untreated, yet can still lead to infertility. volves a single dose of intramuscular ceftriaxone (a third-generation cephalosporin that is extremely effec- Fig. 12-8. Infected fallopian tubes scar easily, which tive against Neisseria gonorrhoeae) followed by a 7-day can result in infertility. The silent sinister CLAM course of oral doxycycline or 1 oral dose of azithromycin (Chlamydia trachomatis) causes asymptomatic PID (which covers both Chlamydia trachomatis and Urea- that can lead to infertility. plasma urealyticum). (See Chapter 17, page 131.) While the patient is on empiric antibiotics, diagnostic A simple shot of ceftriaxone and 14 days of oral tests are performed to determine which organism is re- doxycycline will vanquish PID. sponsible. The diagnosis of chlamydial NGU is a bit roundabout because the bacteria are too small to visu- (McCormack, 1994) alize with the Gram stain and cannot be cultured on nonliving media. If the Gram stain reveals polymor- Epididymitis phonuclear leukocytes but NO intracellular or extracellular gram-negative diplococci (that is, NO Neisseria Chlamydial epididymitis can develop in men with gonorrhoeae ), a diagnosis of NGU is likely. If cultures urethritis and presents clinically as unilateral scrotal fail to grow the Neisseria gonorrhoeae, then a diagnosis swelling, tenderness, and pain, associated with fever. of NGU is further supported. The discharge can also be smeared on a slide and sent for a chlamydial comple- Other Complications of ment fixation test for absolute confirmation. Chlamydial Infection

Chlamydia trachomatis is also linked to Reiters Cervicitis and Pelvic Inflammatory Disease syndrome, an inflammatory arthritis of large joints, (PID)

The cervix is a frequent site for Chlamydia trachomatis infection. The inflamed cervix appears red, swollen, and has a yellow mucopurulent endocervical discharge. This infection can spread upwards to involve the uterus, fallopian tubes, and ovaries. This infection, which can be caused by both Chlamydia trachomatis and Neisseria gonorrhoeae, is called pelvic inflammatory disease (PID). Women with PID often develop abnormal vaginal discharge or uterine bleeding, pain with sexual intercourse (dyspareunia), nausea, vomiting, and fever. The most common symptom is lower abdominal pain. The inflamed cervix, uterus, tubes, and ovaries are very painful. Some medical slang emphasizes this. Women are observed to have the "PID shuffle" (small, wide- based steps to minimize shaking of abdomen). With movement of the cervix on bimanual vaginal examination the patient may exhibit the "Chandelier sign" (cervical motion tenderness is so severe that the patient leaps to the chandelier). PID often results in fallopian tube scarring, which can cause infertility, tubal (ectopic) pregnancy, and Figure 12-8

82 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

that commonly occurs in young men between the ages of 20 and 40. Inflammation of the eyes (uveitis and conjunctivitis) and urethritis also occur. However, other infectious agents may also precipitate this syndrome. Fitz-Hugh-Curtis syndrome is an infection of the liver capsule with symptoms of right upper quadrant pain that can occur in men and women. This syndrome is associated with either chlamydial or gonococcal infection.

Lymphogranuloma Venereum Lymphogranuloma venereum, another sexually transmitted disease caused by Chlamydia trachomatis, (serotypes L1, L2 and L3) starts with a painless papule (bump) or ulceration on the genitals that heals sponta- Figure 12-9 neously. The bacteria migrate to regional lymph nodes, which enlarge over the next 2 months. These nodes be- Chlamydia pneumoniae come increasingly tender and may break open and drain (strain TWAR) pus (see Chapter 10, page 69). Chlamydia pneumonia TWAR is a recently identified species ofChlamydia, which is transmitted from person Chlamydia psittaci to person by the respiratory route and causes an atypi- (Psittacosis) cal pneumonia in young adults worldwide (along with Mycoplasma pneumoniae). TWAR is an acronym for its Chlamydia psittaci infects more than 130 species of original isolation in Taiwan and Acute Respiratory. birds, even pet parrots. Humans are infected by inhaling Chlamydia-laden dust from feathers or dried-out feces. This infection is an occupational hazard for breeders of RICKETTSIA carrier pigeons, veterinarians, and workers in pet-shops or poultry slaughterhouses. Infection results in an atyp- Rickettsia is a small, gram-negative, non-motile, rod- ical pneumonia called psittacosis, which occurs 1-3 to coccoid-shaped bacterium. It is similar to Chlamydia weeks after exposure. in that they both are the size of large viruses. Both are obligate intracellular energy parasites (they steal ATP). However, Rickettsia differs from Chlamydia in a num- Atypical Pneumonia ber of ways: Mycoplasma pneumo- Pneumonia caused by viruses, 1) Rickettsia requires an arthropod vector (except for niae, Chlamydia psittaci, and Chlamydia pneumoniae, Q fever). are called atypical pneumonias because the pneumonia is very different from a typical bacterial pneu- Fig. 12-10. Ricky the riding Rickettsia loves to monia caused by Streptococcus pneumonia. Patients travel. He rides a tick in Rocky Mountain spotted fever, with atypical pneumonia present with fever, headache, a louse in epidemic typhus, and a flea in endemic typhus. and a dry hacking cough without production of yellow sputum. The lung exam is surprisingly normal with 2) Rickettsia replicates freely in the cytoplasm, in only a few crackles heard with the stethoscope. The contrast to Chlamydia, which replicates in endosomes chest X-ray may have patches or streaks of infiltrate. (inclusions). In contrast, a patient with a streptococcal pneumonia 3) Rickettsia has a tropism for endothelial cells that appears very sick, coughs up gobs of pus, and has a line blood vessels (Chlamydia likes columnar epithe- lobe of the lung socked in with white blood cells and lium). debris that can be heard on physical exam and seen on 4) They cause different diseases!!! Most Rickettsia chest X-ray. cause rashes, high fevers, and bad headaches.

Fig. 12-9. A man with atypical pneumonia caused by Some Rickettsia share antigenic characteristics with Chlamydia psittaci. He has a bird with a CLAM neck- certain strains of Proteus vulgaris bacteria. It is purely lace, PSITTING on his shoulder. coincidental that they have the same antigens. Proteus

83 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Figure 12-10 is not involved at all in rickettsial disease. The Proteus Fig. 12-11. Antigenic differences among the vulgaris strains that share these common antigens are Rickettsiae. designated OX-2, OX-19, and OX-K. Diagnosis of a rickettsial infection can also be made The Weil-Felix reaction is a classic test that uses with specific serologic tests documenting a rise in anti- these cross-reacting Proteus vulgaris antigens to help Rickettsial antibody titers over time. These include the confirm a diagnosis of a rickettsial infection. This test indirect immunofluorescence test (IFA), the comple- is done by mixing the serum of a patient suspected of ment fixation test (CF), and the enzyme-linked immu- having a rickettsial disease, with antigens from speci- nosorbent assay (ELISA). These tests can specifically fic strains of Proteus vulgaris. If the serum has anti- identify species and even subspecies. rickettsial antibodies, latex beads coated with Proteus Therapy for all rickettsial diseases consists primarily antigens will agglutinate, indicating a positive Weil- of doxycycline and chloramphenicol. Felix test. Comparison of the laboratory results with Fig. 12-11 can even help distinguish specific rickettsial diseases. For example, when this test is performed on a Rickettsia rickettsia patient with signs and symptoms of a scrub typhus in- (Rocky Mountain Spotted Fever) fection, a negative OX-19 and OX-2 along with a positive OX-K is confirmatory. Ricky is riding a wood tick

CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Dieae Weil-Feli OX-19 O-2 OX-K Rock Monain + + - poed fee Rickeial po - - - Epidemic ph + - - Endemic ph + - - Bill-Zine dieae +1- - - Scb ph - - + Tench fee ------Q fee Figure 12-11 WEIL-FELIX

Fig. 12-12. Rocky Mountain spotted fever presents organism, Rickettsia rickettsia. This disease is char- within a week after a person is bitten by either the wood acterized by fever, conjunctival redness, severe head- tick Dermacentor andersoni or the dog tick Dermacentor ache, and a rash that initially appears on the wrists, variabilis. Both of these ticks transmit the causative ankles, soles and palms and later spreads to the trunk.

Figure 12-12

85 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

This figure illustrates the spotted Rocky Mountains there is a dramatic response to doxycycline. Elimina- behind a boy with headache, fever, palmar rash, and tion of nearby rodents, which can serve as a reservoir for tick infestation. Rickettsia akari, is important in preventing this disease.

Rocky Mountain spotted fever is more common in the Rickettsia prowazekii southeastern U. S. tick belt than in the Rocky Mountain region. This disease should be called Appalachian spot- (Epidemic Typhus) ted fever, as most cases currently occur in the south At- Ricky is riding a louse... . lantic and south central states such as North Carolina, An epidemic is the sudden onset and rapid spread of South Carolina, Tennessee, and Oklahoma. However, an infection that affects a large proportion of a popula- cases have been reported in nearly every state. tion. Endemic refers to an infectious disease that ex- The organisms proliferate in the endothelial lining of ists constantly throughout a population. Two species of small blood vessels and capillaries, causing small hem- Rickettsia cause typhus. Rickettsia prowazekii causes orrhages and thrombi. The inflammation and damage to an epidemic form, while Rickettsia typhi is responsible small blood vessels explains the conjunctival redness for endemic typhus. Although they have different reser- and skin rash. Although this disease often resolves in voirs and vectors, these are closely related bacteria that about 3 weeks, it can progress to death (especially when cause a similar disease, and infection with one confers antibiotic therapy is delayed). immunity to the other!! Since the tick transmits this bacteria during its 6-10 hours of feeding, early discovery and removal of ticks will prevent infection (Spach, 1993). Fig. 12.14. Prowazekia is Prower!!! With war, over- crowding, and poverty, unsanitary conditions prevail and lice take control, harboring Rickettsia prowazekii. Rickettsia akari The lice transmit the bacteria to humans, causing epi- (Rickettsialpox) demic typhus. Ricky is riding a mite.... This disease wiped out a third of Napoleon's army Fig. 12-13. Rickettsia akari causes rickettsialpox when he advanced on Moscow in 1812, and was respon- and is transmitted to humans via mites that live on sible for more than 3 million Russian deaths in World house mice. Imagine Ricky, with pox marks, playing War I. The last epidemic in the U. S. occurred more than Atari (old type of Nintendo) with his rodent friend 70 years ago. Currently, flying squirrels serve as a matey mouse. reservoir in the southern U. S. Sporadic cases occur Rickettsialpox is a mild, self-limited, febrile disease when lice or fleas from infected squirrels bite humans. that starts with an initial localized red skin bump Clinically, epidemic typhus is characterized by an (papule) at the site of the mite bite. The bump turns into abrupt onset of fever and headache following a 2-week a blister (vescicle) and days later fever and headache de- incubation period. Small pink macules appear around velop, and other vescicles appear over the body (similar the fifth day on the upper trunk and quickly cover the to chickenpox). Although this disease is self-limiting, entire body. In contrast to Rocky Mountain spotted fever, this rash spares the palms, soles, and face. The patient may become delirious or stuporous. Since Rick- ettsia invade the endothelial cells of blood vessels, there is an increased risk of blood vessel clotting leading to gangrene of the feet or hands. This disease will often resolve by 3 weeks, but occasionally is fatal (especially in older patients). Diagnosis would be easy during an epidemic. The poor doctor with Napoleon's retreating forces surely became an expert diagnostician of louse-borne typhus! It is the sporadic case in the southern U.S., transmitted from flying squirrels to humans by louse or flea bites, that is unexpected and thus difficult to diagnose. Close contact with the flying squirrel vector should raise suspicion. Besides tetracycline and chloramphenicol, improved sanitation and eradication of human lice will help con- Figure 12-13 trol epidemics.

86 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

Figure 12-14

Brill-Zinsser Disease cheopis. (This flea was also responsible for transmission of bubonic plague in the past.) For those of you who have referred to the Zinsser Mi- Following a 10-day incubation period, fever, head- crobiology textbook, it is interesting to note that Hans ache, and a flat and sometimes bumpy (maculopapular) Zinsser is credited with correctly postulating that pa- rash develop, just as with epidemic typhus. Although tients who recovered without antibiotic therapy from this disease is milder than that caused by epidemic ty- epidemic louse-borne typhus could still retain the phus, it is still very serious. pathogen Rickettsia prowazekii in a latent state. Occa- Treat with doxycycline or chloramphenicol. Control sionally, it breaks out of its latent state to produce Brill- flea and rat populations. As with the bubonic plague Zinsser disease. However, symptoms are usually milder (Yersinia pestis), we don't want to just kill the rats because (no skin rash) due to the presence of pre-formed anti- the starving fleas would then all move to bite humans!!! bodies from the original infection. Diagnosis is made by demonstrating a rapid early rise in IgG titer specific for Rickettsia tsutsugamushi Rickettsia prowazekii, rather than a rapid rise in IgM, which occurs in the primary infection. (Scrub Typhus, or Tsutsugamushi Fever) It is always important to completely eradicate Rick- Rickettsia tsutsugamushi is found in Asia and the ettsia prowazekii from your patient with sufficient an- southwest Pacific. This disease affected soldiers in the tibiotic therapy because untreated patients may serve South Pacific during World War II and in Vietnam. as a reservoir between epidemics. Rickettsia tsutsugamushi is spread by the bite of larvae (chiggers) of mites. The mites live on rodents, and the Rickettsia typhi larval chiggers live in the soil. (Endemic or Murine Typhus) Fig. 12-15. Ricky is now a South Pacific sumo Ricky is riding a flea... . wrestler named Ricky Tsutsugamushi. He is walking in Endemic flea-borne typhus is similar to epidemic the scrub (scrub typhus) being bitten by chiggers that typhus, yet it is not as severe and does not occur in are on his feet and legs. epidemics. This disease is caused by Rickettsia typhi. Rodents serve as the primary reservoir, and the disease After a 2-week incubation period, there is high fever, is transmitted to humans via the rat flea, Xenopsylla headache, and a scab at the original bite site. Later

87 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

ever, there is now growing evidence that another bacterium may be the etiologic agent: Bartonella henselae. Several studies have now documented high levels of anti-Bartonella henselae antibodies in patients with cat-scratch disease. Bartonella henselae may also be responsible for a disease called bacillary angiomatosis, which involves a proliferation of small blood vessels in the skin and organs of AIDS patients (Margileth, 1993; Zangwill, 1993).

Coxiella burnetii (Q Fever) Coxiella burnetii is unique to the Rickettsia because, like the gram-positive spore formers (Clostridium and Figure 12-15 Bacillus), it has an endospore form. This endospore confers properties to the bacteria that differ from other a flat and sometimes bumpy (maculopapular) rash Rickettsiae: develops. 1) Resistance to heat and drying: Spores may Bartonella (formerly Rochalimaea contaminate milk products so pasteurization temperatures have to be raised to greater than 60°C to kill the quintana) ( Trench Fever) endospores. 2) Extracellular existence: The spore's resistance Trench fever is a louse-borne febrile disease that oc- allows extended survival outside a host cell. However, curred during World War I. The organism responsible like Chlamydia and Rickettsia, growth and division for this disease is Bartonella quintana. Although it is must occur intracellularly using the host's ATP. Rickettsia-like, it has a different genus name because it 3) Non-arthropod transmission: Coxiella burnetii is not an obligate intracellular organism. grows in ticks and cattle. The spores remain viable in This disease was spread in the trenches by the body dried tick feces deposited on cattle hides, and in dried louse. Infected soldiers developed high fevers, rash, cow placentas following birthing. These spores are headache, and severe back and leg pains. After appear- aerosolized and when inhaled cause human disease. ing to recover, the soldier would relapse 5 days later. Spore inhalation rather than an arthropod bite causes Multiple relapses can occur but fatalities are rare. The Q fever. organism's species name, quintana, reflects the charac- 4) Pneumonia: Because the spores are inhaled into teristic 5-day interval between febrile episodes. the lungs, a mild pneumonia similar to that of a My- Notice the similarities here with epidemic typhus coplasma pneumonia often develops. (Rickettsia prowazekii-Prowar Ricky). Both achieve epidemic proportions during war, when filth and poor san- Clinically, abrupt onset of fever and soaking sweats itation lead to lice overgrowth. occur 2-3 weeks after infection, along with a pneumonia. This is the only rickettsial disease that causes FILTH = LICE _ pneumonia and in which there is NO rash. Rickettsia prowazekii (Epidemic typhus) + Bartonella quintana (trench fever) Fig. 12-16. Visualize Carol Burnett (Coxiella burnetti) coughing after inhaling the spores from a cowhide Bartonella (formerly Rochalimaea) and dried placental products in the grass. henselae (Cat-scratch Disease and Bacillary Angiomatosis) Ehrlichia canis and chaffeensis (Ehrlichiosis and Human Ehrlichiosis) Cat-scratch disease occurs following a cat bite or scratch. A regional lymph node or nodes will enlarge Ehrlichia canis is a disease of dogs. This makes sense and the patient may develop low-grade fever and since dogs like to LICK. Dogs get the bacteria from ticks malaise. The disease usually resolves within a few which jump from dog to dog. The ticks can also bite hu- months without complications. mans, transmitting a very close relative of Ehrlichia ca- A motile, gram-negative rod named Afipia fells nis to humans. This bacterium is now called Ehrlichia was originally isolated from affected lymph nodes. How- chaffeensis and causes a disease (called human ehrli-

88 CHAPTER 12. CHLAMYDIA, RICKETTSIA, AND FRIENDS

chiosis) very similar to Rocky Mountain spotted fever. Patients develop high fever and severe headache, but rarely (only 20% of the time) rash (Spach, 1993).

Fig. 12-17. Summary chart of Chlamydia and Rickettsia.

References Margileth AM, Hayden GF. Cat Scratch Disease From Feline Affection to Human Infection. N Engl J Med 1993; 329:53-54. McCormack WM. Current Concepts: Pelvic Inflammatory Dis- ease. N Engl J Med 1994;330:115-119. Spach DH, et al. Tick-borne diseases in the United States. N Engl J Med 1993;329:936-947. Westrom L, et. al. Pelvic inflammatory disease and fertility: a cohort study of 1,844 women with laparoscopically verified Figure 12-16 disease and 657 control women with normal laparoscopic results. Sex Transm Dis 1992;19:185-92. Zangwill KM, et al. Cat Scratch Disease in Connecticut: Epi- demiology, Risk Factors, and Evaluation of a New Diag- nostic Test. N Engl J Med 1993;329:8-13.

89 Figure 12-17 GRAM-NEGATIVE OBLIGATE INTRACELLULAR PARASITES: CHLAMYDIA AND RICKETTSIA Gla dwin a nd B T rattle r Clinical Microbiology Made Ridiculously Simple CHAPTER 13. SPIROCHETES

Spirochetes are tiny gram-negative organisms that look Stage Clinical like corkscrews. They move in a unique spinning mo- Primary stage Painless chancre (ulcer) ion via 6 thin endoflagella called axial filaments, Secondary stage 1. Rash on palms and soles which lie between the outer membrane and peptidogly- 2. Condyloma latum can layer and wrap around the length of the spirochete. 3. CNS, eyes, bones, kidneys These organisms replicate by transverse fission. and/or joints can be involved Spirochetes are a diagnostic problem. They cannot Latent syphilis 25% may relapse and develop be cultured in ordinary media, and although they have secondary stage symptoms again gram-negative cell membranes, they are too small to Tertiary stage 1. Gummas of skin and bone be seen using the light microscope. Special proce- 2. Cardiovascular (aortic aneurysm) dures are required to view these organisms, including 3. Neurosyphilis darkfield microscopy, immunofluorescence, and silver Figure 13-1 SYPHILIS: CLINICAL stains. Also, serologic tests help screen for infections with spirochetes. MANIFESTATIONS Spirochetes are divided into 3 genera: 1) Treponema, Fig. 13-2. The chancre can be described as a firm, ul- 2) Borrelia, and 3) Leptospira. cerated painless lesion with a punched-out base and rolled edges. It is highly infectious, since Treponema TREPONEMA pallidum sheds from it continuously. Think of this skin ulcer as a small Treponema pallidum resort swimming Treponemes produce no known toxins or tissue de- pool, with thousands of vacationers swimming within. structive enzymes. Instead, many of the disease mani- The chancre resolves over 4-6 weeks without a scar, of- festations are caused by the host's own immune ten fooling the infected individual into thinking that the responses, such as inflammatory cell infiltrates, prolif- infection has completely resolved. erative vascular changes, and granuloma formation.

Treponema pallidum (Syphilis) Treponema pallidum is the infectious agent responsible for the sexually transmitted disease syphilis. The number of new cases of syphilis has been increasing since 1956, with more than 100 thousand cases reported in 1990 in the U.S. Black heterosexual men and women living in urban centers are at highest risk for acquiring Figure 13-2 syphilis today. Treponema pallidum enters the body by penetrating Secondary Syphilis intact mucous membranes or by invading through epithelial abrasions. Skin contact with an ulcer infected Untreated patients enter the bacteremic stage, or sec- with Treponema pallidum (even by the doctor's exam- ondary syphilis, often about 6 weeks after the primary ining hand) can result in infection. When infection oc- chancre has healed (although sometimes the manifesta- curs, the spirochetes immediately begin disseminating tions of secondary syphilis occur while the primary chan- throughout the body. cre is still healing). In secondary syphilis, the bacteria If untreated, patients with syphilis will progress multiply and spread via the blood throughout the body. through 3 clinical stages, with a latent period between Unlike the single lesion of primary syphilis, the second stages 2 and 3. stage is systemic, with widespread rash, generalized lymphadenopathy, and involvement of many organs. Fig. 13-1. Stages of syphilis. The rash of secondary syphilis consists of small red macular (flat) lesions symmetrically distributed over Primary Syphilis the body, particularly involving the palms, soles, and mucous membranes of the oral cavity. The skin lesions The primary lesion of syphilis is a painless chancre can become papular (bumpy) and even pustular. that erupts at the site of inoculation 3-6 weeks after the A second characteristic skin finding of the second initial contact. Regional nontender lymph node swelling stage is called condyloma latum. This painless, wart- occurs as well. like lesion often occurs in warm, moist sites like the

91 CHAPTER 13. SPIROCHETES

vulva or scrotum. This lesion, which is packed with spirochetes, ulcerates and is therefore extremely contagious. Skin infection in areas of hair growth results in patchy bald spots and loss of eyebrows. During the secondary stage, almost any organ can become infected (including the CNS, eyes, kidneys, and bones). Systemic symptoms, such as generalized lymphadenopathy, weight loss, and fever, also occur during this stage. The rash and condyloma lata resolve over 6 weeks, and this disease enters the latent phase.

Latent Syphilis In this stage, the features of secondary syphilis have resolved, although serologic tests remain positive. Most patients are asymptomatic during this period, although about 25% will have one or more relapses and develop the infectious skin lesions of secondary syphilis. After 4 Figure 13-3 years, there are generally no more relapses, and this disease is now considered noninfectious (except in pregnant 3) Neurosyphilis occurs in about 8% of untreated women, who can still transmit syphilis to their fetus). cases. The 5 most common presentations of neurosyphi- About one-third of untreated patients will slowly lis are: progress from this stage to tertiary syphilis. The rest a) Asymptomatic neurosyphilis: The patient will remain asymptomatic. is clinically normal, but cerebrospinal fluid tests positive for syphilis. Tertiary Syphilis b) Subacute meningitis: The patient has fever, stiff neck, and headache. Cerebrospinal fluid analy- Tertiary syphilis generally develops over 6-40 years, sis reveals a high lymphocyte count, high protein, with slow inflammatory damage to organ tissue, small low glucose, and positive syphilis tests. blood vessels, and nerve cells. It can be grouped into 3 Note that most bacteria cause an acute meningitis general categories: 1) gummatous syphilis, 2) cardio- with a high neutrophil count, high protein, and low vascular syphilis, and 3) neurosyphilis. glucose. Treponema pallidum and Mycobacterium 1) Gummatous syphilis occurs 3-10 years after the tuberculosis are two bacteria that cause a subacute primary infection in 15%n of untreated patients. meningitis with a predominance of lymphocytes. c) Meningovascular syphilis: The spirochetes Fig. 13-3. Gummas (Gummy bears) are localized attack blood vessels in the brain and meninges (cir- granulomatous lesions which eventually necrose and cle of Willis!), resulting in cerebrovascular occlusion become fibrotic. These noninfectious lesions are found and infarction of the nerve tissue in the brain, mainly in the skin and bones. Skin gummas are pain- spinal cord, and meninges, causing a spectrum of less solitary lesions with sharp borders, while bone le- neurologic impairments. sions are associated with a deep gnawing pain. These d) Tabes dorsalis: This condition affects the will resolve with antimicrobial therapy. spinal cord, specifically the posterior column and dorsal roots. 2) Cardiovascular syphilis occurs at least 10 years after the primary infection in 10% of untreated Fig. 13-4. Syphilitic tabes dorsalis involves damage patients. Characteristically, an aneurysm forms in the to the posterior columns and dorsal roots of the spinal ascending aorta or aortic arch. This is caused by chronic cord. Posterior column damage disrupts vibratory and inflammatory destruction of the small arterioles (vasa proprioceptive sensations, resulting in ataxia. Dorsal vasorum) supplying the aorta itself, leading to necrosis root and ganglia damage leads to loss of reflexes and of the media layer of the aorta. The wall of the aorta loss of pain and temperature sensation. splits as blood dissects through the weakened media layer. Aortic valve insufficiency and occlusion of the e) General paresis (of the insane): This is a pro- coronary arteries may also develop as the dissection gressive disease of the nerve cells in the brain, lead- spreads to involve the coronary arteries. Antimicrobial ing to mental deterioration and psychiatric therapy can NOT reverse these manifestations. symptoms.

92 CHAPTER 13. SPIROCHETES

2) Bone and teeth are frequently involved. Periosteal (outer layer of bone) inflammation destroys the cartilage of the palate and nasal septum, giving the nose a sunken appearance called saddle nose. A similar inflammation of the tibia leads to bowing called saber shins. The upper central incisors are widely spaced with a central notch in each tooth ( Hutchinsons teeth) and the molars have too many cusps (mulberry molars). 3) Eye disease such as corneal inflammation can occur. Figure 13-4 Interestingly, Treponema pallidum infection does not The Argyll-Robertson pupil may be present in damage the fetus until the fourth month of gestation, so both tabes dorsalis and general paresis. The Argyll- treating the mother with antibiotic therapy prior to this Robertson pupil, caused by a midbrain lesion, constricts time can prevent congenital syphilis. during accommodation (near vision) but does not react to light. This is also referred to as the "prostitutes Diagnostic Tests for Syphilis pupil" because the prostitute accommodates but does not react, and is frequently infected with syphilis. Absolute diagnosis during the first and second stages can be made by direct examination, under darkfield mi- Fig. 13-5. Overview of primary, secondary, latent, croscopy, of a specimen from the primary chancre, the and tertiary syphilis. Notice the rule of sixes: maculopapular rash, or the condyloma latum. Darkfield Six-Sexual transmission microscopy reveals tiny helically-shaped organisms 6 axial filaments moving in a corkscrew-like fashion. 6 week incubation Since direct visualization of spirochetes is effective 6 weeks for the ulcer to heal only during the active stages of primary and secondary 6 weeks after the ulcer heals, secondary syphilis syphilis, serologic tests were developed as a screening develops tool. There are 2 types of serologic screening test: non- 6 weeks for secondary syphilis to resolve specific and specific. 66% of latent stage patients have resolution (no tertiary syphilis) 1) Nonspecific treponemal tests: Infection with 6 years to develop tertiary syphilis (at the least) syphilis results in cellular damage and the release into the serum of a number of lipids, including cardiolipin Congenital Syphilis and lecithin. The body produces antibodies against these antigens. We therefore quantitatively measure Congenital syphilis occurs in the fetus of an infected the titer of the antibodies that bind to these lipids. If a pregnant woman. Treponema pallidum crosses the placental blood barrier, and the treponemes rapidly dis- patients serum has these antibodies, we suspect that seminate throughout the infected fetus. Fetuses that he/she has syphilis. Since invasion of the cerebrospinal acquire the infection have a high mortality rate (still- fluid (CSF) by syphilis also stimulates an increase of birth, spontaneous abortion, and neonatal death), and these anti-lipoidal antibodies, we can also perform this almost all of those that survive will develop early or late test on the CSF to diagnose neurosyphilis. The two most common tests employing this technique are the Vene- congenital syphilis. real Disease Research Laboratory (VDRL) and Early congenital syphilis occurs within 2 years Rapid Plasma Reagin (RPR) test. and is like severe adult secondary syphilis with wide- So why are these tests nonspecific? It is important to spread rash and condyloma latum. Involvement of the realize that 1% of adults without syphilis will also have nasal mucous membranes leads to a runny nose called these antibodies, resulting in a false positive test. For the "snuffles." Lymph node, liver, and spleen enlarge- example, false positive tests often occur in patients who ment, and bone infection (osteitis-seen on X-ray), are are pregnant, have an acute febrile illness such as in- also common afflictions of early congenital syphilis. fectious mononucleosis or viral hepatitis, use intra- Late congenital syphilis is similar to adult tertiary venous drugs, or following immunization. Therefore, a syphilis except that cardiovascular involvement rarely positive nonspecific test must be confirmed with a specific treponemal antibody test. occurs: 2) Specific treponemal tests: While the nonspe- 1) Neurosyphilis is the same as adults and eighth cific tests look for anti-lipoidal antibodies, the specific nerve deafness is common. treponemal tests look for antibodies against the spiro-

93 SEXUAL CONTACT

34 WEEK INCUBATION

PRIMARY SYPHILIS

ULCER HEALS AFTER 4-6 WEEKS

6 WEEKS

SECONDARY SYPHILIS

SYMPTOMS LAST 2-6 WEEKS

HAIR LOSS EVER, WEIGHT LOSS 25% F G ENERALIZED LYMPHADENOPATHY RELAPSE AND RED RASH (ESPECIALLY PALMS TO AND SOLES) SECONDARY CONDYLOMA LATUM

RESOLUTION

Figure 13-5

CHAPTER 13. SPIROCHETES

chete itself. The Indirect Immunofluorescent Tre- VDRL or RPR FTA-ABS Interpretation ponemal Antibody-Absorption (FTA-ABS) test is + + I ndicates an active the most commonly used specific treponemal test. This treponemal infection test is performed by first mixing the patient's serum + - Probably a false positive with a standardized nonpathogenic strain of Tre- - + Successfully treated ponema, which removes (absorbs) antibodies shared by syphilis both Treponema pallidum and the nonpathogenic treponemal strains (as nonpathogenic strains of Tre- - - Syphilis unlikely, although: ponema are part of the normal human flora). The 1. Patients with a syphilis remaining serum is then added to a slide covered with infection who also have AIDS killed Treponema pallidum (as the antigen). Antibodies may be sero-negative that are specific to this organism will subsequently 2. Patient recently infected bind, giving a positive result. with syphilis may not have Since we all have antibodies to nonpathogenic strains developed an immune of treponemes, the absorption part of the FTA-ABS test response yet is necessary to cut down on the number of false posi- Note: VDRL and RPR are very similar tests. tives. Only people who have antibodies specific for the Figure 13-6 SYPHILIS SEROLOGY INTER- pathogenic strain of treponemes will elicit a positive re- PRETATION action. However, false positives can occur with other spirochetal infections, such as yaws, pinta, leptospiro- otics are started. Symptoms include a mild fever, chills, sis, and Lyme disease. malaise, headache, and muscle aches. The killed organ- Treatment isms release a pyrogen (fever-producing enzyme) that is thought to cause these symptoms. This self-limiting re- Treponema pallidum is extremely fragile, and can be action, called the Jarisch-Herxheimer phenome- killed easily with heat, drying, or soap and water. Since non, may occur with most spirochetes. syphilis was found to be treatable by raising one's body temperature, patients in the early 1900's were placed in Treponema pallidum Subspecies a "fever" box (a closed box in the hot sun, with only the patient's head protruding). Fortunately, the discovery There are 3 subspecies of Treponema pallidum (en- of penicillin provided a less hazardous therapy. demicum, pertenue, and carateum) that cause non- The current drug of choice for syphilis is penicillin (the venereal disease (endemic syphilis, yaws, and pinta, particular type and dosage of penicillin depends on the respectively). All 3 subspecies cause skin ulcers and stage of the infection). Penicillin can even cross the pla- gummas of the skin and bones in children, with the ex- centa and cure congenital syphilis. Patients allergic to ception of Treponema carateum, which only causes skin penicillin can be effectively treated with erythromycin discoloration (no gummas). and doxycycline (but doxycycline cannot be used to treat Interestingly, these subspecies are morphologically congenital syphilis, as it is toxic to the fetus). and genetically identical to Treponema pallidum, yet do It is important to realize that reinfection can occur. not cause the sexually transmitted disease syphilis. This suggests that antitreponemal antibodies are not However, the diseases do share many characteristics protective. Cell-mediated immunity may play a role in with syphilis. Like syphilis, the general pattern of these the course of syphilis by inducing the regression of the diseases involves a primary skin papule or ulcer devel- lesions of primary and secondary syphilis. oping at the site of inoculation (usually not the genitals). With adequate treatment, the levels of anticardi- This is followed by a secondary stage of widespread skin olipin antibodies will decrease, while the levels of spe- lesions. The tertiary stage is manifested years later by cific antitreponemal antibodies will remain unchanged. gummas of the skin and bones. Unlike tertiary syphilis, Therefore, a person who is adequately treated will even- the tertiary stages of the nonvenereal treponemes do tually manifest (over months to years) a drop in the not involve the heart or central nervous system. VDRL or RPR to nonpositive, while the FTA-ABS will The antibodies produced by these infections will give remain positive. a positive VDRL and FTA-ABS. One intramuscular injection of long-acting penicillin is curative. Fig. 13-6. Interpretation of syphilis serology. Treponema pallidum Subspecies endemicum Jarisch-Herxheimer Phenomenon ( Endemic Syphilis: Bejel) Most patients with syphilis will develop an acute Endemic syphilis occurs in the desert zones of Africa worsening of their symptoms immediately after antibi- and the Middle East and is spread by sharing drinking

95 CHAPTER 13. SPIROCHETES and eating utensils. Skin lesions usually occur in the oral mucosa and are similar to condyloma lata of secondary syphilis. Gummas of the skin and bone may de= velop later.

Treponema pallidum Subspecies pertenue (Yaws) Yaws, a disease of the moist tropics, spreads from person to person by contact with open ulcers. At the initial site of inoculation a papule appears that grows over months, becoming wartlike and is called the "mother yaw." Secondary lesions appear on exposed parts of the body and years later tertiary gummas develop in the skin and long bones. Fig. 13-7. The tertiary lesions in yaws often cause significant disfigurement of the face. Imagine JAWS (Yaws) taking a bite out of a person's face.

Treponema pallidum Subspecies carateum (Pinta) Fig. 13-8. Hispanic person with colored red and blue skin lesions, saying, "Por favor, no pinta mi cabeza." Pinta is purely a skin disease limited to rural Latin America. After infection by direct contact, a papule develops which slowly expands. This is followed by a secondary eruption of numerous red lesions that turn blue in the sun. Within a year the lesions become depigmented, turning white. These colored lesions look like someone PAINTED them on. Figure 13-8 BORRELIA The corkscrew-shaped Borrelia are larger than the Borrelia cause Lyme disease (Borrelia burgdorferi) Treponema, and therefore can be viewed under a light and relapsing fever (caused by 18 other species of Bor microscope with Giemsa or Wright stains. relia). Both of these diseases are transmitted by insect vectors. Borrelia burgdorferi (Lyme Disease) Lyme disease is seen in the Northeast, Midwest and northwestern U. S. This is the most commonly reported tick-borne illness in the U. S. When walking in the woods during the summer months, you must be careful of the Ixodes tick. This tiny creature's bite can transfer the agent for Lyme disease, Borrelia burgdorferi. It takes greater than 24 hours of attachment for transfer of the organism, so regular "tick checks" may help prevent infection. The animal reservoir for Borrelia burgdorferi includes the white-footed mouse (as well as other small ro • dents) and the white-tailed deer. The Ixodes ticks pick up the spirochete from these reservoirs and can subse- Figure 13-7 quently transmit them to humans.

96 CHAPTER 13. SPIROCHETES

Stage Clinical Early localized stage Erythema chronicum migrans (ECM) (Stage 1) Early disseminated stage 1. Multiple smaller ECM (stage 2) 2. Neurologic: aseptic meningitis, cranial nerve palsies (Bells palsy), and peripheral neuropathy 3. Cardiac: transient heart block or myocarditis 4. Brief attacks of arthritis of large joints (knee) Late stage 1. Chronic arthritis (stage 3) 2. Encephalopathy Figure 13-9 LYME DISEASE: CLINICAL MANI- FESTATIONS Lyme disease has many features that resemble organ systems: the skin, nervous system, heart, and syphilis, although Lyme disease is NOT sexually trans- joints. Notice that the Lyme juice (drawn as drops of mitted. Both of these diseases are caused by spiro- spirochetes) has begun dripping onto the skin, nervous chetes. The primary stage in both involves a single, system, heart, and joints. This stage can occur after or painless skin lesion (syphilitic chancre and Lyme's ery- at the same time as the first stage. thema chronicum migrans) that develops at the initial The skin lesions in this stage are just ECM again, site of inoculation. In both diseases the spirochetes then but this time there are multiple lesions on the body, spread throughout the body, invading many organ sys- and they are smaller (there's just not enough Lyme tems, especially the skin. Both also cause chronic prob- juice to make them as large as the one in the primary lems years later (tertiary syphilis and late stage Lyme stage). disease). Borrelia burgdorferi can invade the brain, cranial Like syphilis, Lyme disease has been di- nerves, and even motor/sensory nerves. Examples in- Fig. 13-9. clude meningitis, cranial nerve palsies (especially of vided into three stages: 1) early localized stage, 2) early the seventh nerve-a Bell's palsy), and peripheral disseminated stage, and 3) late stage. neuropathies. Early Localized Stage The first stage begins about 10 days after the tick bite and lasts about 4 weeks. It consists of just a skin lesion at the site of the tick bite (called erythema chronicum migrans) along with a flulike illness, and regional lymphadenopathy. Fig. 13-10. Erythema chronicum migrans (ECM) starts off as a red (erythematous) flat round rash, which spreads out (or migrates) over time (chronicum). The outer border remains bright red, while the center will clear, turn blue, or even necrose. Visualize a drop of Lyme juice (drawn as drops of spirochetes) land- ing on the skin and the Lyme acid burning the skin red. With time, the juice spreads out and the erythematous lesion spreads, eventually getting so large that there is not enough juice for the center, so that the center now has normal-looking skin.

Early Disseminated Stage Fig. 13-11. The early disseminated stage involves the dissemination of Borrelia burgdorferi spirochetes to 4 Figure 13-10

97 CHAPTER 13. SPIROCHETES

Figure 13-11

Transient cardiac abnormalities occur in about 10% of in a person who has been exposed to ticks in an area en- patients. The most common abnormality is atrioventric- demic for Lyme disease. ular nodal block (heart block), and less commonly my- I ECM, ocarditis and left ventricular dysfunction. Since the Borrelia cardiac lesions usually resolve in a matter of weeks (es- burgdorferi. pecially with antibiotic therapy), a permanent pace- As culturing this organism from blood and CSF is maker is often unnecessary. very difficult, determination of the levels of anti-Borre- Migratory joint and muscle pain can also occur. About lia burgdorferi antibodies is often helpful in making a 6 months after infection attacks of arthritis can occur. Large diagnosis. The two most effective techniques are en- joints such as the knee become hot, swollen, and painful. zyme-linked immunosorbent assays (ELISA) and West- ern immunoblotting. Late Stage Doxycycline or penicillin family antibiotics are currently the most effective antibiotics for treating this About 10% of untreated patients will develop chronic disease. (Spach, 1993) arthritis that lasts for more than a year. This usually in- Two vaccines have recently been developed for Lyme volves 1 or 2 of the large peripheral joints, such as the disease. Both act by passing antibodies through the knee. Interestingly, many of these patients have the B- individual's blood into the biting tick. The antibodies cell allo-antigen HLA-DR (1 + 4). neutralize bacteria in the tick before they can be trans- Like tertiary syphilis, Lyme disease can lead to mitted to the human. The vaccines are ImuLyme and chronic neurologic damage. An encephalopathy can de- LYMErix. velop characterized by memory impairment, irritability, and somnolence. Borrelia recurrentis Diagnosis and Treatment (Relapsing Fever) Diagnosis primarily depends on the doctor's recogniz- Of 18 different species of Borrelia that can cause re- ing the characteristic clinical findings described above lapsing fever, only Borrelia recurrentis is transmitted to

98 CHAPTER 13. SPIROCHETES

humans via the body louse (Pediculus humanus). The other Borrelia species are transmitted by the tick Or- nithodoros. This tick likes to feed on sleeping campers in the western U.S., especially those who sleep in rodent- infested, rustic mountain cabins. After the Borrelia has been transmitted, via the louse or tick, this bacteria disseminates via the blood. A high fever develops, with chills, headaches and muscle aches. Rash and meningeal involvement may follow. With drenching sweats, the fever and symptoms resolve after 3-6 days. The patient remains afebrile for about S days, but then relapses, developing similar features for another 3-6 days. Relapses will continue to occur, although they will become progressively shorter and milder as the afebrile intervals lengthen.

Antigenic Variation: the Key to Relapsing Fever Fig. 13-12. "Why the relapses?" you ask. Well, check out our friend, Boris the Borrelia, who is a master at the art of "antigenic variation." He is initially well cam- ouflaged in blood, but antibodies are soon manufac- tured by the host's immune system. These antibodies can bind specifically to the Borrelia surface proteins and thereby remove the Borrelia from the blood. But sneaky Boris rapidly changes his surface proteins, so that the antibodies no longer recognize them. Boris can now safely proliferate without antibody interference, resulting in fever. As soon as the immune system rec- ognizes that there are new foreign proteins in the blood, it churns out a new set of antibodies that are specific for Boris's new surface proteins. But Boris is ready, and quickly changes his surface proteins again. This antigenic variation allows Boris to continue causing relapses for many weeks. Diagnosis is made by drawing blood cultures (culture on special media) during the febrile periods only (as Figure 13-12 blood cultures are often negative when the patient is afebrile). A Wright's or Giemsa-stained smear of peripheral blood during febrile periods may reveal the Leptospira are found all over the world in the urine of spirochete between red blood cells. Dark-field mi- dogs, rats, livestock, and wild animals. These spiro- croscopy is also useful. chetes can penetrate abraded skin or mucous mem- Doxycycline or erythromycin is the treatment of branes when humans come in contact with the urine choice. either directly or by swimming in contaminated water (usually swallowed). LEPTOSPIRA Clinically, there are 2 phases. In the first or lepto- spiremic phase the bacteria invade the blood and CSF, Leptospira are long, thin aerobic spirochetes that are causing an abrupt onset of high spiking temperatures, wound up in a tight coil. They have a hook on one or both headache, malaise, and severe muscle aches (thighs and ends, giving them an "ice tongs" appearance. Currently lower back). Classically, the conjunctiva are red and the Leptospira are divided into 2 species. One of them, Lep- patient experiences photophobia. After about 1 week, tospira interrogans, causes human disease and has been there is a short afebrile period and then the fever and divided by serologic tests into 23 serogroups (sub- earlier symptoms recur. This second or immune groups) and over 240 serovars (sub-subgroups). phase correlates with the appearance of IgM antibod-

99 CHAPTER 13. SPIROCHETES ies. During the second phase patients may develop suits are available. To arrive at your diagnosis, you meningismus, and the cerebrospinal fluid (CSF) exam must integrate the clinical history (animal contact or reveals an elevated white cell count in most patients. swimming in areas shared by animals), symptoms sug- Leptospira interrogans (classically serogroup ictero- gestive of leptospirosis, and lab tests reflecting the af- haemorrhagiae, but can be other serogroups) can cause fected organs (elevated liver function tests and protein a more severe illness called Weil's disease, or infec- in the urine). Treat patients immediately with either tious jaundice, which involves renal failure, hepatitis penicillin or doxycycline. with jaundice, mental status changes, and hemorrhage in many organs. Fig. 13-13. Summary of the spirochetes. Diagnosis is made by culturing (on special media) blood and CSF during the first febrile phase. During the References second phase and months later the organisms can be cultured from the urine. Spach DH, et. al. Tick-borne diseases in the United States. N The only problem is that treatment should be initi- Engl J Med 1993;329:936-947. ated quickly, before any of the above diagnostic test re-

100

ACID-FAST BACTERIA

CHAPTER 14. MYCOBACTERIUM

The Mycobacteria include 2 species that almost every Persons infected with HIV lack the powerful cell- one has heard of: Mycobacterium tuberculosis, which mediated immunity necessary to combat tuberculosis. causes tuberculosis, and Mycobacterium leprae, which With the rise in HN infected persons, we are witness- 1 causes leprosy. Humans are the only species infected ing a rise in tuberculosis. About I3 of HIV infected with these critters. These organisms are thin rods with persons worldwide also harbor Mycobacterium tubercu- lipid-laden cell walls. This high lipid content makes losis! You will confront this villain again and again in them acid-fa on staining. Only Mycobacteria and No- your future career. cardia are acid-fast. This acid-fast bacillus (rod) is an obligate aerobe, In the acid-fast stain, a smear of sputum, for exam- which makes sense as it most commonly infects the ple, is covered with the red stain carbolfuchsin and lungs, where oxygen is abundant. Mycobacterium tuber- heated to aid dye penetration. Acid alcohol (95% ethanol culosis grows very slowly, taking up to 6 weeks for visi- and 3% HCl) is poured over the smear, and then a ble growth. The colonies that form lump together due to counter-stain of methylene blue is applied. The cell wall their hydrophobic lipid nature, resulting in clumped lipids of the Mycobacterium do not dissolve when the colonies on agar and floating blobs on liquid media. acid alcohol is applied, and thus the red stain does not wash off. So acid-fast organisms resist decolorization with acid alcohol, holding fa to their red stain, while bacteria that are not acid-fast lose the red stain and take on the blue. Fig. 14-1. Visualize a fa ed sports car to remember that acid-fast organisms stain red.

Fige 14-2 There is one class of lipid that only acid-fast organisms have and that is involved in mycobacterial virulence-mycosides. The terminology is as follows: 1) Mcolic acid is a large fatty acid. Fig. 14-2. The chemical structure of mcolic acid, which is a large fatty acid. 2) Mcoide is a mycolic acid bound to a carbohy- Fige 14-1 drate, forming a glycolipid. 3) Cod faco is a mycoside formed by the union of Mycobacterium tuberculosis 2 mycolic acids with a disaccharide (trehalose). This my- (Tuberculosis) coside is only found in virulent strains of Mycobac- terium tuberculosis. Its presence results in parallel Worldwide, there are an estimated 10 million new growth of the bacteria, so they appear as cords. Exactly cases of tuberculosis and 3 million deaths from tuber- how the virulence occurs is still unknown, but experi- culosis annually. Tuberculosis is currently on the rise in ments show that cord factor inhibits neutrophil migra- the U.S., particularly involving the elderly (especially in tion and damages mitochondria. Its injection into mice nursing homes), AIDS patients, and the urban poor. results in the release of tumor necrosis factor (TNF or

102 CHAPTER 14. MYCOBACTERIUM

Figure 14-3 cachectin), resulting in rapid weight loss. Tuberculosis CORD (cord factor) attached to his leg (so as not to lose in humans is usually a chronic disease with weight his stick). Notice Mike has a cough and some weight loss. loss that can be mistaken for the cachexia of malignancy. Cord factor might contribute to this weight loss phenomenon. Pathogenesis of Tuberculosis 4) Sulfatides are mycosides that resemble cord factor with sulfates attached to the disaccharide: They in- Mycobacterium tuberculosis primarily affects the hibit the phagosome from fusing with the lysosome that lung but can also cause disease in almost any other tis- contains bacteriocidal enzymes. The facultative intra- sue. The way it spreads and damages the body depends cellular nature of Mycobacterium tuberculosis during on the host's immune response. The organism and the early infection may be partly attributable to the sul- immune system interact as follows: fatides (see Fig. 2-7). 5) Wax D is a complicated mycoside that acts as an 1) Facultative intracellular growth: With the adjuvant (enhances antibody formation to an antigen) first exposure (usually by inhalation into the lungs), the host has no specific immunity. The inhaled bac- and may be the part of Mycobacterium tuberculosis that activates the protective cellular immune system. teria cause a local infiltration of neutrophils and macrophages. Due to the various virulence factors, the Fig. 14-3. To remember the names of the mycosides and phagocytosed bacteria are not destroyed. They multiply their relationship to Mycobacterium tuberculosis, picture and survive in the macrophages. The bacteria cruise the surfing dude Mike (mycosides). He is WAXING (wax through the lymphatics and blood to set up camp in dis- D) his SUrfboard (sulfatides) and has his surfboard tant sites. This period of facultative intracellular exis-

103 CHAPTER 14. MYCOBACTERIUM tence is usually short-lived because the host rapidly ac- 5 mm of induration in patients who are immunocom- quires its prime defense against the acid-fast buggers: promised, such as those with AIDS. cell-mediated immunity. Note that a positive test does not mean that the pa- 2) Cell-mediaed immni: Some of the tient has active tuberculosis; it indicates epoe and macrophages succeed in phagocytosing and breaking infecion to Mcobacterium tuberculosis at some time up the invading bacteria. These macrophages then run in the past. A positive test is present in persons with ac- toward a local lymph node and present parts of the bac- tive infection, latent infection, and in those who have teria to T-helper cells. The sensitized T-cells then been cured of their infection. multiply and enter the circulation in search of M- Fale poiie e: You still must be wary with this cobacterium tuberculosis. When the T-cells encounter test because some people from other countries have had their antigenic target, they release lymphokines that the BCG (bacill Calmee-Gein) accine for tu- serve to attract macrophages and activate them when berculosis. This vaccine is debatably effective in pre- they arrive. These activated macrophages can now de- venting tuberculosis but it causes a positive PPD. stroy the bacteria. It is during this stage that the Fale negaie e: Some patients do not react to macrophage attack actually results in local destruction the PPD even if they have been infected with tubercu- and necrosis of the lung tissue. The necrosed tissue losis. These patients are usually anegic, which looks like a granular creamy cheese and is called means that they lack a normal immune response due caeo necoi. This soft caseous center is sur- to steroid use, malnutrition, AIDS, etc. To determine rounded by macrophages, multinucleated giant cells, whether a patient is anergic or just has not been in- fibroblasts, and collagen deposits, and it frequently cal- fected with tuberculosis, a second injection (either with cifies. Within this granuloma the bacteria are kept at Candida or mumps antigen) is given in the other arm. bay but remain viable. At some point in the future, per- Most people have been exposed to these antigens, so haps due to a depression in the hosts resistance, the only individuals who are anergic will not respond to bacteria may grow again. the Candida or mumps injection with induration after 48 hours. PPD Skin Te Clinical Manifeaion Following induction of cell-mediated immunity The first exposure to Mcobacterium tuberculosis is against Mcobacterium tuberculosis, any additional exposure to this organism will result in a localized de- called primary tuberculosis and usually is a subclini- layed-type hypersensitivity reaction (type IV cal (asymptomatic) lung infection. Occasionally, an hypersensitivity). Intradermal injection of antigenic overt symptomatic primary infection occurs. protein particles from killed Mcobacterium tuberculo- When an asymptomatic primary infection occurs, the acquired cell-mediated immunity will wall off and sis, called PPD (Purified Protein Derivative), results in suppress the bacteria. These defeated bacteria lie dor- localized skin swelling and redness. Therefore, intradermal injection of PPD will reveal whether or not a mant but can later rise up and cause disease. This sec- person has been infeced with Mcobacterium tubercu- ond infection is called secondary or reactivation losis. This is important because many infected individ- tuberculosis. uals will not manifest a clinical infection for years. For the real number crunchers, here are the statistics: When a positive PPD test occurs, you can treat and Close contacts, such as household members, of someone eradicate the disease before it significantly damages the with pulmonary tuberculosis have a 30% chance of being infected. Of all the infected persons, about 5% will de- lungs or other organs. When you have a patient with a low-grade fever and velop tuberculosis in the next 1 or 2 years and 5% will cough, or a patient who has been in contact with people develop reactivation tuberculosis sometime later in life. who have tuberculosis (you, for example, after working So there is a 10% lifetime risk of developing tuberculosis for those infected with Mcobacterium tuberculosis. in the hospital), you will decide to "place a PPD." You inject the PPD intradermally (just barely under the Pima Tbecloi skin so that the skin bubbles up). Macrophages in the skin will take up the antigen and deliver it to the T- 1) Mcobacterium tuberculosis is usually transmit- cells. The T-cells then move to the skin site, release ted via aerosolized droplet nuclei from the aerosolized lymphokines that activate macrophages, and within respiratory secretions of an adult with pulmonary tu- 1-2 days the skin will become red, raised, and hard. A berculosis. This adult will shower the air with these se- positive test is defined as an area of induration (hard- cretions when he coughs, sings, laughs, or talks. ness) that is bigger in diameter than 10 mm after 48 2) The inspired droplets land in the areas of the lung hours (the time it takes for a type IV delayed hyper- that receive the highest air flow: the middle and lower sensitivity reaction to occur). The test is positive at lung zones. Here there will be a small area of pneu-

104 CHAPTER 14. MYCOBACTERIUM

momtis with neutrophils and edema, just like any bac- 2) Symptomatic primary tuberculosis occurs far terial pneumonia. less frequently, more commonly in children, the elderly, 3) Now the bacteria enter macrophages, multiply, and the immunocompromised (especially HIV infected and spread via the lymphatics and bloodstream to the persons). These groups do not have as powerful a cell- regional lymph nodes, other areas of the lungs, and dis- mediated immune system as do healthy adults, so the tant organs. organisms are not suppressed.

Tuberculosis is a confusing disease because so many Fig. 14-5. Overt or manifest primary tuberculosis: different things can happen. As cell-mediated immunity Large caseous granulomas develop in the lungs or other develops, 1) the infection can be contained so that the organs. In the lungs the caseous material eventually patient will not even realize he was infected, or 2) it can liquifies, is extruded out the bronchi, and leaves behind become a symptomatic disease. cavitary lesions, shown here with fluid in the cavities (called "cavitary lesions with air-fluid levels" on chest 1) Asymptomatic primary infection: The cell- X-ray). mediated defenses kick in, and the foci of bacteria become walled off in the caseous granulomas. These Secondary or Reactivation Tuberculosis granulomas then heal with fibrosis, calcification, and scar formation. The organisms in these lesions are de- Most adult cases of tuberculosis occur after the bac- creased in number but remain viable. Tiny tubercles teria have been dormant for some time. This is called (as the granulomas are called) are often too small to be reactivation or secondary tuberculosis. The in- seen even on chest X-ray. Only a PPD will give the bug- fection can occur in any of the organ systems seeded gers away. Sometimes the chest film will suggest recent during the primary infection. It is presumed that a infection by showing hilar lymph node enlargement or temporary weakening of the immune system may pre- calcifications. cipitate reactivation. Many AIDS patients develop tuberculosis in this manner. HIV infected patients who Fig. 14-4. A calcified tubercle in the middle or lower are infected with Mycobacterium tuberculosis have a lung zone is called a Ghon focus. A Ghon focus accom- 10% chance/year of developing reactivation tuberculo- panied by perihilar lymph node calcified granulomas is sis! And 1 /s of HN infected persons are also infected called a Ghon, or Ranke, complex. with Mycobacterium tuberculosis (worldwide)!

Figure 14-4 Figure 14-5

105

CHAPTER 14. MYCOBACTERIUM

5) Skeleal: This usually involves the thoracic and lumbar spine, destroying the intervertebral discs and then the adjacent vertebral bodies (Po dieae). 6) Join: There is usually a chronic arthritis of 1 joint. 7) Cenal neo em: Tuberculosis causes subacute meningitis and forms granulomas in the brain. 8) Milia becloi: Tiny millet-seed-sized tubercles (granulomas) are disseminated all over the body like a shotgun blast. The kidneys, liver, lungs, and other organs are riddled with the tubercles. A chest film will sometimes show a millet-seed pattern throughout the lung. This disease usually occurs in the elderly and in children.

BIG PICTURE: Tuberculosis is usually a chronic disease; it presents slowly with weight loss, low-grade fever, and symptoms related to the organ system infected. Because of its slow course, it may be confused with cancer. When- ever you have an infection of any organ system, tuberculosis will be somewhere on your differential diagnosis list. It is one of the great imitators! Fige 14-6

Risk of Reactivation in all Persons: 10% for Lifetime! Diagnoi Risk of reactivation in HIV infected: 10% per year! 1) PPD kin e: This screening test indicates an Fig. 14-6. The organ systems that can be involved in exposure sometime in the past. tuberculosis: 2) Che X-a: You may pick up an isolated granuloma, Ghon focus, Ghon complex, old scarring in the 1) Plmona becloi: This is the most com- upper lobes, or active tuberculous pneumonia. mon site of reactivation tuberculosis. The infection usu- 3) Spm acid-fa ain and cle: When the ally occurs in the apical areas of the lung around the acid-fast stain or culture are positive, this indicates an clavicles. It normally reactivates in the upper lobe be- active pulmonary infection. cause oxygen tension is the highest there, due to decreased pulmonary circulation, and Mcobacterium The treatment and control of tuberculosis is compli- tuberculosis is an aerobic bacterium. Slowly these areas cated and will be discussed in the mycobacterial antibiotics chapter (see Chapter 18). of infection grow, caseate, liquify, and cavitate. Clini- cally, the patients usually present with a chronic low- grade fever, night sweats, weight loss, and a productive Tbecloi "Rle of Fie" cough that may have blood in it. This slow erosive infection occurs as the host macrophages and T-cells bat- • Droplet nuclei are 5 micrometers and contain 5 M- tle to wall off the bacteria. cobacterium tuberculosis bacilli. 2) Pleal and peicadial infecion: Infection in • Patients infected with Mcobacterium tuberculosis these spaces results in infected fluid collections around have a 5% risk of reactivation in the first 2 years and the lung or heart respectively. then a 5% lifetime risk. 3) Lmph node infecion: Worldwide, this is the Patients with "high five" NW will have a 5+5% risk most common extrapulmonary manifestation of tuber- of reactivation per year! culosis. The cervical lymph nodes are usually involved. They become swollen, mat together, and drain. Lymph node tuberculosis is called cofla. ATYPICAL MYCOBACTERIA 4) Kidne: Patients will have red and white blood cells in the urine, but no bacteria are seen by Gram stain A large group of mycobacteria live in water and soil or grow in culture (remember that Mcobacterium tuber- mostly in the southern U. S. Based on tuberculin reac- culosis takes weeks to grow in culture and are acid-fast). tions specific for these organisms (like the PPD), it This is referred to as eile pia. has been estimated that up to 50% of the southern

106 CHAPTER 14. MYCOBACTERIUM

Figure 14-7 population have been infected subclinically. These bac- Pacific Islands (Hawaii included). Every year in the teria rarely produce an overt infection, and when they U.S. there are close to 200 newly diagnosed cases, usu- do, it is usually a pneumonia milder than pulmonary tually in immigrants. It is unclear why some people are in- berculosis, or a skin granuloma or ulcer (see Fig. 14-11). fected and some are not. Many studies have attempted to infect human volunteers, with little success. Infection One particular organism in this group deserves occurs when a person (who for unknown reasons is sus- mention because it has become an important pathogen ceptible) is exposed to the respiratory secretions or, less in AIDS patients. Mycobacterium avium-intracel- likely, skin lesions of an infected individual. lulare MAI), also called Mycobacterium avium-complex ( The clinical manifestations of leprosy are dependent MAC), usually only infects birds (avium) and other ani- ( on 2 phenomena: 1) The bacteria appear to grow better mals. It has now become one of the major systemic bac- in cooler body temperatures closer to the skin surface. terial infections of AIDS patients, usually late in the 2) The severity of the disease is dependent on the host's course of the disease. In fact, 50% of AIDS patients ex- cell-mediated immune response to the bacilli (which amined at autopsy are found to be infected with MAI. It live a facultative intracellular existence, like Mycobac- is rarely the cause of death; however, it is certainly a terium tuberculosis). harbinger of death as it only strikes when the T-helper count is virtually nonexistent (see Chapter 25). Infection Fig. 14-7. The acid-fast rod Mycobacterium leprae is with MAI results in a chronic wasting illness; the bacte- seen here cooling off on an ice cube. Leprosy involves the ria disseminate everywhere involving the liver, spleen, cooler areas of the body. It damages the skin (sparing bone marrow, and intestine. The intestinal involvment warm areas such as the armpit, groin, and perineum), often results in chronic watery diarrhea. the superficial nerves, eyes, nose and testes. Cell-mediated immunity once again plays an important Mycobacterium leprae role in the pathogenesis of this disease. The cellular im- (Leprosy, also called Hansen's Disease) munity that limits the spread of the bacteria also causes inflammation and granulomas, particularly in skin and Like Mycobacterium tuberculosis, Mycobacterium nerves. Clinically, leprosy is broken up into five subdi- leprae is an acid-fast rod. It is impossible to grow this visions based on the level of cell-mediated immunity, bacterium on artificial media; it has only been grown in which modulates the severity of the disease: the footpads of mice, in armadillos, and in monkeys. It causes the famous disease leprosy. 1) Lepromatous leprosy (LL): This is the severest There are around 6 million persons infected with form of leprosy because patients canNOT mount a cell- Mycobacterium leprae worldwide, with cases focused in mediated immune response to Mycobacterium leprae. It endemic areas such as India, Mexico, Africa, and the is theorized that defective T-suppressor cells (T-S cells)

107 CHAPTER 14. MYCOBACTERIUM

Figure 14-8

Figure 14-9

108 CHAPTER 14. MYCOBACTERIUM

block the T-helper cell's response to the Mycobacterium is intact, so the lepromin skin test is usually positive. leprae antigens. The patient demonstrates localized superficial, uni- Fig. 14-8. Lepromatous leprosy (LL): The defeated lateral skin and nerve involvement. In this form of lep- macrophage is covered with Mycobacterium leprae acid- rosy, there are usually only 1 or 2 skin lesions. They are fast rods, demonstrating the very low cellular immunity. well-defined, hypopigmented, elevated blotches. The The patient with LL cannot mount a delayed hypersensi- area within the rash is often hairless with diminished tivity reaction. LL primarily involves the skin, nerves, or absent sensation, and enlarged nerves near the skin eyes and testes, but the acid-fast bacilli are found every- lesions can be palpated. The most frequently enlarged where (respiratory secretions and every body organ). The nerves are those closest to the skin-the greater auric- skin lesions cover the body with all sorts of lumps and ular, the ulnar (above the elbow), the posterior tibial, thickenings. The facial skin can become so thickened that and the peroneal (over the fibula head). The bacilli are the face looks lionlike (hence, leonine facies). The nasal difficult to find in the lesions or blood. Patients are non- cartilage can be destroyed, creating a saddlenose de- infectious and often spontaneously recover. formity, and there is internal testicular damage (leading The 3 remaining categories represent a continuum to infertility). The anterior segment of the eyes can be- between LL and TL. They are called borderline lep- come involved, leading to blindness. Most peripheral romatous (BL), borderline (BB), and borderline tu- nerves are thickened, and there is loss of sensation in the berculoid (BT). The skin lesions of BL will be more extremities in a glove and stocking distribution. The in- numerous and have a greater diversity of shape than ability to feel in the fingers and toes leads to repetitive those of BT. trauma and secondary infections, and ultimately contrac- The lepromin skin test is similar to the PPD used tion and resorption of the fingers and toes. Lepromatous in tuberculosis. It measures the ability of the host to leprosy will eventually lead to death if untreated. mount a delayed hypersensitivity reaction against antigens of Mycobacterium leprae. This test is more prognostic than diagnostic and is used to place patients on 2) Tuberculoid leprosy (TL): Patients with TL the immunologic spectrum. It makes sense that TL pa- can mount a cell-mediated defense against the bacteria, tients would have a positive cell-mediated immune re- thus containing the skin damage so that it is not exces- sponse and thus a positive lepromin skin test, while LL sive. They will have milder and sometimes self-limiting patients, who cannot mount a cell-mediated immune re- disease. sponse, have a negative response to lepromin. See Chapter 18 for information about the treatment Fig. 14-9. Tuberculoid leprosy: The macrophage gob- of leprosy. bling up the Mycobacterium leprae acid-fast rods demonstrates the high cell-mediated resistance of tu- Fig. 14-10. The spectrum of leprosy. berculoid leprosy. The delayed hypersensitivity reaction Fig. 14-11. Summary of acid-fast bacteria.

Tuberculoid Borderline Lepromatous Number of Single Several Many skin lesions Hair growth Absent Slightly Not affected on skin decreased lesions Sensation in Completely Moderately Not affected lesions of the lost lost extremities Acid fast None Several I nnumerable bacilli in skin scrapings Lepromin Strongly No reaction No reaction skin test positive

(But a glove and stocking peripheral neuropathy, causing hand and feet numbness, is present!) Adapted from American Medical Association Drug evaluations, 6th edition, p. 1547. Figure 14-10 SPECTRUM OF LEPROSY

109

Figure 14-11 ACID FAST BACTERIA M. Gladwin and 6. Trattler, Clinical Microbiolog Made Ridiculousl Simple ®MedMaster BACTERIA WITHOUT CELL WALLS

CHAPTER 15. MYCOPLASMA

The Mycoplasmataceae are the tiniest free-living or- 1) Cold agglutinins: Certain antigens present on ganisms capable of self-replication. They are smaller human red blood cells are identical to antigens of the than some of the larger viruses. Mycoplasmataceae are Mycoplasma pneumoniae membrane glycolipids. Anti- unique bacteria because they lack a peptidoglycan cell bodies to these Mycoplasma pneumoniae antigens cross- wall. Their only protective layer is a cell membrane, react with human red blood cell antigens and which is packed with sterols (like cholesterol) to help agglutinate the red blood cells at 4°C. These antibodies shield their cell organelles from the exterior environ- are thus called cold agglutinins. They develop by the first or second week of the Mycoplasma pneumoniae in- ment. Due to the lack of a rigid cell wall, Mycoplasmat-aceae can contort into a broad range of shapes, from fection, peak 3 weeks after the onset of the illness, and round to oblong. They therefore cannot be classified as slowly decline over a few months. rods or cocci. You can perform this simple test at the bedside. Put The lack of a cell wall explains the ineffectiveness of the patient's blood in a nonclotting tube. After placing antibiotics that attack the cell wall (penicillin, this tube on ice, the blood will clump together if the pa- cephalosporin), as well as the effectiveness of the anti- tient has developed the cold agglutinin antibodies. ribosomal antibiotics erythromycin and tetracycline. Amazingly, when you lift the tube out of the ice, the There are 2 pathogenic species of Mycoplasmat- clumped blood will unclump as it warms in the palm of aceae, Mycoplasma pneumoniae and Ureaplasma your hand. urealyticum. 2) Complement fixation test: The patient's serum is mixed with glycolipid antigens prepared from My- Fig. 15- 1. Mycoplasmataceae surrounded only by a coplasma. A fourfold rise in antibody titer between cell membrane, padded with sterols. Penicillin and acute and convalescent samples is diagnostic of a recent cephalosporin fail to tear down the cell membrane, infection. while they successfully destroy the cell wall of a nearby 3) Sputum culture: Mycoplasmataceae (both M. gram-positive Streptococcus. pneumoniae and U. urealyticum) can be grown on artificial media. These media must be rich in cholesterol and contain nucleic acids (purines and pyrimidines). Mcoplasma pneumoniae After 2-3 weeks, a tiny dome-shaped colony of My- coplasma will assume a "fried-egg" appearance. Mycoplasma pneumoniae causes a mild, self-limited 4) Mycoplasma DNA probe: Sputum samples are bronchitis and pneumonia. It is the number one cause mixed with a labeled recombinant DNA sequence ho- of bacterial bronchitis and pneumonia in teenagers and mologous to that of the mycoplasma. The recombinant young adults. Following transmission via the respira- probe will label mycoplasma DNA if present. tory route, this organism attaches to respiratory epithelial cells with the help of protein P1 (an adhesin This is a self-limiting pneumonia, but erythromycin virulence factor). After a 2-3 week incubation period, and tetracycline will shorten the course of the illness. infected patients will have a gradual onset of fever, sore throat, malaise, and a persistent dry hacking cough. Ureaplasma urealticum This is referred to as walking pneumonia, because ( T-strain Mycoplasma) clinically these patients do not feel very sick. Chest X-ray reveals a streaky infiltrate, which usu- Hold on!!! Why isn't this second species of Mycoplas- ally looks worse than the clinical symptoms and physi- mataceae called "Mycoplasma"? The man who named cal exam suggest. Most symptoms resolve in a week, this tiny organism didn't want you to ever forget that although the cough and infiltration (as seen on X-ray) Ureaplasma loves swimming in urine and produces may last up to 2 months. Although Mycoplasma is a bac- urease to break down urea (so it is "urea-lytic"!). It is terium, the nonproductive cough and the streaky infil- sometimes referred to as a T-strain Mycoplasma, as it trate on the chest X-ray are more consistent with a viral produces Tiny colonies when cultured. (atypical) pneumonia (see Chapter 12, page 83). Ureaplasma urealyticum is part of the normal flora Diagnostic tests include: in 60% of healthy sexually active women and commonly

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CHAPTER 15. MYCOPLASMA

STREPTOCOCCAL PEPTIDOGLYCAN CELL WALL

PENICILLIN

Co Mycoplasma pneumoniae 0h' STEROL PACKED CELL MEMBRANE PENICILLIN

Figure 15-1

infects the lower urinary tract, causing urethritis. Ure- Ureaplasma urealticum can be identified by its abil- thritis is characterized by burning on urination (dy- ity to metabolize urea into ammonia and carbon dioxide. curia) and sometimes a yellow mucoid discharge from Fig. 15-2. Summary of the Mycoplasmataceae. the urethra. Neisseria gonorrhoeae and Chlamdia trachomatis are the other 2 bacteria that cause urethritis (see Chapter 12, page 80).

112 I CHAPTER 15. MYCOPLASMA

113 ANTI-BACTERIAL MEDICATIONS

CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Figure 16-3

Fig. 16-3. P . T . N Figure 16-1 . Y , , S W W II, . - . O , - . F, Mechanism of Action , T , . T . . Y ( C 1) -. Fig. 16-1. T - - - . A - - . T - - - (- . F beta- lactam antibiotics. ). T transpeptidase. Fig. 16-2. P T - . - . , . I - , porins. T beta-lactam ring binds to and competitively inhibits the transpeptidase enzyme. C - , . B , penicillin-binding protein. T - :

1) P . 2) K - . Figure 16-2 3) B (- ).

114 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Resistance to Beta-Lactam Antibiotics Adverse Effects Bacteria defend themselves from the penicillin fam- All penicillins can cause anaphylactic (aller- ily in 3 ways. Gram-positive bacteria and gram-negative gic) reactions. An acute allergic reaction may occur bacteria use different mechanisms: from minutes to hours and is IgE-mediated. Bron- chospasm, urticaria (hives), and anaphylactic shock 1) One way that gram-negative bacteria defend (loss of ability to maintain blood pressure) can occur. themselves is by preventing the penicillin from pene- More commonly, a delayed rash appears several days trating the cell layers by altering the porins. Remem- to weeks later. ber that gram-negative bacteria have an outer lipid All of the penicillin family antibiotics can cause diar- bilayer around their peptidoglycan layer (see Chapter rhea by destroying the natural GI flora and allowing re- 1). The antibiotic must be the right size and charge to sistant pathogenic bacteria (such as Clostridium be able to sneak through the porin channels, and some dificile) to grow in their place. penicillins cannot pass through this layer. Because gram-positive bacteria do not have this perimeter defense, this is not a defense that gram-positives use. Types of Penicillin 2) Both gram-positive and gram-negative bacteria There are 5 types: can have beta-lactamase enzymes that cleave the C-N bond in the beta-lactam ring. 1) Penicillin G: This is the original penicillin discovered by Fleming, who noted that the mold Penicil- lium notatum produced a chemical that inhibited Staphylococcus aureus. Penicillin was first used in humans in 1941. 2) Aminopenicillins: These penicillins offer better coverage of gram-negative bacteria. 3) Penicillinase-resistant penicillins: This group is useful against beta-lactamase (an enzyme that destroys beta-lactam rings) producing Staphylococcus aureus. 4) Anti-Pseudomonal penicillins (including the carboxypemcillins, ureidopenicillins, and monobactams): This group offers even wider coverage against gram- negative bacteria (including Pseudomonas aeruginosa). 5) Cephalosporins: This is a widely used group of antibiotics that have a beta-lactam ring, are resistant to beta-lactamase, and cover a broad spectrum of gram- positive and gram-negative bacteria. Many bacteria produce cephalosporinases, making Figure 16-4 them resistant to many of these drugs.

Fig. 16-4. Beta-lactamase enzyme (depicted here as a Penicillin G cannon) cleaves the C-N bond. Fig. 16-5. Penicillin G is the original G-man of the Gram-positive bacteria (like Staphylococcus aureus) penicillins. There are oral dosage formulations of Peni- secrete the beta-lactamase (called penicillinase in cillin G, but it is usually given intramuscularly (IM) or the secreted form) and thus try to intercept the antibi- intravenously TV. It is usually given in a crystalline otic outside the peptidoglycan wall. form to increase i ts half-life. Gram-negative bacteria, which have beta-lactamase enzymes bound to their cytoplasmic membranes, de- Many organisms have now developed resistance to stroy the beta-lactam penicillins locally in the periplas- the old G-man because he is sensitive to beta-lactamase mic space. enzymes. But there are a few notable times when the G- man is still used: 3) Bacteria can alter the molecular structure of the transpeptidase so that the beta-lactam antibiotic will 1) Pneumonia caused by Streptococcus pneumoniae. not be able to bind. Methicillin-resistant Staphylococcus (However, resistant strains are developing.) aureus (MRSA) defends itself in this way, making it re- Penicillin V is an oral form of penicillin. It is sistant to ALL of the penicillin family drugs. acid stable in the stomach. It is commonly given for

115 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Note that the aminopenicillins are one of the few drugs effective against the gram-positive enterococcus (see Fig. 16-17). Both ampicillin and amoxicillin can be taken orally, but amoxicillin is more effectively absorbed orally so you will frequently use it for outpatient treatment of bronchitis, urinary tract infections, and sinusitis, caused by gram-negative bacteria. IV ampicillin is commonly used with other antibiotics such as the aminoglycosides (gentamicin) for broad gram-negative coverage. In the hospital you will become very familiar with the "Amp-gen" combo! Patients with serious urinary tract infections are often infected with a gram-negative enteric or enterococcus. Amp-gent offers a perfect broad empiric coverage until cultures reveal the exact organism responsible.

Figure 16-6 Figure 16-5

streptococcus pharyngitis caused by group A beta-he- Penicillinase-Resistant Penicillins molytic streptococcus since it can be taken orally. Mehicillin, nafcillin, and oacillin are penicillinase-resistant drugs that can kill Staphlococcus aureus. These are usually given IV. Aminopenicillins Methicillin was highly efficacious against staphylo- (Ampicillin and Amoxicillin) coccal infections, but because of the occurrence of inter- These drugs have a boade pecm than Peni- stitial nephritis, its use has been discontinued in the cillin G, hitting more gram-negative organisms. This United States. You will still hear its name used fre- enhanced gram-negative killing is attributable to better quently in reference to sensitivity testing (e.g. Methi- penetration through the outer membranes of gram-neg- cillin Resistant Staphylococcus aureus). ative bacteria and better binding to the transpeptidase. However, like penicillin G, the aminopenicillins are still Fig. 16-6. This picture will help you remember the inhibited by penicillinase. names of the IV beta-lactamase resistant penicillins: The gram-negative bacteria killed by these drugs in- I me a nasty o with a beta-lactamase ring around clude Escherichia coli and the other enterics (Proteus, its neck. Salmonella, Shigella, etc.). However, resistance has developed: 30% of Haemophilus influenae and many of Nafcillin is the drug of choice for serious Staphlo- the enteric gram-negative bacteria have acquired peni- coccus aureus infections, such as cellulitis, endocarditis, cillinase and are resistant. and sepsis.

11 6 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Fig. 16-8. Pseudomonas, which can cause a devastating pneumonia and sepsis, is resistant to many antibiotics. It is so crafty and sneaky that we need James Bond to help with its elimination. Bond is fortunate to have three excellent weapons for his task. He has his pick of a car (with special weapons and gadgets), a specially trained tick that can home in on its target and suck out the life of the target, or a megaton pipe bomb: Carboxypenicillins: Ticarcillin and Carbenicillin Ureidopenicillins: Piperacillin and mezlocillin. Like ampicillin, these drugs are combined with an aminoglycoside to double up the Pseudomonas killing (synergism). Frequently used combos include "Pip and gent" and "ticar and gent." These drugs are sensitive to penicillinases, and thus most Staphylococcus aureus are resistant. Carbenicillin has certain disadvantages such as lower activity and thus the need for high dosages; high sodium load; platelet dysfunction; and hypokalemia. The parenteral form is currently not available for use in the United States. Replacement with ticarcillin or a ureidopeni- cillin has reduced these problems and provided antibacterial activity.

Figure 16-7. THE CLOX WERE TICKING. Beta-Lactamase Inhibitors ( Clavulanic Acid, Sulbactam, and Tazobactam) The clocks (clox) were ticking. It was only Fig. 16-7. These enzymes are inhibitors of beta-lactamase. They a matter of time before the oral beta-lactamase re- can be given in combination with penicillins to create a sistant penicillins were discovered: Cloxacillin and di- beta-lactamase resistant combination: cloxacillin. Amoxicillin and clavulanic acid = Augmentin There are now oral formulations of nafcillin and (trade name) oxacillin. Ticaricillin and clavulanic acid = Timentin These drugs are not good against gram-negative or- (trade name) ganisms. They are used for gram-positive bacteria, Ampicillin and sulbactam = Unasyn (trade name) especially those that produce penicillinase (Staphylo- Piperacillin and tazobactam = Zosyn (trade name) coccus aureus). These drugs provide broad coverage against the beta- When a patient has an infected skin wound (cellulitis, lactamase producing gram-positives (Staphylococcus impetigo, etc.), you know he most likely has Staphylo- aureus), gram-negatives (Haemophilus influenza), and coccus aureus or group A beta-hemolytic streptococcus. anaerobes (Bacteroides fragilis). Treating with Penicillin G, V, or ampicillin would not cover penicillinase-producing Staphylococcus aureus. The Cephalosporins Treating with one of these penicillinase-resistant agents There are now more than 20 different kinds of will, and if you give him one of the oral agents he can go cephalosporins. How do you become familiar with so home on oral antibiotics. You won't have to take care of many antibiotics? Do not fear. This chapter will teach him around the clock!!! you how to master these drugs! Anti-Pseudomonal Penicillins Fig. 16-9. The cephalosporins have 2 advantages over (Carboxypenicillins and Ureidopenicillins) the penicillins: This group of penicillins has expanded gram- 1) The addition of a new basement makes the beta- negative rod coverage, especially against the difficult- lactam ring much more resistant to beta-lactamases to-destroy Pseudomonas aeruginosa. They are also ac- (but now susceptible to cephalosparinases!). tive against anaerobes (Bacteroides fragilis) and many 2) A new R-group side chain (another antenna-cable gram positives. TV if you will) allows for double the manipulations in

11 7 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Fige 16-8 Note that MRSA (Methicillin Resistant Staphylo- coccus aureus) is resistant to all cephalosporins because it has changed the structure of its penicillin binding protein (transpeptidase). The Enterococci (in. cluding Streptococcus faecalis) are also resistant to cephalosporins. Fig. 16-11. MRSA and the Enterococci are resistant to the cephalosporins. A new cephalosporin has been classified as a fourth. generation antibiotic because it has great gram-negative coverage like the 3rd generation but also has very good Fige 16-9 gram-positive coverage.

the lab. This leads to all kinds of drugs with different The Names! How do you remember which spectrums of activity. cephalosporin is in which group!!??!! The most important thing is to remember the trends and then you can There are 3 major generations of cephalosporins: look in any pocket reference book for the specific drugs first, second, and third. These divisions are based on in each group. However, it is nice to be familiar with the their activity against gram-negative and gram-positive names of individual drugs, and exams often expect you organisms. to be able to recognize them. Here is an easy, although Fig. 16-10. With each new generation of imperfect, way to learn many of them. cephalosporins, the drugs are able to kill an increasing spectrum of gram negative-bacteria. First-Generation At the same time, the newer cephalosporins are less Almost all cephalosporins have the sound cef in their effective against the gram-positive organisms. The names, but the first generation cephalosporins are the Streptococci and Staphylococci are most susceptible to only ones with a PH. To know the first-generation cephalo. first-generation cephalosporins. sporins, you first must get a PH.D. in PHarmacology.

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CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Figure 16-10

cephalothin coats, and your FOXY cousin is drinking TEA in a toast cephapirin (Exceptions: cefazolin, cefadroxil) to your achievement. cephradine cephalexin cefamandole cefaclor Cefazolin is an important first-generation drug that cefuroxime ( Exceptions: cefmetazole, cefonicid, doesn't have a PH. Don't let this faze you! cefprozil, loracarbef) cefoxitin cefotetan (pronounced ce-fo-tea-tan) Second-Generation Third-Generation Fig. 16-12. Second-generation cephalosporins have fam, fa, fur, fox, or tea, in their names. After you get TRI for third (you know, triglycerides, etc.). Most of your PH.D., you would want to gather your family to the third-generation cephalosporins have a T (for tri) in celebrate! The FAMily is gathered, some wearing FUR their names.

119 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

an acute IgE-mediated reaction or the more comm rash, which usually appears weeks later.

"When do we use these antibiotics?" 1) First-generation cephalosporins: Recall Fig, 16-10 showing the excellent gram-positive coverage. First-generation cephalosporins are used as alterna- tives to penicillin for staphylococcal and streptococcal. infections when penicillin cannot be tolerated (allergy).. Surgeons love to give these drugs before surgery prevent infection from the skin. Figure 16-11 2) Second-generation cephalosporins: This group covers more of the gram-negative rods than the first-generation cephalosporins. Cefuroxime has good coverage against both Streptococcus pneumoniae and Haemophilus influenzae. This makes it an ideal agent for community-acquired bacterial pneumonia when the sputum is negative and you don't know what the organism is. (Streptococcus pneumoniae and Haemophilus in. fluenza are common causes of community-acquired pneumonia.) Cefuroxime is also good for sinusitis and otitis media, which are often caused by Haemophilus influenza or Branhamella catarrhalis. Anaerobic coverage: Three second-generation cephalosporins cover anaerobic bacteria, such as Bac teroides fragilis. These can be used for intra-abdominal infections, aspiration pneumonias, and colorectal surgery prophylaxis, all of which involve anaerobic contamination from the GI tract. These 3 drugs are cefotetan, cefoxitin, and cefmetazole

Fig. 16-13. Some of the second-generation cephalo- Figure 16-12 sporins kill anaerobic bacteria, such as Bacteroides fragilis. Study the picture of a fox (cefoxitin) who met (cefmetazole) an anaerobic bug ceftriaxone for tea (cefotetan). ceftazidime (Exceptions: cefixime, cefoperazone, cefpodoxin, cefetamet) 3) Third-generation cephalosporins: These are cefotaxime used for the multi-drug resistant aerobic gram-negative or- ceftizoxime ganisms that cause nosocomial (hospital-acquired) pneumonia, meningitis, sepsis, and urinary tract infections. ceftibuten The fourth generation cefepime is sometimes called an Note that cefotetan (tea) is a second generation drug. extended spectrum 3rd-generation cephalosporin. Think of him as the same but with a little added muscle against Fourth Generation gram-positives and the terrible Pseudomonas aeruginosa There is only one: Ceftazidime, cefoperazone, and cefepime are cefepime the only cephalosporins that are effective against and it is the only cephalosporin with a fep in its name. Pseudomonas aeruginosa. So when you encounter the (Cefpirome is an investigational agent that will also "impossible-to-kill" Pseudomonas: Give it the Taz, the belong in this class.) Fop, and the Fep! Ceftriaxone has the best CSF penetration and covers Adverse Effects the bacteria that frequently cause meningitis. It is the first-line drug for meningitis in neonates, children, and Ten percent of patients who have allergic reactions to adults. Ceftriaxone is also given IM for gonorrhea, as penicillin will also have a reaction to cephalosporins. more Neisseria gonorrhoea have become resistant to Such allergic reactions are the same as with penicillin: penicillin and tetracycline.

120 CHAPTER 16. PENICILLIN-FAMILY ANTIBIOTICS

Fige 16-13

Fige 16-14

121 CHAPTER 1 6. PENICILLIN-FAMILY ANTIBIOTICS

1. Antipseudomonal penicillins 1. Penicillin ih bea-lacamae inhibio A. Ticarcillin A. Agmenin (Amoicillin clalanae) B. Timentin (ticarcillin clavulanate) B. Timenin (Ticacillin clalanae) C. Piperacillin C. Unan (Ampicillin lbacam) D. Zosyn (piperacillin tazobactam) D. Zon (Pipeicillin aobacam) E. Carbenicillin 2. Second geneaion cephalopoin F. Mezlocillin A. Cefoiin 2. Third generation cephalosporins B. Cefoean A. Ceftazidime C. Cefmeaole B. Ceftizoxime 3. Imipenem and Meopenem C. Cefoperazone 3. Imipenem 4. Chloamphenicol 4. Aztreonam 5. Clindamcin 5. Quinolones 6. Meonidaole A. Ciprofloxacin 7. Toafloacin` B. Levofloxacin C. Trovafloxacin Figure 16-16 ANTIBIOTICS 6. Aminoglycosides THAT COVER THE ANAEROBES A. Gentamicin BACTEROIDES B. Tobramycin (INCLUDING C. Amikacin FRAGILIS) Figure 16-15 ANTIBIOTICS Clinical noe: On the wards imipenem is called THAT COVER PSEUDOMONAS a "decerebrate antibiotic" because you dont have to AER UGINOSA think about what bacteria it covers. It covers almost everything!!! Meropenem is a newer carbapenem that is as Imipenem powerful as imipenem. It can be used interchangeably. There is now a new class of beta-lactam antibiotics called Meropenem is stable against dihydropeptidase, so the carbapenems. You need to know one of its members... cilastin is not needed. Meropenem also has a reduced Tell yourself that you are a pen. Read: "Im a pen." potential for causing seizures in comparison with Now picture the pen crossing out all the bacteria that Imipenem. are difficult to treat. The pen (imipenem) can terminate Aztreonam almost all of them. Imipenem ha he boade anibaceial aci- Aeonam i a magic blle fo gam-negaie i of an anibioic knon o man!!! It kills gram- aeobic baceia!!! It is a beta-lactam antibiotic, but it negatives, gram-positives, and anaerobes (even tough is different in that it is a monobactam. It only has the guys like Pseudomonas aeruginosa and Enterococcus). beta-lactam ring, with side groups attached to the ring. S It does not bind to the transpeptidases of gram-positive MRSA, Pseudomonas , - or anaerobic bacteria, onl to the transpeptidase of (Mycoplasma). gam-negaie baceia. Imipenem is stable to beta-lactamases. Because it is Fig. 16-14 A TREE (AzTREonam) has fallen through very small, it can pass through porin channels to the the center of our house, leaving only the square portion periplasmic space. There it can interact with transpeptidase in a similar fashion as the penicillins and (beta-lactam ring) standing, and letting all the air in (aerobic). You can imagine if this happened to your cephalosporins. Unfortunately, with heavy use of this (gram) experience. Aztre- antibiotic some bacterial strains have developed new house it would be a negaie enzymes that can hydrolyze imipenem, and some gram- onam kills gram-negative aerobic bacteria. negative bacteria have squeezed down their porin chan- Aztreonam kills the tough hospital-acquired, multi- nels to prevent its penetration. drug resistant, gram-negative bacteria, including The normal kidney has a dihydropeptidase that Pseudomonas aeruginosa. breaks imipenem down, so a selective enzyme inhibitor Data suggest there is little cross-reactivity with the of this dihydropeptidase is given with imipenem. The bicyclic beta-lactams, so we can use this in penicillin-al- inhibitor is cilastin. lergic patients! Imipenem can cause allergic reactions similar to those Clinical noe: Because this antibiotic only kills of penicillin. This drug also lowers the seizure threshold. gram-negative bugs, it is used (much like the aminogly-

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Mehicillin-eian Vancomcin Staph lococcs ares (MRSA) Mehicillin-eian Vancomcin Staph lococcus epidermidis Eneococci 1. Ampicillin (Gop D Sepococci) 2. Vancomcin hee i no emeging eiance o ancomcin 3. Imipenem and Meopenem 4. Pipeacillin 5. Leofloacin, Toafloacin, Gepafloacin, and Spafloacin F 16-17 ANTIBIOTICS THAT COVER THE DIFFICULT- TO-KILL GRAM-POSITIVE BACTERIA

cosides) along with an antibiotic that covers gram-posi- Recommended Review Articles: tives. The resulting combinations give powerful broad- Hellinger WC, Brewer NS. Carbapenems and Monobactams: spectrum coverage: Imipenem, Meropenem, and Aztreonam. Symposium on anti- vancomycin + aztreonam microbial agents. Mayo Clinic Proc 1999;74:420-434. clindamycin + aztreonam Marshall WF, Blair JE. The cephalosporins. Symposium on antimicrobial agents. Mayo Clin Proc 1999;74:187-195. Fig. 16-15. Antibiotics that cover Pseudomonas Wright, AJ. The penicillins. Symposium on antimicrobial aeruginosa. agents. Mayo Clinic Proc 1999;74:290-307. Fig. 16-16. Antibiotics that cover anaerobic bacteria, *Because of liver toxicity, the FDA advised that including Bacteroides fragilis. trovafloxacin should be reserved for treatment Fig. 16-17. Antibiotics that cover the difficult-to-kill ONLY in patients that meet ALL of the following gram-positive bacteria: methicillin-resistant Staphylo- criteria: coccus aureus (MRSA), the enterococci, and methicillin- Who have been at least one of five types of serious and resistant Staphylococcus epidermidis. life threatening infections listed below that is judged by the treating physician to be serious and life or limb- Fig. 16-18. Summary of the penicillin (beta-lactam) threatening: family antibiotics. • Nosocomial pneumonia (pneumonia acquired in the References hospital) • Community acquired pneumonia Fish DN, Singletary TJ. Meropenem, a new carbapenem an- • Complicated intra-abdominal infections, including tibiotic. Pharmacotherapy 1997; 17:644-669. Fraser KL, Grossman RF. What new antibiotics to offer in the post-surgical infections outpatient setting. Sem Resp Infect 1998; 13:24-35. • Gynecological and pelvic infections Gilbert DN, Moellering RC, Sande MA. The Sanford Guide to • Complicated skin and skin structure infections, in- Antimicrobial Therapy 1998. 28th edition. Antimicrobial cluding diabetic foot infections Therapy Inc. Dallas Texas, 1998. Mandell GL, Bennett JE, Dollin R, eds. Principles and Prac- **The manufacturer has voluntarily withdrawn Grepa- tice of Infectious Diseases; 4th edition. New York: Living- floxacin from the market because of potential risk of stone 1995. cardiovascular events. Owens RC, Nightingale CH, et al. Ceftibuten: An overview. Pharmacotherapy 1997; 17:707-720. Rockefeller University Workshop. Special report: multiple- antibiotic-resistant pathogenic bacteria. N Engl J Med 1994;330:1247-1251.

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Figure 17-2

Figure 17-1

A . T RNA . A - . S , . W - , . B- . W 80S , 70S 2 : 50S () 30S (). (S, 50S + 30S = 70S)

F. 17-1. T .

T 5 . T - 50S , 30S . H 5 :

Fig. 17-2. C . T , CLEan TAG !!! H CLEan TAG Figure 17-3 : C C C L L Fig. 17-3. T - E E , CLE TAG T T . N AG A (AG). W N CLE - - TAG . T - . Y . : CLE - T ( 50S; TAG 30S. ) , -

125 CHAPTER 17. ANTI-RIBOSOMAL ANTIBIOTICS

. T - IM IV .

Chloramphenicol (T "C")

T . I ( I) kills most clinically important bacteria. I "" . G-, -- , even anaerobic bacteria . I Bacteroides fragilis.

Clinical Uses

B , - , :

1) I , , . T - CSF . 2) Y R M - 128. C . Figure 17-4

N: I - widely used. I - . T - U.S.

Adverse Effects

Fig. 17-4. P . N . Y . T 2 . T - - , . T - . T aplastic anemia. A , 1:24,000 1:40,000 .

Fig. 17-5. N . T , (Gray Baby Syndrome). N, , , Figure 17-5

126 CHAPTER 17. ANTI-RIBOSOMAL ANTIBIOTICS

. T (), , , - . Clindamycin C U T NOT - . S ? M - - . S ? W ?!!!? A ! T ( Bacteroides fragilis). S Figure 17-6 - , Fig. 17-6. Visualize a VAN (vancomycin) and a . W GI , - METRO (metronidazole) cruising down the GI tract. - They run over the ulcerative potholes of pseudomembra- . T nous colitis and kill the offending Clostridium dificile. - , - . Linezolid C ("T G L") , , . O Clinical Uses L, G L, - . T - . L 50S ( ). - . T Adverse Effects L - Y must : C (VRE). Pseudomembranous Colitis!!!!! W , - Adverse Effects , - H 27% GI GI . Clostridium difficile, (, ) 18% , - . T - . Erythromycin ; . T - ("A W") . S C U Clostridium dificile . G- 100 N: W - . I , -. Y - . I , - , Mycoplasma, most cases are now caused by the penicillin fam- - Legionella Chlamydia, drugs . . T , E -- . V . GI T Streptococcus pneumoniae, My- . T coplasma pneumoniae, Chlamydia trachomatis Clostridium diffi- ( TWAR), -- cile. M . , - E - !

127 CHAPTER 17. ANTI-RIBOSOMAL ANTIBIOTICS

Tetracycline/Doxycycline ("T T O") T , , C+, M . W , . D . IV tetracycline .

Clinical Uses of Doxycycline T Tet offensive : 1) Venereal diseases caused by Chlamydia trachomatis. 2) W Mycoplasma pneumoniae ( ). Figure 17-7 3) A - Bru- cella Rickettsia ( - , Fig. 17-8). . 4) D . Fig. 17-7. E Le- Adverse Effects gionnaires disease ( C 10). T F . Fig. 17-8. P V I , a wreath . N Tet offensive - : - - 1) T T ( ! T 20- D. C, U. C). A . S GI irritation , Adverse Effects , . T . 2) A , E one of the safest antibiotics, . N . I . Phototoxic dermatitis : . 3) S : 1) C - and hepatic toxicity. T ( GI ) . . 2) R . I - 4) N discolored teeth . . T There are now new drugs in this class (the macrolide 7, antibiotics) such as: clarithromycin, azithromycin, depressed bone growth. D and roxithromycin. They are showing promise in treating the same bugs plus severe staphylococcal in- . fections, H. influenzae, and even coverage of some of the atypical mycobacterium (Mycobacterium avium-intra- Aminoglycosides cellulare, MAI). (A M G) A - () - - A . I . I , - . , .

128 CHAPTER 17. ANTI-RIBOSOMAL ANTIBIOTICS

Figure 17-8 Clinical Uses trum and is good for hospital-acquired (nosocomial) infections that have developed resistance to other drugs In general, aminoglycosides kill aerobic gram-nega-. while doing time in the hospital. tive enteric organisms (the enterics are the bugs that 5) Neomycin has very broad coverage but is too call the GI tract home, such as E. coli and company). toxic, so it can only be used topically for: The aminoglycosides are among the handful of drugs a) Skin infections. that kill the terrible Pseudomonas aeruginosa!!! 6) Netilmicin Most aminoglycosides end with -mycin: b) Preoperative coverage before GI surgery. This 1) Streptomycin is the oldest one in the family. drug is given orally before GI surgery as it cruises Many bugs are resistant to it. down the GI tract, without being absorbed, killing 2) Gentamicin is the most commonly used of all the the local inhabitants. This prevents spilling of or- aminoglycosides. It is combined with penicillins to treat ganisms during surgery into the sterile peritoneal in-hospital infections. There are also many bacterial cavity. strains resistant to this drug. Adverse Effects 3) Tobramycin is good against the terrible Pseudomonas aeruginosa. Here's how we will remember the side effects: Picture 4) Amikacin does not end with mycin (sorry). this huge boxer, a mean guy (Aminoglycoside), and Maybe that is to set it apart. It has the broadest spec- now check out these pictures:

129 CHAPTER 17. ANTIRIBOSOMAL ANTIBIOTICS

Figure 17-10

Figure 17-9

Fig. 17-9. In the eighth round A MEAN GUY deliv- ers a crushing left hook to his opponent's ear, hurling him off balance, ears ringing and head spinning (eighth cranial nerve toxicity: vertigo, hearing loss). The hearing loss is usually irreversible. Fig. 17-10. With his opponent off balance , Amean guy surges upward with a savage right hook into his left side, Figure 17-11 pulverizing his kidney (renal toxicity). Aminoglycosides are renally cleared and can damage the kidney. This can be reversible, so always follow a patient's BUN and creatinine levels, which increase with kidney damage. Spectinomycin (Spectacular Spectinomycin) Fig. 17-11. The opponent drops to the floor, out cold i n a complete neuromuscular blockade, unable to This drug has a name that sounds like an aminogly- move a muscle, or even breathe. This curare-like effect coside, but it is different structurally and biologically. is rare. Its mechanism is similar in that it acts on the 30S ribo- Note: These side effects occur if the dose is very high, some to inhibit protein synthesis, but exactly how is not so when using these in the hospital, the drug level in the known. Group this with the aminoglycosides in the blood is checked after steady state levels have been CLEan TAG mnemonic (see Fig. 17-2) to remember its achieved (usually after the third dose). With appropri- action, but note that it is NOT an aminoglycoside. It is ate blood levels, these agents are generally safe. given as an IM injection.

130 CHAPTER 17. ANTI-RIBOSOMAL ANTIBIOTICS

discharge, you see tiny red (gram-negative) kidney- shaped diplococci inside the white blood cells. Now what? There are many penicillinase-producing and tetracycline-resistant Neisseria gonorrhoeae, but you still have a few antibiotics to chose from: 1) Ceftriaxone (a third generation cephalosporin): Give one shot IM in the butt! Also give doxycycline by mouth for 7 days to get the Chlamydia trachomatis that is hiding in the background in 50% of cases of urethritis! Azithromycin can be used as an alternative to doxycycline. It can be given as a single dose by mouth. Or: 2) Quinolone antibiotics (ciprofloxacin, ofloxacin) get Neisseria gonorrhoeae and are given as one oral dose (along with doxycycline for the Chlamydia). Or: 3) Spectinomycin: Give one shot in the butt! (along with doxycycline for the Chlamydia). Figure 17-12 Adverse Effects Clinical Uses Infrequent and minor. Spectinomycin does NOT cause the vestibular, cochlear, and renal toxicity that Spectinomycin is used to treat gonorrhea, caused by the aminoglycosides do. Neisseria gonorrhoeae, as an alternative to penicillin and tetracycline (doxycycline), since many strains are Fig. 17-14. Summary of anti-ribosomal antibiotics. resistant to these drugs. Fig. 17-12. Mr. Gonorrhoeae, resistant to tetracycline Recommended Review Articles: and penicillin. Alvarez-Elcoro S, Enzler MJ. The macrolides: Erythromycin, Clarithromycin, and Azithromycin. Symposium on antimi- Fig. 17.13. Spectacular spectinomycin treats resis- crobial agents. Mayo Clin Proc 1999;74:613-634. tant Neisseria gonorrhoeae. Edson RS, Terrell CL. The aminoglycosides. Symposium on antimicrobial agents. Mayo Clin Proc 1999;74:519-528. Let's briefly review the treatment of gonococcal ure- Kasten MJ. Clindamycin, Metronidazole, and Chlorampheni- thritis (gonorrhea) since this will incorporate a lot of the col. Symposium on antimicrobial agents. Mayo Clin Proc drugs we have studied. 1999;74:825-833. A patient presents with burning on urination and a Smilak, JD. The tetracyclines. Symposium on antimicrobial purulent penile discharge. When you Gram stain the agents. Mayo Clin Proc 1999;74:727-729.

Figure 17-13

131 Simple ©MedMaster F 17-14 ANTI-RIBOSOMAL DRUGS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously CHAPTER 18. ANTI-TB and ANTI-LEPROSY ANTIBIOTICS

Figure 18-1

TREATMENT OF TUBERCULOSIS teriocidal to Mcobacterium tuberculosis, but the risk of liver toxicity is too great if used for more than 2 months. This chapter will cover the first-line anti-tuberculosis antibiotics and the logical approach to their use. Treatment of PPD Reactors The first-line drugs, in order of their frequency of use, are: These persons may have latent Mcobacterium tuber- Isoniazid (INH) "I saw a culosis in their bodies and might develop a reactivation Rifampin Red tuberculosis. Treatment of PPD reactors is th us pre- Pyrazinamide Pyre-BURNING THE ventive. Isoniazid is usually used alone for 6-12 LIVER" months as prophylactic therapy. Recently, a study Ethambutol showed that a 2 month course of rifampin plus pyrazi- Streptomycin namide was as effective as a 12 month course of isoniazid in PPD positive patients. This is important due to the Fig. 18-1. Isoniazid ("I saw"), Rifampin ("red"), and high rate of non-compliance with a 12 month treatment Pyrazinamide ("pyre"), are first-line anti-tuberculosis regimen. antibiotics that can cause liver damage ("burning the Here is the difficulty: Not all persons who react to the liver"). PPD test should be treated. Some of these persons will When it comes to tuberculosis, you will encounter 2 never develop reactivation tuberculosis and the drugs populations of patients: 1) those with active tuberculo- carry risks!!! sis and 2) those with a reactive PPD skin test, repre- The decision to treat PPD reactors involves balancing senting a latent infection. These 2 populations are the risk of developing isoniazid-induced liver injury treated very differently. against the risk of developing reactivation tuberculosis. Imagine a set of scales. On one side weighs the Treatment of Active Tuberculosis )risk of developing isoniazid-induced hepatitis and on the other side the risk of reactivating the disease tuberculosis. A patient presents with dyspnea, fever, productive cough, and night sweats that have lasted 2 months, along with upper lobe consolidation on chest X-ray. Risk of Isoniazid Hepatitis Acid-fast bacilli are identified from a sputum sample. As indicated below, advancing age and alcohol con- A patient with active pulmonary or extra-pulmonary sumption increase the risk of developing hepatitis from tuberculosis should receive a 6-month or 9-month treat- isoniazid and tip the scales towards not treating. No- ment as follows: tice that under the age of 35 there is virtually no risk of 6-month regimen: 2 months of isoniazid, rifampin, developing hepatitis with isoniazid: and pyrazinamide, followed by 4 months of isoniazid and rifampin. AGE % that develop HEPATITIS 9-month regimen: 9 months of isoniazid and <20 Rare rifampin. 20-34 <0.3% Notice that the 2 regimens differ in the inclusion or 35-49 < 1.2% exclusion of pyrazinamide. Pyrazinamide is rapidly bac- >50 <2.3%

133 CHAPTER 18. ANTI-TB AND ANTI-LEPROSY ANTIBIOTICS

D T A C - Isoniazid-Resistant Organisms (1974). R INH - . T A, A, S A; - Risk of Reactivation Tuberculosis ; F 2 . PPD , 1) C X-, - . , . T 2) I , 4 - PPD (INH, , , , M. tuberculosis , ). . B. - 3) I , - , - ; o. T - eamen. M. tuberculosis will T C D C A . T S N M. tu- 6-12 : berculosis 4-5 . GREATEST RISK OF REACTIVATION: T - an age PPD >_ 5mm: DOT the I's and Cross the T's to Prevent Resistance!!! 1) P HIV . 2) P X- - DOT D O T: H . 3) C - . N: I ( - diec obeaion o ene adheence. N ), PPD , 3 , PPD. I < 5, . . MODERATE RISK: T an age ANTI-TB ANTIBIOTICS PPD 10: I, R, P: 1) P 1) A cae hepaooici: P , , - , , . . M - 2) P 15-20% , 2 . 3-5 - , . 3) P . 2) A ae abobed oall: T 6-9 . T LESS RISK: T age < 35 !!! PPD 10mm: 3) A peneae ino mo ie: T . H- , - - , Isoniazid (INH) , - - . ("I S") T , - LOWEST RISK: T , . W - age < 35: , !!! A PPD > INH 15mm. M.

134 CHAPTER 18. ANTI-TB AND ANTI-LEPROSY ANTIBIOTICS

Adverse Effects 1) What do you think? Hepatotoxicity!!! Alcoholics beware! Alcohol increases the metabolism of INH by the liver, which increases the risk of developing hepatitis and decreases the therapeutic effect. 2) INH increases the urinary excretion and depletion of pyridoxine (vitamin B6), which is needed for proper nerve function. INH will thus lead to decreased B6 levels, characterized by peripheral neuropathy, rash, and anemia. Many Docs routinely give Bs vitamins with INH.

Rifampin Figure 18-2 !`Red") Think Rifampin: Pyrazinamide 1) Red: Body fluids such as urine, feces, saliva, ("Pyre") sweat, and tears are colored a bright red-orange color by The mechanism of action of pyrazinamide is not rifampin. This is not harmful to the patient, but pa- known. tients must be made aware of this or they will discon- tinue the medicine in a panic. Adverse Effects 2) RNA: Rifampin inhibits the DNA-dependent RNA polymerase of the Mycobacterium tuberculosis bugs. Pyrazinamide is hepatotoxic (no kidding?!) This medicine is usually given for no more than 2 months to avoid Adverse Effects liver toxicity. Avoid it in pregnancy (unknown effect on fetus). 1) Hepatitis (much less than INH). 2) Rifampin induces the cytochrome P450 enzyme Ethambutol system (also called the microsomal oxidase system, or ("Ethane-Butane Torch") MOS), so many other drugs are gobbled up by the spruced-up MOS. This results in decreased half-lives Adverse Effects of certain drugs in patients taking rifampin. Some Fig. 18-2. examples: The main side effect of ethambutol is a dose-dependent, reversible, ocular toxicity. Think of an a) Coumadin (an anticoagulant): Blood-thinning effect will be reduced. ethane-butane flame torch, torching an eye. The ocu- b) Oral contraceptives: Women can get pregnant lar toxicity is manifested by: and get breakthrough bleeding! 1) Decreased visual acuity with loss of central vision c) Oral hypoglycemics and corticosteroids are less (central scotomata). effective. 2) Color vision loss. d) Anticonvulsants such as phenytoin (seizures!). Ethambutol is not used in young children because they are not able to report vision deterioration. Adults Rifabutin are tested for visual acuity and color perception at regular intervals. Many doctors instruct their pa- Rifabutin is very similar to rifampin in structure, an- tients to read the fine newspaper print everyday as a tibacterial activity, metabolism, and adverse reactions. self exam. Itis commonly used in the treatment of Mycobacterium auiumintracellulare (MAI). MAI is usually more sensi- Streptomycin tive to rifabutin than rifampin. The same drug-drug interactions of rifampin Streptomycin is in the aminoglycoside family, which should be considered for rifabutin however, rifabutin inhibits protein synthesis at the 30S ribosomal subunit, induces cytochrome P450 less than rifampin. Thus and is given IM or IV. It is ototoxic and nephrotoxic (see rifabutin is helpful in treating patients with tubercu- Chapter 17). Avoid it in pregnant women (can cause losis and HIV. congenital deafness).

135 CHAPTER 18. ANTI-TB AND ANTI-LEPROSY ANTIBIOTICS

Fixed-Dose Combinations Fixed-dose combinations are available as Rifamate (isoniazid and rifampin) and Rifater (isoniazid, rifampin, and pyrazinamide). Such combinations are strongly encouraged for adults who are self-administering their medications because they may enhance adherence, reduce the risk of inappropriate monotherapy, and prevent drug resistance.

Second-line Drugs These can be used when multiple antibiotics are needed for the treatment of multi-drug resistant My- cobacterium. tuberculosis. Para-aminosalicyclic acid Capreomycin sulfate Cycloserine Ethionamide Kanamycin Amikacin (aminoglycoside) Quinolones such as ciprofloxacin and ofloxacin

Treatment of LEPROSY Three drugs are used in the treatment of leprosy: dapsone, rifampin, and clofazimine.

The Rap Zone of Dapsone

Where's your ears? Figure 18-3 There on the floor. Where's your hand? I left it on the door. Come on Doe, look and see, Less severe cases are treated with rifampin and dap. these rappin' clowns got leprosy. sone for 6 months. See anti-tuberculosis medications (page 134), for Hey, you clown! more on rifampin. See the sulfa drugs (Chapter 19) for You left your nose in the car, more on dapsone. Hey, you clown! You left your toes in a bar, Call the doc, to the Rap Zone, Clofazimine Your first-line drug remains dapsone. Fig. 18-3. A clown-faced clown climbs a DNA double And if you dance to this stupid rappin', helix stairway. His outfit is colored red and black: watch your feet as they start a stampin', There's only one thing to help your dancin, 1) Clofazimine works by binding to the DNA of My Time to reach for the drug, rifampin. cobacterium Leprae. It also has anti-inflammatory Their peelin' clown faces look really lean. actions that are helpful in treating the leprosy They're healing faster than can be seen, reactions. As long as they stay close to clofazimine. 2) Clofazimine is a red-colored compound, and when it deposits in the skin and conjunctiva, it colors these Severe cases of leprosy should be treated with ri- tissues red. Any place on the body where there is a lep- fampin, dapsone, and clofazimine for a minimum of 2 rosy lesion, the skin will appear tan to black. Note the years and until patients are acid-fast bacilli negative. clown's red and black outfit.

136 CHAPTER 18. ANTI-TB AND ANTI-LEPROSY ANTIBIOTICS

Leprosy Reactions nisone or clofazimine. However, the treatment of choice is thalidomide. This is the only use of thalidomide that Fifty percent of patients treated for leprosy develop a is condoned in the U.S. because it is a potent teratogen. leprosy reaction. There are 2 types (1 and 2) and both Again, the anti-leprosy antibiotics are NOT to be with- are immune-mediated, possibly in response to the in- drawn! crease in dead organisms with treatment. The reactions involve inflammation of the nerves, testicles, eyes, Fig. 18-4. Summary of antibiotics for Mycobacteria. joints, and skin (erythematous nodules). Type 1 reactions occur only in borderline patients References (BT, BB, BL), and almost always occur during the first year of treatment. The skin lesions of leprosy typically Hopewell PC, Bloom BR. Tuberculosis and other Mycobacter- swell, becoming more edematous, and occasionally ul- ial Diseases. In: Murray JF, Nadel JA, eds. Textbook of Res- piratory Medicine. 2nd ed. Philadelphia: W.B. Saunders Co. cerate. Neuritis can also occur, leading to sensory or mo- 1994:1094-1160. tor nerve loss. The type 1 reaction is thought to be a Isoniazid-associated hepatitis: summary of the report of Tu- delayed hypersensitivity reaction to the dead bacilli. berculosis Advisory Committee and special consultants to When this reaction occurs, patients can be treated with the director, Centers for Disease Control. MMWR 23:97-98, prednisone or clofazimine. It is important that you do 1974. NOT withdraw the anti-leprosy drugs if a leprosy reac- U.S. Department of Health and Human Services, Division of tion occurs. Tuberculosis Elimination, Centers for Disease Control and Type 2 reaction (called Erythema Nodosum Lep- Prevention, American Thoracic Society. Core Curriculum rosum) is associated with borderline lepromatous (BL) on Tuberculosis: What the clinician should know. 3rd Edi- and lepromatous leprosy (LL). Commonly, a painful tion. Atlanta, Georgia, 1994. nodular rash erupts in a previously normal-appearing Van Scoy, Robert, M.D., Wilkowske, Conrad, M.D.; Antituber- culous Agents; Mayo Clin Proc 67:179-187, 1992. area of skin, along with a high fever. Neuritis, orchitis, arthritis, iritis, and lymphadenopathy can occur as well. The type 2 reaction is thought to be an immune com- Recommended Review Article: plex-mediated reaction involving the deposition of the Van Scoy RE, Wilkowske CJ. Antimycobacterial therapy. immune complexes in tissues followed by complement Symposium on antimicrobial agents. Mayo Clin Proc 1999; activation. These patients can also be treated with pred- 74:1038-1048. F 18-4 ANTIBIOTICS FOR MYCOBACTERIUM M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaster CHAPTER 19. MISCELLANEOUS ANTIBIOTICS

Figure 19-1 THE FLUOROQUINOLONE ANTIBIOTICS , , - , - Ciprofloxacin and Family . C 143. T . T - . T Resistance to the Fluoroquinolones safe, L , , - oral , penetrate . W . . R Fig. 19-1. A DNA - -FLOXACIN. T . T - , , FLOCK OF SIN- . NERS. T gyrating . T DNA Adverse Effects , DNA T : . I , 1) S GI (, , , ), - , , - . T flock of sinners , . T .

139 CHAPTER 19. MISCELLANEOUS ANTIBIOTICS

such as Staphylococcus aureus, gram-negatives including Pseudomonas aeruginosa (see Figure 16-15), and even anaerobes such as Bacteroides fragilis. Add the treasure- trove to your list of GORILLA-CILLINS!!! Unfortunately the pirate who buried the treasure left behind a booby trap that exploded when we opened the trove! *Because of liver toxicity, the FDA advised that trovafloxacin should be reserved for treatment ONLY in patients that meet ALL of the following criteria: Who have at least one of five types of serious and life threatening infections listed below that is judged Figure 19-3 by the treating physician to be serious and life or limb-threatening: latter, which follows rapid infusion of vancomycin , there Nosocomial pneumonia (pneumonia acquired in the is often a nonimmunologic release of histamine, resulting in a red rash of the torso and itching skin. Slow in- hospital) fusion over an hour or antihistamine premedication can Community acquired pneumonia prevent this problem. Complicated intra-abdominal infections, including post-surgical infections Vancomycin inhibits the biosynthesis of the gram- Gynecological and pelvic infections positive peptidoglycan at a step earlier than penicillin. Complicated skin and skin structure infections, in- It complexes with D-alanine D-alanine to inhibit cluding diabetic foot infections transpeptidation. Like penicillin, it acts synergisti- cally with the aminoglycosides. **The manufacturer has voluntarily withdrawn Vancomycin is not absorbed orally. We take ad- Grepafloxacin from the market because of potential vantage of this in the treatment of Clostridium dificile risk of cardiovascular events. pseudomembranous colitis. Vancomycin is taken orally, Sparfloxacin has two important side effects that set cruises down the GI tract unabsorbed, and kills the it apart: Clostridium dificile!! With the extensive use of vancomycin, new strains 1) Up to 8% of patients develop mild to severe of multiple drug-resistant gram-positive organisms photosensitivity. have emerged (see page 27). Synercid (quinopristin/ 2) It can prolong the Q-T interval on the EKG, dalfopristin) is a new type of antibiotic that has a wide which can predispose a patient to the arrhythmia Tor- spectrum of activity. It appears to be effective against sades de pointer. most of the multiple drug-resistant strains. 1 Linezolid is another new type of antibiotic in a to- VANCOMYCIN tally new class of agents with activity against gram- positive organisms, including those resistant to other This IV antibiotic has a critical role in the treatment antimicrobials (see Chapter 17). of infectious diseases. It is the opposite of aztreonam, which covers all gram-negative bugs. Vancomycin ANTIMETABOLITES covers ALL GRAM-POSITIVE bugs!!! Even MRSA (methicillin resistant Staphylococcus Trimethoprim and Sulfamethoxazole aureus)!! Nucleotide and DNA formation require tetrahydrofo- Even the Enterococcus (Streptococcus faecalis)!! Even multi-resistant Staphylococcus epidermidis (in late (TH4). Bacteria make their own TH4 and use Para infections of indwelling intravenous catheters). Amino Benzoic Acid (PABA-you know, the stuff in sun- It is also used to treat endocarditis caused by Strepto- screen) to make part of the TH4. People don't make TH4; we get it as a vitamin in our diet. coccus and Staphylococcus in penicillin-allergic patients. Fig. 19-4. The Sulfa drugs look like PABA. Fig. 19-3. A VAN with a + on its side (an ambulance van) is driving out of some IV tubing. It is about to run When you give a person one of the sulfa drugs (e.g., sul- over an ear and hit a peptidoglycan cell wall. The famethoxazole), the bacteria use it, thinking it's PABA. VAN is being driven by an Indian, the red man. This (There isn't much room for higher cortical neurons in a picture helps us remember that VANCOMYCIN is given single-celled creature.) The sulfa drug competitively in- N, kills gram-positive bugs by inhibiting peptidoglycan hibits production of TH4. Since our cells don't make TH4, production, and cause the red man syndrome. In the it doesn't affect us, but it affects the bacteria.

141 CHAPTER 19. MISCELLANEOUS ANTIBIOTICS

Figure 19-4

TH4 gives up carbons to form purines and other meta- T (Tree): Respiratory tree. TMP/SMX covers Strepto- bolic building blocks. After giving up a carbon, it be- coccus pneumoniae and Haemophilus influenzae. It is comes dihydrofolate (TH2) and must be reduced back good for otitis media, sinusitis, bronchitis, and pneumo- to TH4 by the enzyme dihydrofolate reductase. nia, which are frequently caused by these bugs. Trimethoprim looks like the dihydrofolate reductase of M (Mouth): Gastrointestinal tract. TMP/SMX covers bacteria and competitively inhibits this reduction. This gram-negatives that cause diarrhea such as Shigella, inhibits bacterial DNA formation. Salmonella, and Escherichia coli. The big picture here is that trimethoprim P (PEE): Genitourinary tract. TMP/SMX covers uri- (TMP) and sulfamethoxazole (SMX) act synergis- nary tract infections, prostatitis, and urethritis caused tically to kill many gram-positive and gram-nega- by the Enterics (Escherichia coli and clan). tive bacteria. They both inhibit TH4 production SMX (Syndrome): AIDS. TMP/SMX covers Pneumo- but at different steps. cystis carinii pneumonia (PCP). It is given to prevent PCP when CD4+ T-cell counts drop below 200-250. Pharmacokinetics More than 60% of PCP infections are being prevented Oral absorption: Just imagine eating a big chunk of with this prophylactic intervention! It is also given intravenously in high doses for active pneumonia. rotten egg which smells like sulfur. In addition to Pneumocystis carinii, other protozoans Excretion: Because it is excreted in the urine, this is covered by TMP/SMX are Toxoplasma gondii and a good drug for urinary tract infections. To remember Isospora belli. this, think of the pungent smell of sulfur, that rotten egg smell, and then think of the pungent smell of urine Fig. 19-5. Summary of the miscellaneous antibiotics. when you walk by a Porta-Potti at a construction site. Make this smell association, and you won't forget. References Fraser KL, Grossman RF. What new antibiotics to offer in the Adverse Effects outpatient setting. Seminars on Respiratory Infections. 1998;13:24-35. Adverse effects are rare in persons without AIDS. Frieden TR, Mangi RJ. Inappropriate use of oral ciprofloxacin. They include nausea, vomiting, diarrhea, and skin JAMA 264:1438-1440,1990. rashes (drug eruptions). Approximately half of persons Gilbert DN, Moellering RC, Sande MA. The Sanford Guide to with AIDS develop adverse effects on TMP/SMX, in- Antimicrobial Therapy 1998. 28th Edition. Antimicrobial cluding skin rashes and bone marrow suppression. Therapy Inc., Dallas Texas 1998. Giving TMP/SULFA to a patient on warfarin blood thin- Martin SJ, Meyer JM, et al. Levofloxacin and Sparfloxacin: New ner is very dangerous! This drug interaction increases war- quinolone antibiotics. Ann Pharmacother 1998;32: 320-36. farin levels, resulting in a high risk of bleeding. Recommended Review Articles: Clinical Uses Smilack JD. Trimethoprim-Sulfamethoxazole. Symposium on Antimicrobial Agents. Mayo Clin Proc 74:730-734, 1999. TMP/SMX has no anaerobic coverage, but does have Walker RC. The Fluoroquinolones. Symposium on Antimicro- a wide gram-negative and gram-positive coverage (and bial Agents. Mayo Clin Proc 74:1030-1037, 1999. even covers some Protozoans). Study the following Wilhelm MP, Estes L. Vancomycin. Symposium on Anti- mnemonic TMP SMX: microbial Agents, Mayo. Clin Proc 74:928-935, 1999.

142 Figure 19-5 MISCELLANEOUS ANTIBIOTICS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple OMedMaster PART 2. FUNGI

CHAPTER 20. THE FUNGI

As "budding" doctors in the modern world of AIDS, or- Cell all: Surrounding the cell membrane is the cell gan transplantation, and modern chemotherapy, you wall, composed mostly of carbohydrate with some pro- will treat an unprecedented number of immunocompro- tein. Fungal cell walls are potent antigens to the human mised patients. With their lowered cell-mediated im- immune system. munity, there is a dramatic increase in the incidence of Caple: This is a polysaccharide coating that sur- virtually every fungal infection! You will commonly see rounds the cell wall. This antiphagocytic virulence fac- fungi that used to be exceedingly rare. tor is employed b Cpococc neofoman. The Fungi are eucaryotic cells, which lack chlorophyll, so capsule can be visualized with the India ink ain. they cannot generate energy through photosynthesis. They do require an aerobic environment. After dis- Fig. 20-1. It is helpful to organize the human fungal cussing the following crucial terms, we will discuss the diseases by the depth of the skin that they infect. categories of fungi pathogenic to humans. Yea: Unicellular growth form of fungi. These cells can appear spherical to ellipsoidal. Yeast repro- SUPERFICIAL FUNGAL INFECTIONS duce by budding. When buds do not separate, they can form long chains of yeast cells, which are called Piiai eicolo and inea niga are ex- pedohphae. Yeast reproduce at a slower rate than tremely superficial fungus infections, whose pri- bacteria. mary manifestation is pigment change of the skin. Hyphae: Threadlike, branching, cylindrical, tubules Neither of these cause symptoms and will only come composed of fungal cells attached end to end. These to your attention because skin pigment change is grow by extending in length from the tips of the tubules. noted!!! Both are named for their respective skin Molds (also called Mycelia): Multicellular colonies manifestations: composed of clumps of intertwined branching hyphae. Molds grow by longitudinal extension and produce Pityriasis eicolo ( multicolored) spores. Tinea niga (black colored) Spoe: The reproducing bodies of molds. Spores are rarely seen in skin scrapings. 1) Pityriasis versicolor (also called tinea versi- Dimophic fngi: Fungi that can grow as either a color) is a chronic superficial fungal infection which yeast or mold, depending on environmental conditions leads to hypopigmented or hyperpigmented patches and temperature (usually growing as a yeast at body on the skin. With sunlight exposure the skin around the temperatures). patches will tan, but the patches will remain white. This Saprophytes: Fungi that live in and utilize organic matter (soil, rotten vegetation) as an energy source. infection is caused by Malassezia furfur. 2) Tinea nigra is a superficial fungal infection that causes dark brown to black painless patches on the soles FUNGAL MORPHOLOGY of the hands and feet. This infection is caused by Ex- ophiala werneckii. Certain morphologic characteristics serve as virulence factors as well as targets for antifungal antibiotics. Diagnosis of both infections is based on microscopic Cell membane: The bilayered cell membrane is the examination of skin scrapings, mixed on a slide with innermost layer around the fungal cytoplasm. It con- potassium hydroxide (KOH). This will reveal hyphae tains sterols (sterols are also found in the cell mem- and spherical yeast, as the KOH digests nonfungal branes of humans as well as the bacteria Mcoplama). debris. Malaeia can look like spaghetti (hyphae) with Ergosterol is the essential sterol in fungi, while cho- meatballs (spherical yeast). lesterol is the essential sterol in humans. The antibi- Treatment of both consists of spreading dandruff otics amphoeicin B and nain bind to ergosterol shampoo containing selenium sulfide over the skin. and punch holes in the fungal cell membrane, while ke- This is an inexpensive and effective treatment. The top- oconaole inhibits ergosterol synthesis. ical antifungal imidazoles can also be used.

144 CHAPTER 20. THE FUNGI

Figure 20-1

CUTANEOUS FUNGAL INFECTIONS of 2) Tinea cruris (jock itch): Patients develop itchy the SKIN, HAIR, and NAILS red patches on the groin and scrotum. 3) Tinea pedis (athlete's foot): This infection com- The Dermatophytoses monly begins between the toes, and causes cracking and peeling of the skin. Infection requires warmth and mois- Dermatophytoses are a category of cutaneous fungal ture, so it only occurs in those wearing shoes. infections caused by more than 30 species of fungi. The 4) Tinea capitis (scalp): This condition primarily dermatophytic fungi live in the dead, horny layer of the occurs in children. The infecting organisms grow in the skin, hair, and nails (cutaneous layer seen in Fig. 20-1). hair and scalp, resulting in scaly red lesions with loss of These fungi secrete an enzyme called keratinase, which hair. The infection appears as an expanding ring. digests keratin. Since keratin is the primary structural 5) Tinea unguium (onychomycosis) (nails): The protein of skin, nails, and hair, the digestion of keratin nails are thickened, discolored, and brittle. manifests as scaling of the skin, loss of hair, and crum- bling of the nails. To diagnose a dermatophyte infection: The common dermatophytes include Micopom, Tichophon, and Epidemophon. 1) Dissolve skin scrapings in potassium hydroxide 1) Tinea corporis (body): Following invasion of the (KOH). The KOH digests the keratin. Microscopic ex- horny layer of the skin, the fungi spread, forming a ring amination will reveal branched hyphae. shape with a red, raised border. This expanding raised 2) Direct examination of hair and skin with Wood's red border represents areas of active inflammation with light (ultraviolet light at a wavelength of 365nm). Cer- a healing center. This is appropriately called ringworm, tain species of Microsporum will fluoresce a brilliant since it looks like a ring-shaped worm under the skin. green.

145 CHAPTER 20. THE FUNGI

The first-line drugs for treatment of dermatophy- Sporothri schenckii toses are the topical imidazoles. The skin should be (Sporotrichosis) kept dry and exposed to the drying effects of the air (nudity has its advantages!!). Oral griseofulvin is used Fig. 20-2. Spore tricks. Spoohi chenckii is a di- with tinea capitis and tinea unguium. Griseofulvin morphic fungi commonly found in soil and on plants becomes incorporated into the newly synthesized ker- (rose thorns and splinters). Spooichoi, the dis- atin layers, inhibiting the growth of fungi. So the skin ease, is an occupational hazard for gardeners. Following fungi is cleared only after the old keratin has been a prick by a thorn contaminated with Spoohi replaced. chenckii, a subcutaneous nodule gradually appears. This nodule becomes necrotic and ulcerates. The ulcer heals, but new nodules pop up nearby and along the Candida albicans lymphatic tracts up the arm. The last type of cutaneous fungal infection is caused Microscopic examination of this fungus reveals yeast by Candida albicans. Candida can infect the mouth cells that reproduce by budding. Culture at 37C reveals (oral thrush), groin (diaper rash), and the vagina (Can- yeast, while culture at 25C reveals branching hyphae dida vaginitis). It can also cause opportunistic systemic (dimorphism). Treat with oral potassium iodide or am- infections. All these infections will be discussed in more photericin B. So if you are going to POT roses you might detail later in this chapter (page 150). buy some poaim iodide!

SUBCUTANEOUS FUNGAL Phialophora and Cladosporium INFECTIONS (Chromoblastomycosis)

Subcutaneous fungal infections gain entrance to the Fig. 20-3. Visualize a chome-plaed (chomo) body following trauma to the skin. They usually remain fungi blasting califloe a on the skin to help localized to the subcutaneous tissue or spread along you remember the disease Chomoblaomcoi. It lymphatics to local nodes. These fungi are normal soil is a subcutaneous infection caused by a variety of cop- inhabitants and are of low virulence. per-colored soil saprophytes (Phialophoa and Cla-

Figure 20-2

146 CHAPTER 20. THE FUNGI

Figure 20-3 dosporium) found on rotting wood. Infection occurs fol- Knowledge of these geographic areas is important lowing a puncture wound. Initially, a small, violet wart- clinically. For example, Coccidioides has become the like lesion develops. Over months to years, second most common opportunistic infection in AIDS additional violet-colored wartlike lesions arise nearby. patients who have resided in Arizona. So a sick AIDS Clusters of these lesions resemble cauliflower. Skin patient with a history of previous residence in the scrapings with KOH reveal coppe-coloed cleoic Southwest would raise suspicions. bodies. Treat with itraconazole and local excision. Mechanim of Dieae SYSTEMIC FUNGAL INFECTIONS All 3 fungi have a similar disease mechanism. Notice the parallels to tuberculosis. Three fungi that cause systemic disease in humans Like Mcobaceim becloi the 3 fungi are are Hioplama caplam, Blaomce demai- acquired by inhalation. However, unlike Mycobac- tides, and Coccidioide immii. All 3 are dimophic eim becloi, the fungal infections are inhaled fungi. They grow as mycelial forms, with spores, at as a spore form and are never transmitted from per- 25C on Sabourauds agar. At 37C on blood agar, they son to person. Rather, the spores are aerosolized from grow in a yeast form. This dimophim plays a part in soil, bird droppings, or vegetation. Like Mycobacterium human infection. In their natural habitat (the soil) they tuberculosis, once inhaled, local infection in the lung grow as mycelia and release spores into the air. These is followed by bloodstream dissemination. In most spores are inhaled by humans and at the "human tem- infected persons the fungi are destroyed at this point perature" of 37C they grow as yeast cells. by the cell-mediated immune system. Antigenic preparations called coccidioidin and hioplamin are Geogaph like the PPD of Mcobaceim becloi: when injected intradermally in a previously exposed per- Fig. 20-4. Histoplasma and Blaomce are en- son they yield a delayed type hypersensitivity reac- demic to the vast areas that drain into the Mississippi tion which results in localized swelling within 24-48 River. Visualize a fungi pilot firing a rocket that HITS hours. and BLASTS a hole in the Mississippi River. The 3 fungi have 3 clinical presentations:

Fig. 20-5. Coccidioides is endemic to the southwestern 1) Ampomaic: The majority of cases are asymp- U.S. (Arizona, New Mexico, southern California) and tomatic or mild respiratory illnesses that go unreported. northern Mexico. Visualize Mr. Fungus as he COCKS 2) Pnemonia: A mild pneumonia can develop with his pistol in the old SOUTHWEST. fever, cough, and chest X-ray infiltrates. Like tubercu-

14 7 CHAPTER 20. THE FUNGI

Figure 20-4

skin biopsy, etc. The tissue can be examined with silver stain for yeast or can be grown on Sabourauds agar or blood agar. The ie i he ie!!!! Skin tests are not very helpful for diagnosis, as many people have been previously exposed asymptomatically and will have a positive test anyway. Serologic tests can be helpful (complement fixation, latex agglutination). Acute pulmonary histoplasmosis and coccidioidomy cosis usually require no treatment, as the infection is mild. For chronic or disseminated disease, itraconazole or amphotericin B is often required for months! All Bla. omce infections require aggressive amphotericin B or itraconazole treatment.

Summary of Histoplasma, Blastomyces, and Coccidioides LIKE TUBERCULOSIS Inhaled, primary in fection in the lung. Asymptomatic, mild, severe, or chronic lung infections. Figure 20-5 1 Lung granulomas, calcifications, and/or cavitations. losis, granulomas with calcifications can follow resolu- Can disseminate hematogenously tion of the pneumonia. to distant sites. A small percentage of persons will develop a severe Skin test like PPD. pneumonia, and an even smaller group will progress to a chronic cavitary pneumonia, marked by weight loss, UNLIKE TUBERCULOSIS night sweats, and low-grade fevers, much like a chronic No person-to-person transmission. tuberculosis pneumonia. Fungi with spores, NOT acid-fast 3) Dieminaed: Rarely, the hematogenously bacteria. spread fungi can actually cause disseminated disease, such as meningitis, bone lytic granulomas, skin granu- Fig. 20-6. To remember that Coccidioide, Blasto. lomas that break down into ulcers, and other organ le- mce, and Hioplama all are inhaled as spores and sions. This disseminated form commonly occurs in the cause disease in the lungs, skin, bones, and meninges, immunocompromised host. study Cobo Fng. He has poe bullets, cocks All 3 are best diagnosed by obtaining a biopsy of the his gun, then bla and hi the lung, skin, bone, and affected tissue: bronchoscopic biopsy of lung lesions, meninges.

148 CHAPTER 20. THE FUNGI

Fige 20-6

Hioplama caplam: This fungus is found in nature, especially in pigeon Nonencapsulated despite its name. droppings. Following inhalation and local lung in- Present in bird and bat droppings, so outbreaks of fection, often asymptomatic, the yeast spreads via pneumonia occur when cleaning chicken coops or the blood to the brain. There is no geographic clus- spelunking (cave exploring). tering of infections as with the other systemic my- coses. Most cases (3/4) occur in immunocompromised Blaomce demaiide: persons. In fact, almost 10% of AIDS patients develop Fungi are isolated from soil and rotten wood. cryptococcosis. The rarest systemic fungal infection. A subacute to chronic meningitis develops in crypto- When it does cause infection, it is rarely asympto- coccosis with headache, nausea, confusion, staggering matic or mild. Most cases present as chronic dissemi- gait, and/or cranial nerve deficits. Fever and meningis- nated disease with weight loss, night sweats, lung mus can be mild. Cryptococcal meningitis is fatal with- involvement, and skin ulcers. Blastomyces is the hard- out treatment, because cerebral edema progresses to est to get and the hardest to have! eventual brainstem compression. Cryptococcus can also cause pneumonia, skin ulcers, The bLAST to get, and bone lesions like the other systemic fungi. No BLAST to have!!! The key to diagnosis is doing a lumbar puncture and Coccidioide immii: analyzing the cerebrospinal fluid. An India ink stain Commonly causes a mild pneumonia in normal per- shows yeast cells with a surrounding halo, the polysac- sons in the southwestern U.S. charide capsule. This test is positive half of the time. A Common opportunistic infection in AIDS patients more sensitive test is the cryptococcal antigen test, from that area. which detects cryptococcal polysaccharide antigens. Culture will confirm the diagnosis. Cryptococcus neoformans (Cryptococcosis) Fig. 20-7. AIDS and cryptococcosis. Cryptococcus neoformans is a polysaccharide encapsulated yeast (not dimorphic) similar to the previous 3 fungi in that it is inhaled into the lungs and the in- The usual treatment is with amphotericin B and flucy- fection is usually asymptomatic. It differs in that the tosine. Persons require treatment for as long as 6 major manifestation is not pneumonia but rather months with serial lumbar punctures to confirm resolu- meningoencephalitis. tion. AIDS patients may require treatment for life.

149 CHAPTER 20. THE FUNGI

CRPTOCOCCUS NEOFORMANS

EAST FROM C.S.F. STAINED WITH INDIA INK

Figure 20-7 Candida albicans cosa and patches of cottage cheese-appearing white ( Candidiasis) clumps affixed to the vaginal wall. Imidazole vaginal suppositories are helpful. As a physician you will see this yeast everywhere. It is 3) Diaper rash: Warm moist areas under diapers given out like CANDY to humanity: women with vagini- and in adults between skin folds (under breasts for ex tis, babies with diaper rash, AIDS patients, and the list ample) can become red and macerated secondary to goes on. In the normal host, Candida albicans causes 3 Candida invasion. infections that are cutaneous. In the immunocompromised patient, it can cause any of the 3 cutaneous infections, as well as cause invasive systemic disease. In Immunocompromised Patients 4) Esophagitis: Extension of thrush into the esoph In Normal Hosts agus causes burning substernal pain worse with swal lowing. Candida does not infect the esophagus in 1) Oral thrush: Patches of creamy white exudate immune-competent persons! with a reddish base cover the mucous membranes of the 5) Disseminated: Candida can invade the blood mouth. These are difficult to scrape oft' with a tongue stream and virtually every organ. When systemic can blade. Swish and spit preparations of nystatin or am- didiasis is suspected, the retina must be examined with photericin B, or merely sucking on imidazole candies the ophthalmoscope. Multiple white fluffy candidal will resolve this infection. patches occasionally may be visualized. Clinical 2) Vaginitis: There are 20 million cases of "yeast in- Point: Since Candida is normal flora, it is often cul fection" every year in the U. S. alone! Women develop Lured from the urine, sputum, and stool. These can rep- Candida vaginitis more frequently when taking antibi- resent contaminants. However, isolation from the blood otics, oral contraceptives, or during menses and preg- is never normal and must be respected!!! nancy. The symptoms are vaginal itching and discharge Diagnosis is made with KOH preparation of skin (thick copious secretions wetting the underwear). scrapings, or with stains and cultures of biopsied tissue Speculum examination reveals inflamed vaginal mu- or blood.

150 CHAPTER 20. THE FUNGI

Figure 20-8

Systemic infection requires amphotericin B or the Figure 20-9 oral antifungal imidazole called fluconazole. THE FUNGI-LIKE BACTERIA: Aspergillus flavus ACTINOMYCETES and NOCARDIA (Aspergillosis) Fig. 20-10. Actinomycetes are bacteria acting like fungi. These are procaryotic organisms and are truly ASPIRATION of ASPERGILLUS = ASTHMA bacteria. They are discussed here because they fre- Fig. 20-8. The spores of Aspergillus mold are floating quently grow in the form of mycelia and are water and in the air everywhere. Some persons develop an soil saprophytes. The 2 that cause human disease are asthma-type reaction to these spores. They have a type 1 hypersensitivity reaction (IgE-mediated immediate allergic reaction) with bronchospasm, increase in IgE antibodies, and blood eosinophilia. They also manifest a type 4 reaction (delayed type cell-mediated allergic reaction) with cell-mediated inflammation and lung infiltrates. Systemic corticosteroids are an effective treatment. Fig. 20-9. Persons with lung cavitations from tuber, culosis or malignancies can grow an aspergillus fungal ball in the cavity, called an aspergilloma. This ball can be large (as big as a golf ball) and require surgical removal. Immunocompromised hosts can develop invasive pneumonias and disseminated disease. Bloody sputum may occur, due to blood vessel wall invasion by As- pergillus hyphae. Aspergillus flavus and other fungi produce toxins that cause liver damage and liver cancer. These toxins are called mycotoxins. The toxin produced by As- pergillus flavus is called the aflatoxin. This has worldwide significance since Aspergillus grows ubiquitously, contaminating peanuts, grains, and rice. The fact that half of the cancers south of the Sahara desert in Africa are liver cancers and 40% of screened foods contain afla- toxins suggests that this is a real threat. Figure 20-10

151 CHAPTER 20. THE FUNGI

Acinomce and Nocadia, both of which are gram- onl Acinomce forms sulfer granules and onl No positive rods. cadia i acid-fast.

Actinomyces Israelii Nocardia asteroides

There are 4 concep you should know about this Nocadia forms weakly gram-positive, partially organism: acid-fa beaded banching hin filamen! It is not considered normal flora. Infections with Nocadia are 1) It is a gram-positive, beaded, filamentous anaero- frequently misdiagnosed as tuberculosis because it is bic organism that grows as normal flora in the mouth acid-fast and it causes the same disease process. Like and GI tract. Mcobaceim becloi, Nocadia is inhaled and 2) It causes eroding abscesses following trauma to grows in the lung to produce lung abscesses and cavita- the mucous membranes of the mouth or GI tract. The in- tions. Erosion into the pleural space can occur, as well fection is named according to the area of the body as blood-bourne dissemination, resulting in abscesses in through which the abscess erodes: ceicofacial the brain and other organs. Immunocompromised pa- acinomcoi, abdominal acinomcoi, and ho- tients, especially those taking steroids, are particularly acic acinomcoi. at risk for Nocadia infection. Treatment is with 3) When examined under the microscope, the pus imehopim and lfamehoaole. draining from the abscess reveals yellow granules, Treatment ofAcinomce and Nocadia is a SNAP! called lf ganle. These are not composed of Sulfa for sulfur but of microcolonies of Acinomce and cellular Nocardia debris. Actinomyces give 4) Treatment of this gram-positive bacterium is with Penicillin penicillin G and surgical drainage. Noe: Acinomce and Nocadia are both filamen- Fig. 20-11. Summary of the fungi. tors, beaded, branching gram-positive organisms, but

152 Figure 20-11 FUNGI Figure 20-11 (continued) M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple C~MedMaster CHAPTER 21. ANTIFUNGAL ANTIBIOTICS

The number of fungal infections has risen dramatically Adverse Effects with the increase in patients who are immunocompromised from AIDS, chemotherapeutic drugs, and organ On the wards this drug is referred to as am- transplant immunosuppressive drugs. For this reason photerrible and Awfultericin because of its nu- you will frequently use the handful of antifungal an- merous adverse effects: tibiotics available. 1) Renal toxicity: (Poor Mr. Kidney!) There is a Ergosterol is a vital part of the cell membranes of dose-dependent azotemia (increase in BUN and creati- fungi but is not found in the cell membranes of humans, nine reflecting kidney damage) in most patients taking which contain cholesterol. Most antifungal agents bind this drug. This is reversible if the drug is stopped. The more avidly to ergosterol than to cholesterol, thus more creatinine level must be followed closely, and if it be- selectively damaging fungal cells than human cells. By comes too high (creatinine > 3), the dosage may have to binding to or inhibiting ergosterol synthesis, they in- be lowered, terminated, or switched to alternate day crease the permeability of the cell membranes, causing regimens. cell lysis. 2) Acute febrile reaction: A shaking chill (rigors) We can divide antifungal agents into 3 groups: with fever occurs in some people after IV infusion. This 1) Antifungal agents that are used for serious sys- is a common side effect. temic infections: 3) Anemia. Amphotericin B, the grandfather of antifungal 4) Inflammation of the vein ( phlebitis) at the IV site. agents. This drug covers almost all medically impor- These side effects are important because they are tant fungi but must be given intravenously (not ab- very common. In fact, when amphotericin B is given in sorbed orally) and causes many side effects. It may the hospital, it is usually given with aspirin or aceta- also be given intrathecally (into the cerebrospinal minophen to prevent the febrile reaction. Daily BUN fluid). and creatinine levels are drawn to monitor kidney func- Itraconazole, given orally, has now proven use- tion. You can see that these side effects are important ful for many of these infections. in day-to-day clinical management! 2) Antifungal agents that are used for less serious Fig. 21-1. Properties of amphotericin B, the "am- systemic infections: phibian terrorist": i ntravenous drug delivery; fung- The oral azole drugs. The prototype is keto- icidal by binding to ergosterol in the fungal cell mem- conazole. There are now new agents in this class, brane, causing membrane disruption and osmotic lysis called fluconazole and itraconazole ( mentioned of the cell; nephrotoxicity. above). 3) Antifungal agents that are used for superficial To speed amphotericins travel through the kidneys fungal infections: and decrease renal toxicity, hydration with normal Griseofulvin (taken orally) and the many saline is used commonly with traditional amphotericin topical antifungal agents such as nystatin B. This hydration is generally not required with the and the azole drugs (clotrimazole and newer preparations of amphotericin B. Electrolyte re- miconazole). placement is another important adjunct of amphotericin therapy because amphotericin causes increases Amphotericin B in urinary excretion of potassium, magnesium and bicarbonate. The classic antifungal antibiotic is amphotericin B. New preparations of amphotericin B are now available Most species of fungi are susceptible to it, and although that add different lipids (fats!) to the traditional (old fash- it has many side effects, it remains the drug of choice for ion) amphotericin B deoxycholate. The addition of the most serious systemic fungal infections: lipid decreases the nephrotoxicity of the drug, making it Systemic Candida i nfections. less Amphoterrible. Cryptococcal meningitis: used in combination with Amphotericin B colloidal dispersion (ABCD: flucytosine. Amphocil): Ampho B + cholesterol sulfate. Rigors still Severe pneumonia and extrapulmonary Blastomyco- occur but nephrotoxicity is reduced. sis, Histoplasmosis, and Coccidioidomycosis. Amphotericin B lipid complex (ABLC): Ampho Invasive Aspergillosis. B + dimyristoylphosphatidylglycerols and dimyris- Invasive Sporotrichosis. toylphosphatidylcholines. Rigors still occur but there is Mucormycosis less nephrotoxicity.

15,5 CHAPTER 21. ANTIFUNGAL ANTIBIOTICS

Figure 21-1

Liposomal amphotericin B (Ambisome): A unil- wrestling partner of amphotericin B. Amphotericin B amellar liposome containing a mixture of 1 molecule of busts holes in the cell membranes and flucytosine en- amphotericin B surrounded by a coating of nine mole- ters and inhibits DNA/RNA synthesis. cules of lipid (soy lecithin, cholesterol, and dis- Most fungi are resistant to flucytosine, but Crypto- tearoylphosphatidylglycerol), like a coated jaw breaker. coccus and Candida are the exceptions. Flucytosine use There is little nephrotoxicity or rigors. is mostly limited to the treatment of cryptococcal Some hospitals make their own concoction by adding meningitis, in conjunction with Amphotericin B. amphotericin B deoxycholate to Intralipid (parenteral fat for intravenous feeding) in a mixture of 1-2 mg amphotericin B per ml lipid. Less nephotoxicity is seen, but Adverse Effects once again we do not yet know enough about antifungal efficacy. 1) Bone marrow depression, resulting in leukopenia and thrombocytopenia. Remember that most an- timetabolite type drugs will do this (methotrexate, sulfa Flucytosine drugs, 5-fluorouracil, etc.). 2) Nausea, vomiting, diarrhea. This again is com- Flucytosine is rarely used alone because of rapid demon with the antimetabolites, such as the chemothera- velopment of resistance. Think of it as the tag team peutic drugs.

156 I CHAPTER 21. ANTIFUNGAL ANTIBIOTICS

The reason for these adverse effects is that the drugs Fluconazole damage DNA during its formation in rapidly dividing cells such as bone marrow and GI epithelial cells. Fluconazole is one of the triazoles; it is less toxic and has broader antifungal coverage than ketoconazole. Like ketoconazole it is used for cutaneous Candida in- The Azole Family fections but it is also used as a second-line agent behind amphotericin B for systemic candidiasis and cryptococ- The azole family may be classified into 2 groups of cal meningitis. In AIDS patients who have had crypto- drugs: the imidazoles and the triazoles. coccal meningitis, maintenance with fluconazole will prevent relapses. IMIDAZOLES TRIAZOLES The big picture with fluconazole is that it kills Can- Ketoconazole Fluconazole dida albicans very well: Miconazole Itraconazole 1) Studies comparing it to amphotericin B in the Clotrimazole Voriconazole treatment of systemic Candida albicans infection (in non-neutropenic patients) demonstrated equivalent The azoles inhibit the cytochrome P-450 enzyme sys- effcancy. tem, which is involved in ergosterol synthesis. The de- 2) A single dose of fluconazole very effectively clears pletion of ergosterol disrupts the permeability of the candida vaginitis. fungal cell membrane. These drugs are active against a broad spectrum of fungi. Clotrimazole and miconazole are too toxic for sys- Itraconazole temic use and for this reason, are primarily used for This triazole is becoming the next amphotericin B but topical fungal infections, including pityriasis versi- in an oral formulation without the many amphoterrible color, cutaneous candidiasis, and the dermatophytosis side effects!!! (tinea pedis, corporis, etc.). Clotrimazole troches (like Itraconazole is now used as first-line treatment candies) are sucked to treat oral Candida (thrush), and for chromoblastomycosis, histoplasmosis, coccidioido- clotrimazole vaginal suppositories treat Candida mycosis, blastomycosis, and possibly for invasive vaginitis. aspergillosis. The main problem with this drug is Ketoconazole, fluconazole, and itraconazole are poor oral absorption. Taking it with acid drinks tolerated orally and have many important uses for sys- such as orange juice or colas enhances absorption temic fungal infections. (need low pH). A new IV formulation has also been developed to avoid poor absorption. Ketoconazole Ketoconazole, one of the imidazoles, is the drug of Voriconazole choice for chronic mucocutaneous candidiasis ( Can- dida on every surface). It is NOT used for systemic Voriconazole has a Voracious appetite for fungi!!! candidiasis (amphotericin B, remember?). Ketocona- Voriconazole is a promising triazole antifungal. Al- zole is currently not used for the treatment of systemic though more clinical experience is needed, data are suf- fungal infections. The safer, more efficacious, oral itra- ficient to support its future use in patients with invasive conazole and old faithful, amphotericin B, are the first aspergillosis who have failed to respond to agents of line drugs. choice (i.e. conventional or liposomal amphotericin B, itraconazole). Adverse Effects 1) GI: Nausea, vomiting, and anorexia, all common. 2) Hepatotoxicity: This is usually seen as a tempo- Other Antifungal Drugs rary rise of hepatic enzymes but on rare occasions can lead tohepatic necrosis. Follow enzymes when on this drug. Nystatin 3) Inhibition of testosterone synthesis: Keto- conazole inhibits the cytochrome P-450 system, which is Nystatin, like amphotericin B, binds to ergosterol, in- important in testosterone synthesis. The result is gy- creasing the permeability of the cell membrane and necomastia, impotence, decreased sex drive (libido), and causing cell lysis. decreased sperm production. Think "Nasty Nystatin" because this drug is too 4) Adrenal suppression. toxic to take parenterally (intravenously). It is only

157 CHAPTER 21. ANTIFUNGAL ANTIBIOTICS

Figure 21-2 used topically on the skin and mucous membranes. Griseofulvin Also, since it is not absorbed from the gastrointestinal tract, oral nystatin can be used to treat oral and Fig. 21-3. Visualize griseofulvin as a greasy ful esophageal infections with yeast or fungi. You will or- cram used to lever the dermatophyte plaques off the der nystatin on the wards as Nystatin, Swish and skin. It inhibits fungal growth by disrupting spindle for Swallow for treatment of oral, esophageal, and gas- mation, thus preventing mitosis. Note the worker peel tric candidiasis. It is also given topically for vaginal ing fungus off your "toe,"sis. candidiasis. Griseofulvin deposits in keratin precursor cells in the skin, hair, and nails, where it inhibits the growth Fig. 21-2. Nasty Nystatin cruises down the esopha- of fungi in those cells. Note that it does not kill the gus killing fungi on the wall of the esophagus. In one fungi; it just inhibits their growth (static rather than end and out the other! cidal). The uninfected drug-infiltrated keratin precur

158 CHAPTER 21. ANTIFUNGAL ANTIBIOTICS

sor cells mature and move outward toward the kera- synthesis by inhibiting the formation of squalene epox- tinized layer. As the older, infected cells fall off with ide from squalene. Terbinafine tends to accumulate normal cell turnover, this translates into a slow cure i n nails, and is therefore useful for tinea unguium of skin fungus. (onychomycosis). It also appears useful in the treat- Adverse effects of griseofulvin are uncommon. They ment of tinea pedis, tinea capitis, and tinea corporis. include headache, nausea, vomiting, photosensitivity, Since it is not metabolized by the cytochrome p450 sys- and mental confusion, in addition to bone marrow sup- tem (as do the azole antifungals), there is little poten- pression (leukopenia and neutropenia). tial for drug-drug interactions.

Potassium Iodide Reference

Potassium iodide is used to treat sporotrichosis. Re- Bennett JE. Antifungal Agents. In: Mandell GL. Bennett JE, member that you get sporotrichosis from pricking your Dolin R, eds. Principles and Practice of Infectious Diseases. finger in the garden. "You get Sporotrichosis while Pot- 4th edition. New York: Churchill Livingstone 1995; ting plants." If the infection becomes systemic, ampho- 401-410. tericin B or itraconazole is better. Jackson CA, et al. Drug therapy: Oral azole drugs as systemic antifungal therapy. N Engl J Med 1994;330:263-272. Fig. 21-4. Summary of the anti-fungal drugs. Sanford JP, Gilbert DN, et al. Guide to antimicrobial therapy 1994. Antimicrobial Therapy, m c, Dallas Texas; 1994. Terbinafine Recommended Review Articles: Terbinafine is a new oral fungicidal agent that blocks fungal cell wall synthesis. It blocks ergosterol Terrell CL. Antifungal agents. Mayo Clin Proc 1999:74:78-100.

Figure 21-3

159 Figure 21-4 ANTI-FUNGAL DRUGS M. Gladwin and B. Trattler. Clinical Microbiology Made Ridiculously Simple WedMester PART 3. VIRUSES

Chapter 22. VIRAL REPLICATION and TAXONOMY

Viruses have these unique characteristics:

1) They are energy-less. They float around until they come in contact with an appropriate cell. 2) They are basic life forms composed of a protein coat, called a capid, that surrounds genetic material. Viruses do not have organelles or ribosomes. Certain viruses are further enclosed by an external lipid bilayer membrane that surrounds the capsid and may contain glycoproteins. Some viruses also carry some structural proteins and enzymes inside their capsid. 3) The genetic material is eihe DNA o RNA. Nee boh!! The genetic material contains instruc- tions to make millions of clones of the original virus. 4) Replication of the genetic material occurs when the virus takes control of the host cells synthetic machinery. Viruses contain all of the genetic information, but not the enzymes, needed to build millions of replicas of the original virus.

VIRAL MORPHOLOGY

They say we learn best by doing, so lets study viral structure by making a virus, starting from the ncleic acid inside and proceeding to the capid and enelope.

Nucleic Acid Fig. 22-2. Viruses are classified as either DNA or RNA viruses. So we have two choices for our virus: DNA or RNA. Of course nothing is quite that simple. The nucleic acid strands can be single-stranded, double- stranded, linear, or looped, in separate segments or one continuous strand. The nucleic acid sequences can en- Figure 22-1 code a simple message or encode hundreds of enzymes and structural proteins. Fig. 22-1. Imagine that a virus is a specially designed military spaceship with a super-resistant outer shell. RNA Viruses However, the engineers forgot to build a fuel tank for their spaceship. It must therefore drift around until it Let us choose RNA for the core of our virus. There are encounters a satisfactory planet. When it lands, it 3 types of RNA for our virus: positive (+) stranded, neg- transfers the military cargo off the ship. This cargo is ative (-) stranded, or the RNA of the retroviruses. designed to take control of all factories and then instruct The POSITIVE (+) means that the RNA is JUST the factories to begin building copies of the original LIKE a messenger RNA (mRNA). When a positive (+) spacecraft (without fuel tanks). When the replica ships stranded RNA virus enters a host cell, its RNA can im- have been constructed, they will depart in mass, leaving mediately be translated by the hosts ribosomes into the planet in complete ruins. protein.

161 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

pendent RNA polymerase, so negative (-) stranded viruses must carry their own. Fig. 22-3. Translation of positive (+) and negative (-) RNA viruses. One special RNA virus deserves mention here: Retroviruses, of which the HN virus is a member. Fig. 22-4. The RNA of the retroviruses is transcribed in a reverse fashion ("retrograde") into DNA! To do this, these viruses carry a unique enzyme called reverse transcriptase.

DNA Viruses Fig. 22-5. Unlike RNA, DNA cannot be translated directly into proteins. It must first be transcribed into mRNA, with subsequent translation of the mRNA into Figure 22-2 structural proteins and enzymes. Every DNA virus has both a negative (-) strand and When negative (-) stranded RNA viruses enter a cell, a positive (+) strand. Here is the confusing part: The they are not able to begin translation immediately. positive (+) strand refers to the strand that is read, They must first be transcribed into a positive (+) strand while the negative (-) strand is ignored. of RNA (like mRNA). To do this, negative (-) stranded RNA viruses must carry, in their capsid, an enzyme Fig. 22-6. Unlike positive (+) stranded RNA, which is called RNA-dependent RNA polymerase, which will translated directly into proteins, the positive (+) carry out the transcription of the negative (-) strand stranded DNA is used as a template for transcription into positive (+). Human cells do not have an RNA-de- into mRNA.

Figure 22-4

162 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

Figure 22-5

Figure 22-6

Capsids Now that we know about the different types of nucleic acids, lets build a structure to house the genome. First we will build a capsid. There are two types of capsids: Icosahedral and helical.

Icoahedal Smme Capid

Figure 22-8

Figure 22-7

Fig. 22-7. Take 1 or more polypeptide chains and organize them into a globular protein subunit. This will be the building block of our structure and is called a capome.

Fig. 22-5. Arrange the capsomers into an equilateral triangle.

Fig. 22-9. Place 20 triangles together to form an icosahedron.

Package the DNA or RNA inside the icosahedral capsid! Figure 22-9

163 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

Figure 22-10

Helical Symmetry Capsids

Fig. 22-10. In helical symmetry the protein capsomers are bound to RNA (always RNA because only RNA viruses have helical symmetry) and coiled into a helical nucleoprotein capsid. Most of these assume a spherical shape except for the rhabdoviruses (rabies virus), which have a bullet-shaped capsid.

Envelope

Fig. 22-11. Now that we have made an icosahedral capsid with a nucleic acid (RNA or DNA) inside and a coiled helical nucleocapsid (RNA), let us cover the structure with a lipid bilayer membrane. Viruses acquire this membrane by budding through the host cell nuclear or cytoplasmic membrane and tearing off a piece of the membrane as they leave There may be various glycoproteins embedded in their cell membranes.

Viruses that do not have membranes are referred to as naked or nonenveloped. Those with membranes are referred to as enveloped. Figure 22-11 Finished Product The appearance of the complete viruses Fig. 22-12. 2) Capsid: and their approximate sizes compared to the bacterium Icosahedral Chlamydia, Rick- E. coli, and the very small bacteria, Helical ettsia, and Mycoplasma pneumoniae. 3) Envelope: CLASSIFICATION Naked Enveloped Viruses are classified according to their: 4) Size: 1) Nucleic acid: The diameter of the helical capsid viruses Type of nucleic acid: DNA, RNA The number of capsomers in icosahedral capsids Double- vs. single-stranded Single or segmented pieces of nucleic acid Positive (+) or negative (-) stranded RNA We will now go over the virus families and the char- Complexity of genome acteristics that separate them.

164 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

Figure 22-12

165 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

DNA Viruses 3) Five have icosahedral symmetry: Reo, Picorn Toga, Flavi, Calici (Rhabdo has helical symmetry but These are sometimes referred to as the HHAPPPy shaped like a bullet). viruses: 4) Two undergo replication in the nucleus: Retro Herpes Orthomyxo. Hepadna Adeno Fig. 22-14. The RNA viruses. Papova Parvo Pox VIRAL REPLICATION Most DNA viruses are double-stranded, show icosa- Viruses cannot reproduce on their own. They must in- hedral symmetry, and replicate in the nucleus (where vade a cell, take over the cell's internal machinery and DNA customarily replicates). instruct the machinery to build enzymes and new viral Two DNA viruses break these rules: structural proteins. Then they copy the viral genetic material enough times so that a copy can be placed in 1) Parvoviridae: This virus is so simple that it only each newly constructed virus. Finally, they leave the has a single strand of DNA. It is as simple as playing a host cell. The invading virus also blocks the synthesis of ONE PAR hole in golf. any host DNA, RNA or proteins. This feature forces the 2) Poxviridae: This virus is at the opposite end of host cell to construct only viral proteins and copies of the spectrum and is extremely complex. Although it the viral genetic material. does have double-stranded DNA, the DNA is complex in In order for viruses to reproduce, they must complete nature, coding for hundreds of proteins. This virus does these 4 steps: not have icosahedral symmetry. The DNA is surrounded by complex structural proteins looking much 1) Adsorption and penetration. like a box ( POX IN A BOX). This virus replicates in the 2) Uncoating of the virus. cytoplasm. 3) Synthesis and assembly of viral products (as well as inhibition of the host cell's own DNA, RNA and pro- Three of the DNA viruses have envelopes: tein synthesis). Herpes Hepadna Pox 4) Release of virions from the host cell (either by ly- Three are naked: A woman must be naked for the sis or budding). PAP smear exam. PApova Adeno PArvo Adsorption and Penetration Fig. 22-13. The DNA viruses. Fig. 22-15. The viral particle finds to the host cell membrane. This is usually a specific interaction in which a viral encoded protein on the capsid or a glyco- RNA Viruses protein embedded in the virion envelope binds to a host There are certain generalities about RNA viruses, cell membrane receptor. Unlike the bacteriophage most of which are the opposite of DNA viruses. virion (see Chapter 3 on Bacterial Genetics), which in- Most RNA viruses are single-stranded (half are jects its DNA, these viruses are completely internalized, positive [+1 stranded, half negative [-1), enveloped, capsid and nucleic acid. This internalization occurs by show helical capsid symmetry, and replicate in the endocytosis or by fusion of the virion envelope with the cytoplasm: host cell membrane. Toga Orthomyxo Corona Paramyxo Uncoating Retro Rhabdo Picorna Bunya The nucleic acid is released from the capsid into the Calici Arena nucleus or cytoplasm. Reo Fibo

Exceptions: Transcription, Translation, Replication RNA Viruses 1) Reoviridae are double-stranded. 2) Three are nonenveloped: Picorna, Calici, and These viruses usually undergo transcription, transla- Reoviridae. tion, and replication in the cytoplasm.

166 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

167 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

Figre 22-15

Fig. 22-16. Positive (+) stranded RNA virus replication. These viruses do not carry an RNA dependent RNA Figure 22-16 polymerase because they are read by the host directly POSITIVE (+) as mRNA. STRANDED RNA VIRUS REPLICATION Fig. 22-17 Negative (-) stranded RNA virus replication. The virus uncoats, releases a virion associated RNA polymerase, and must first transcribe the negative ( -) strand to a positive (+) strand (using the RNA polymerase). The positive (+) strand then acts like mRNA and undergoes both transcription and translation.

DNA Virses Transcription and replication usually occur in the nucleus.

Fig. 22-18. DNA virus replication. DNA viruses tend to be more genetically complex than RNA viruses. Thus, viral transcription is divided into immediate early, early, and late transcription. Another important concept is that DNA viruses act in a similar fashion as our own genome. Segments of DNA are transcribed in the nucleus into mRNA, are spliced and processed, and the mRNA then moves to the cytoplasm (endoplasmic reticulum) where translation occurs. Immediate early and Early: The initially transcribed mRNA here encodes enzymes and proteins needed for DNA replication and for further transcription of late mRNA. Late: The mRNA is usually transcribed after viral Figure 22-17 NEGATIVE (- ) DNA replication has begun and is transcribed from STRANDED RNA VIRUS REPLICATION

168 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

Figure 22-18 DNA VIRUS REPLICATION progeny DNA. The capsid structural proteins are syn- Naked virions: The cell may lyse and release the thesized from the late mRNA genome. virions, or the virions may be released by reverse phagocytosis (exocytosis). Enveloped virions: The newly formed naked virion Assembly and Release acquires its new "clothing" by budding through the The structural proteins and genome (RNA or DNA) Golgi apparatus, nuclear membrane, or cytoplasmic assemble into the intact helical or icosahedral virion. membrane, tearing off a piece of host cell lipid bilayer as The virion is then released. it exits.

169 CHAPTER 22. VIRAL REPLICATION AND TAXONOMY

HOST CELL OUTCOME Latent infection: The virus can survive in a sleeping state, surviving but not producing clinically overt infec- Death: With the viral infection, the host cell's own tion. Various factors can result in viral reactivation. function shuts down as the cell is commandeered for Chronic slow infection: Some viruses will cause virion replication. This can result in cell death. disease only after many years, often decades, of indolent Transformation: Infection can activate or introduce infection. oncogenes. This results in uncontrolled and uninhibited cell growth. Fig. 22-19. Summary of virus morphology.

170 •Note: Deity virus (causes hepatitis) is an incomplete RNA virus. It needs the coinfection with of hepatitis B virus to cause disease

L' O')1 Q VIR Ai . MORPHOLOGY M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaster CHAPTER 23. ORTHOMYXOVIRIDAE and PARAMYXOVIRIDAE

Figure 23-1

NUCLEOPROTEIN (NP) These 2 viral families have similar structures and the ability to adsorb to glycoprotein receptors, particularly in the upper respiratory tract. The orthomyxoviridae

are all influenza viruses, which cause the "ORdinary SEGMENTED RNA flu." Paramyxoviridae also replicate in the upper respiratory tract and can produce influenza-like illness, but they also produce a PARAde of distinctly different dis- Figure 23-2 eases. The paramyxoviridae include parainfluenza virus, mumps, measles, and respiratory syncytial virus. Fig. 23-1. The orthomyxoviridae and paramyxoviridae.

ORTHOMYXOVIRIDAE Understanding the structure of this virus will be important to you as a physician. The ability to produce epidemics and susceptibility to antibody immunity d vaccination all depend on the viral ultrastructure. You will see at the end of this section that the paramyxoviridae have a similar structure with a few small changes (making it oh so easy to learn!). Fig. 23-2. The orthomyxoviridae are spherical virions. At the virion center lie 8 segments of negative ( -) stranded RNA put together with a protein (nucleocapsid protein - NP) into a helical symmetry capsid. Surrounding the nucleocapsid lies an outer membrane studded with long glycoprotein spikes. There are 2 distinct types of glycoprotein: one with Hemagglutinin Activity (HA) and one with Neuraminidase Activity (NA). Anchoring the Figure 23-3 1 bases of each of these spikes on the inside of the viral lipid bilayer are membrane proteins ( M-proteins). viral genome into the host cell. So HA is needed for ad• Hemagglutinin (HA) sorption! Antibodies against HA will block this binding and prevent infection. Fig. 23-3. Hemagglutinin (HA) can attach to host sialic acid receptors. Sialic acid receptors are present on Neuraminidase (NA) the surface of erythrocytes, so viruses with HA glycoproteins cause heme-agglutination when mixed with Neuraminic acid is an important component of mucin, red blood cells. the substance covering mucosal epithelial cells and Host cell sialic acid receptors also exist on upper res- forming an integral part of the host's upper respiratory piratory tract cell membranes, and HA binding to these defense barrier. As the name implies, neuraminidase receptors activates fusion of the host cell membrane (NA) cleaves neuraminic acid and disrupts the mucin with the virion membrane, resulting in dumping of the barrier, exposing the sialic acid binding sites beneath.

172 I CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE Fig. 23-4. Viral NA and HA act as tag team wrestling with fever, chills, myalgias, arthralgias, headache, and partners, wrestling down the hosts defenses. NA other miseries? cleaves the cell mucin barrier, while HA fuses to the A: Antigenic Drift: During viral replication muta- cells sialic acid residues, enabling viral adsorption and tions can occur in the HA or NA, leading to changes in penetration. the antigenic nature of these glycoproteins. This is termed antigenic drift because the changes are small, Again, antibodies directed against NA are also just a little drift of the sailboat in the water. The re- protective. sulting new strains are only partially attacked by our immune system, resulting in milder disease in adults Influenza Serology and Epidemiology who have previously acquired antibodies. Major muta- tional changes usually result in altered codon reading There are 3 types of influenza virus: A, B, and C. frames and a nonviable virus. These types have many strains separated by antigenic differences in HA and NA. Type A infects humans, other Q: We all think that this is a pesky but mild self-lim- mammals (swine, etc.), and birds. Type B and C have iting disease. It can cause pneumonia and more serious only been isolated from humans. disease in the elderly, but usually it resolves without When looking at the disease influenza, 2 questions complications in 3 to 7 days. So why have there been about epidemiology arise: devastating pandemics of influenza throughout history, as in 1918? Over a few weeks in 1918, 548,452 per- Q: If antibody to the NA and HA are protective, why sons in the U. S., 12.5 million persons in India, and 20 do we continually get epidemics of the bothersome flu, million persons worldwide died from this virus.

Figure 23-4

173 CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE

A: Antigenic Shift: Now we are really shifting In 1997, a new strain of avian influenza (Influenza A, gears. We are taking the boat mentioned above and H5N1) was transmitted from infected poultry to humans airlifting it to a mountain in the Himalayas. With anti- in Hong Kong. This avian flu virus contained super- genic shift there is a complete change of the HA, NA, charged HA similar to that in the 1918 pandemic that or both. This can only occur with influenza type A killed over 20 million people. The supercharged HA en- because the mechanism involves the trading of RNA abled the virus to kill almost half of the people who became segments between animal and human strains. When 2 infected. Fortunately, the virus was poorly transmissible i nfluenza types co-infect the same cell, undergo replica- to humans, and was controlled by destroying the poultry tion and capsid packaging, RNA segments can be mis- in Hong Kong. This was certainly a close call. packaged into another virus. This virus now wields a new HA or NA glycoprotein that has never been exposed Complications of Influenza to a human immune system anywhere on the planet. So the entire human population would be susceptible, lead- Even the normal yearly flu can cause complica- ing to devastating pandemics. tions. The elderly and immunocompromised suffer The new HA and NA antigens are given number sub- more serious illness as the virus spreads to the lower scripts to differentiate them. The pandemic of 1889 respiratory tract, resulting in pneumonia. The viral was caused by a virus with an H2 hemagglutinin, the infection also lowers the host defenses against pandemic of 1900 was caused by a new virus with H3 many bacteria. Secondary bacterial pneumonias by hemagglutinin; in 1918 a swine flu virus transferred Staphylococcus aureus, Streptococcus pneumoniae, its HA to a human virus and so was called Hswine and others are common and the physician must follow hemagglutinin (HSW). The chart below is only in- patients (especially the elderly) closely until complete cluded to demonstrate the many pandemics and their resolution of their illness. New fevers or failure to im- new HA and NA antigenic composition. prove means danger!! Global pandemics: Fig. 23-6. Study the figure of the child with the crown 1989: H2N2 (the Rey- Spanish for king) and the lightning bolts 1900: H3N2 around his head and liver. Children given aspirin when 1918: H1N1: "Spanish flu"-highly pathogenic they have influenza or varicella (chicken pox) can de- strain-with high mortality (estimated velop a severe liver and brain disease called Reyes 20-40 million deaths worldwide) Syndrome. It is not yet known why this occurs. Give 1947: H1N1 acetaminophen for fever in children, no aspirin!!!! 1957: H2N2 "Asian flu"-illness but low mortality Diagnostic tests for influenza fall into 4 broad 1968: H3N2 "Hong Kong flu"-illness but low categories: mortality 1977: H1N1 1. Virus isolation: Culture of the virus allows for genetic and antigenic analysis " Notice also that some strains caused a second pan- 2. Detection of viral proteins: New one hour tests help demic as a new unexposed population grows to adulthood. guide the choice of antiviral agents Fig. 23-5. Antigenic drift and shift: For influenza epi- 3. Detection of viral nucleic acid (RNA) in clinical demics and pandemics to occur in people other than material is available by reverse transcription fol- children (who do not yet have antibodies), the antigens lowed by PCR (very sensitive method) in the NA and HA must somehow change, through 4. Serological diagnosis: 4-fold increase in specific antigenic drift and antigenic shift. antibody levels over 2 weeks

Figure 23-5

174 CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE

mumps virus, and measles virus. Before reading about each, lets examine the big picture:

1) Think lungs: All adsorb to and replicate in the upper respiratory tract. Respiratory syncytial virus and parainfluenza virus both cause lower respiratory infections (pneumonia) in children and upper respiratory tract infections (bad colds) in adults. 2) Think kids: Most infections occur in children. 3) Think viremia: The viral infection results in dissemination of virions in the blood to distant sites. Mumps and measles reproduce in the upper respiratory tract and spread hematogenously to distant organs. Mumps can produce local parotid and testes infection (parotitis and orchitis), and measles can produce a severe systemic febrile illness. Brain infection (encephalitis) can occur with both mumps and measles.

Figure 23-6 Parainfluenza Virus

The parainfluenza virus causes upper respiratory infection in adults ranging from cold symptoms such as Treatment and Control rhinitis, pharyngitis, and sinus congestion, to bronchi- Influenza viruses are grown in mass quantities in tis and flu-like illness. Children, elderly, and the im- chick embryos, which are then inactivated, purified, and munocompromised also suffer from lower respiratory used as vaccines. Scientists carefully choose 3 strains tract infections (pneumonia). that are circulating in the population or expected to cause Croup is a parainfluenza infection of the larynx and an outbreak in the next season. These vaccines have vari- other upper respiratory structures (laryngotracheo- able success depending on the accuracy of the "guess- bronchitis) that occurs in children. Swelling of these work." The vaccines should be given to the elderly, structures produces airway narrowing. Stridor (a immunocompromised patients, and health-care workers. 1 wheezing sound) and a barking cough (like a seal) occur There are now a few choices for treating the flu. as air moves through the narrowed upper airways. Amantadine and rimantidine prevent the uncoating of influenza A. They can both prevent influenza A Respiratory Syncytial Virus (RSV) infection and can reduce the severity of symptoms. Sanamavir (inhaled) and oseltamivir (oral) are neu- RSV is so-named because it causes respiratory infec- raminidase (NA) inhibitors, which can shorten the tions and contains an F-protein that causes formation of course of influenza A and B. multinucleated giant cells (syncytial cells). This virus differs from the rest of its kin by lacking both the HA and NA glycoproteins. PARAMYXOVIRIDAE RSV is the number one cause of pneumonia in young children, especially in infants less than 6 months of age. The structure of paramyxoviridae is very similar to The virus is highly contagious with outbreaks occurring that of the orthomyxoviridae. The differences are that: in winter and spring. The treatment of RSV infection 1) The negative (-) stranded RNA is in a single is less than ideal, with ribavirin studies showing con- strand, not segmented. flicting results. Efforts have therefore focused on pre- 2) HA and NA are a part of the same glycoprotein vention. RSV infection can be prevented in a high spike, not 2 different spikes. percentage of cases with palivizumab, which is a 3) They possess a fusion (F) protein (not present in monoclonal antibody against RSV that is produced by a the orthomyxoviridae) that causes the infected host recombinant DNA method. A blood-derived product, cells to fuse together into multinucleated giant cells serum RSV immune globulin, is also available, but (syncytial cells similar to those caused by herpesviridae comes with the risk of transmission of blood-borne and retroviridae infection). infections. Previously infected persons are not entirely immune, There are 4 paramyxoviridae that cause human dis- but the subsequent infections are usually limited to the ease: parainfluenza virus, respiratory syncytial virus, upper respiratory tract.

175 CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE

Mumps Virus Mumps virus replicates in the upper respiratory tract and in regional lymph nodes and spreads via the blood to distant organs. Infection can occur in many organs, but the most frequently involved is the parotid gland.

Fig. 23-7. About 3 weeks after initial exposure to mumps virus the parotid gland swells and becomes painful. The testes are also frequently infected. About 25% of infected males who have reached puberty can de velop orchitis. The testes enlarge and stretch the capsule, resulting in intense pain. Infertility is a rare complication. Meningitis and encephalitis can also occur, the former being more common and less severe.

There is only one antigenic type, and a live attenuated viral vaccine is a part of the trivalent measles- mumps-rubella (MMR) vaccine. Measles Virus Due to the effectiveness of the MMR vaccine, there were only 2,900 cases of measles in the U. S. in 1988. However, the disease continues to have worldwide impact with about 2 million deaths annually.

Fig. 23-8. The clinical manifestations of measles (also Figure 23-7 called rubeola).

Exposure \ Measles virus is highly contagious and spreads through nasopharyngeal secretions by air or by

Figure 23-8

176 CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE

Figure 23-9

Figure 23-10

direct contact. The virus multiplies in the respira- Kopliks Spots tory mucous membranes and in the conjunctival membranes. Incubation lasts for 2 weeks prior to the Fig. 23-10. Kopliks spots. A day or 2 before the rash, development of rash. the patient develops small red-based lesions with blue- white centers in the mouth. Think of a cop licking a red- Prodrome white-blue lollipop.

Fig. 23-9. Measles prodrome. Prior to the appearance Rash of the rash, the patient suffers from prodromal illness with conjunctivitis, swelling of the eyelids, photophobia, The measles rash is red, flat to slightly bumpy (mac- high fevers to 105 F, hacking cough, rhinitis, and ulopapular). It spreads out from the forehead to the face, malaise (feels cruddy). neck, and torso, and hits the feet by the third day.

177 CHAPTER 23. ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE

Figure 23-11

Fig. 23-11. As the measles rash spreads downward, Subacute sclerosing panencephalitis (SSPE) is a the initial rash on the head and shoulders coalesces. slow form of encephalitis caused by measles virus. Many The rash disappears in the same sequence as it devel- years after a measles infection the child or adolescent oped. Visualize a can of measles-brand red paint be- may have slowly progressing central nervous system ing poured over a patient's head. The paint is thicker disease, with mental deterioration and incoordination. over the head and shoulders and drips completely off The MMR vaccine, which contains live attenuated in 6 days. measles virus, is preventative.

Complications Fig. 23-12. Summary of the orthomyxoviridae and paramyxoviridae. Like mumps, the measles virus disseminates to many organ systems and can damage those sites, causing pneumonia, eye damage, heart involvement (myocarditis), and Recommended Review Articles: the most feared complication, encephalitis. Encephalitis Cox NJ, Subbarao K Influenza. The Lancet is rare, but 10% of patients who develop this will die. 1999;354:1277-1281. Domachowske J, Rosenberg H. Respiratory Syncytial Virus Infection with measles during pregnancy does not Infection: Immune Response, Immunopathogenesis, and cause birth defects but has been associated with spon- Treatment. Clinical Microbiology Reviews April 10, 1999; taneous abortion and premature delivery. In fact, 298-309. measles in pregnant women results in fetal death in Steinhauer D. Role of Hemagglutinin Cleavage for the Patho- 20% of cases. genicity of Influenza Virus. Virology 1999; 258: 1-20.

178 Figure 23-12 ORTHOMYXOVIRIDAE AND PARAMYXOVIRIDAE M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple OMedMaster CHAPTER 24. HEPATITIS VIRIDAE

Viral hepatitis is an infection of the liver hepatocytes by The details of how to determine which virus is caus- viruses. There are 5 known viruses that infect the liver. ing the hepatitis will be discussed with each virus. 2) Chronic viral hepatitis is more difficult to diag- The 5 RNA viruses are: nose because the patient is often asymptomatic with only an enlarged tender liver and mildly elevated liver. 1) Hepatitis A virus (HAV). function enzyme levels. 2) Hepatitis C virus (HCV), which was previously called NON-A NON-B until it was isolated. 3) Hepatitis D virus (HDV). The Pattern of Liver Enzyme Elevation 4) Hepatitis E virus (HEV). Different diseases result in different patterns of liver. 5) Hepatitis G virus. function enzyme elevation. For example, viral hepatitis usually causes the transaminases ALT and AST to ele- There is 1 DNA virus called: vate to very high levels, while GGT, alkaline phosphatase, and bilirubin are only mildly elevated. As the 1) Hepatitis B virus (HBV) disease progresses, bilirubin levels rise higher. A gall- Hepatitis A and E are both transmitted via the fecal- stone in the bile duct causes the opposite to occur: biliru- oral route, while the rest are transmitted via blood-to- bin, alkaline phosphatase, and GGT rise higher than blood (parenteral) contact. Just as A and E are at both ALT and AST. The reason for this is a fellows. ends of ABCDE, so they are transmitted by elements of Fig. 24-1. The hepatocytes produce AST and ALT. both ends of the GI tract. A = Anal, E = Enteric, The cells that line the bile canaliculi produce alka- BCD = BlooD. line phosphatase and GGT. The bile canaliculi carry We will now discuss the clinical disease hepatitis and bilirubin. then cover each virus in more detail. Fig. 24-2. With viral hepatitis there is cell necrosis as VIRAL HEPATITIS the virus takes over the cell machinery. The hepatocytes rupture, resulting in the release of AST and ALT. Some Viral hepatitis can be a sudden illness with a mild to pericanalicular cells will also be destroyed. So we will severe course followed by complete resolution. This is see very high AST and ALT with a little elevation of al- called acute viral hepatitis and can be caused by all kaline phosphatase and GGT. As the infection worsens, of these viruses. Hepatitis can also have a prolonged the liver swells and the canaliculi narrow, resulting in course of active disease or silent asymptomatic infection a backup of bilirubin into the blood. So with viral he- termed chronic viral hepatitis. The parenterally patitis the ALT and AST are very high, and the biliru- (blood-to-blood) transmitted HBV, HCV, and HDV can bin, alkaline phosphatase, and GGT rise later in the cause chronic hepatitis. course. 1) Acute viral hepatitis has a variable incubation Fig. 24-3. A stone blocking the bile duct would re- period, depending on the virus type. The growth of the sult in: virus first results in systemic symptoms much like the 1) Inability to excrete the bilirubin, resulting in high flu, with fatigue, low-grade fever, muscle/joint aches, blood levels of bilirubin. cough, runny nose, and pharyngitis. One to two weeks 2) The backup results in increased alkaline phos- later the patient may develop jaundice as the level of phatase and GGT synthesis by the canalicular cells. bilirubin, which is normally cleared by the liver, rises. Imagine the backup of pressure popping the cells, re- As the virus grows in the hepatocytes, these liver cells sulting in the release of alkaline phosphatase and GGT necrose (die). The hepatocytes produce enzymes that are (not the true mechanism but a good memory tool). released during cell death. These are the liver-function enzymes aspartate aminotransferase (AST), alanine So with an obstructive process (stone in bile duct), AST aminotransferase (ALT), gamma-glutamyl transpepti- and ALT would only be minimally elevated; alkaline dase (GGT), and alkaline phosphatase. Elevated blood phosphatase, GGT, and bilirubin would be very elevated. levels of these liver enzymes help establish the diagnosis of hepatitis. Hepatitis A Virus (HAV) So about 2 weeks into the illness, the patient is often jaundiced, has a painful enlarged liver and high blood HAV has a naked icosahedral capsid with a posi- levels of liver-function enzymes. tive (+) single-stranded RNA nucleic acid. It is in the

180 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-1 family Picornaviridae, and as is the case with most of breaks often occur secondary to fecal-to-hand-to-mouth this family it is transmitted by the fecal-to-oral route contact. Examples of this include an infected food han- (HAV = Anus). dler contaminating food after poor hand washing, persons ingesting fecally contaminated drinking water, or Epidemiology close person-to-person contact in institutions such as day care centers. There is a 15-40 day incubation period HAVe you washed your hands??? About 25,000 cases (about 1 month) before the patient develops acute he- of hepatitis A infection are reported each year in the patitis as described earlier. U.S., and there are many more infections that are Young children are the most frequently infected, and asymptomatic or unreported. In fact, 40% of Americans they have a milder course than do adults, often without living in urban centers have serologic evidence of prior developing jaundice or even symptoms. At the other end infection, but only 5% remember the infection. Out- of the spectrum, a small percentage (1-4%), usually

181 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-2 adults, will develop fulminant (severe) hepatitis. How- lin will prevent or decrease the severity of infection, if ever, death from HAV is very rare (1%). given early during incubation. Pooled immune serum globulin is obtained by ethanol fractionation from the Serology plasma of hundreds of donors. Since anti-HAV IgG is present in about 40% of the population, there will be an- Serologic tests can help establish the diagnosis. The tibody in the pooled immune serum globulin that will in- HAV capsid is antigenic, resulting in the host produc- activate the virus. Once infection is established, tion of anti-HAV IgM and later, the anti-HAV IgG. A pa- treatment is only supportive. tient with active infection will have anti-HAV IgM detectable in the serum. Anti-HAV IgG indicates old infection and no active disease. This antibody lasts indef- Hepatitis B Virus (HBV) initely and is protective, which means that it will protect against future infection with HAV. You will have an intimate relationship with HBV throughout your career. Why is this? In an infected pa- Fig. 24-4. Hepatitis A infection: A time line of clinical tient, this virus lives in all human body fluids (semen, symptoms and antibody development. urine, saliva, blood, breast milk. .. ). As a physician, Fig. 24-5. Hepatitis A serology. you will come into contact with patients who harbor this virus. Since hospital workers are considered to be an at- Treatment risk group, you will receive immunization against HBV. So you will touch this virus frequently and will actually A new vaccine is available and may be given to peo- harbor antibodies against it. ple at high risk of HAV infection, such as travelers. If a person has been exposed, pooled immune serum globu- HBV = Big and Bad

182 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-3

Figure 24-4

183 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-5 SEROLOGY OF HEPATITIS A

HBV is very different from HAV. It is a Big (42 NM) der electron microscopy. Notice that the Dane particle virus with an enveloped icosahedral capsid and double- has an envelope and an icosahedral capsid studded with stranded circular DNA. protein spikes. In its core is a double-stranded DNA with associated DNA polymerase enzyme. Fig. 24-6. The intact virus is called the Dane parti- When looking at infected blood with electron mi- cle ( Big like a Great Dane) and looks like a sphere un- croscopy, you will notice the Dane particle spheres, de•

Figure 24-6

184 CHAPTER 24. HEPATITIS VIRIDAE

scribed above, as well as longer filamentous structures. c) Chronic active hepatitis: The patient has an These filamentous structures (as seen under electron acute hepatitis state that continues without the nor- microscopy) are composed of the envelope and some cap- mal recovery (lasts longer than 6-12 months). sid proteins that have disassociated from the intact 4) Co-infection with hepatitis delta virus virion. This part of the virus is called the hepatitis (HDV): See HDV section. B surface antigen (HBsAg) and is of critical importance because antibodies against this component (anti- Liver injury appears to occur from a cell-mediated im- HBsAg) are protective. Having anti-HBsAg means the mune system attack on HBV. Viral antigens on the sur- patient is immune against HBV. face of infected hepatocytes are targets for cytotoxic Removing HBsAg leaves the viral core, which is T-cells. Immune complexes of antibody and HBsAg can called hepatitis B core antigen (HBcAg) and is also deposit in tissues and activate the immune system, re- (anti- antigenic. However, antibodies against the core sulting in arthritis, as well as skin and kidney damage. HBcAg) are not protective (do not result in immunity). Patients who have immunosuppressed states, such as During active infection and viral growth, a soluble malnutrition, AIDS, and chronic illness, are more likely component of the core is released. This is called HBeAg. to be asymptomatic carriers because their immune sys- This antigen is a cleavage product of the viral core struc- tem does not attack. tural polypeptide. HBeAg is found dissolved in the serum, and is a marker for active disease and a highly infectious state. Pregnant mothers with Complications HBeAg in their blood will almost always transmit HBV to their offspring (90% transmission rate), whereas Primary hepatocellular carcinoma is a compli- mothers who have no HBeAg will rarely infect the cation of HBV. With chronic infection the HBV DNA neonate (10% transmission rate). becomes incorporated into the hepatocyte DNA and triggers malignant growth. There is a 200X increase in the risk of developing primary hepatocellular carcinoma Epidemiology in HBV carriers as compared to noncarriers. Infection with HBV can result in permanent liver scar- HBV is present in human body fluids and is transmit- ring and loss of hepatocytes. This is called cirrhosis. ted from blood-to-blood contact. This non-oral transmission is called parenteral transmission. Transmission from an infected patient can occur by needle sharing, ac- Serology cidental medical exposures (needle sticks, blood spray, touching blood with unprotected hands), sexual contact, Serologic tests help establish HBV infection. The blood transfusions, perinatal transmission, etc. This many antigens and antibodies are simpler than they virus is extremely contagious. seem, as follows:

1) HBsAg: The presence of HBsAg always means Pathogenesis there is LIVE virus and infection, either acute, chronic, or carrier. When anti-HBsAg develops, HBsAg disap- Another reason that HBV is a Bad dude is that pears and the patient is protected and immune. unlike hepatitis A, which can only cause an acute a) HBsAg = DISEASE (chronic or acute) hepatitis, HBV can cause acute and chronic hepati- b) Anti-HBsAg = IMMUNE, CURE, NO AC- tis. The following are disease states caused by BIG TIVE DISEASE!!! BAD HBV: 2) HBcAg: Antibodies to HBcAg are not protective but we can use them to understand how long the infec- 1) Acute hepatitis. tion has been ongoing. With acute illness we will see 2) Fulminant hepatitis: Severe acute hepatitis IgM anti-HBcAg. With chronic or resolving infection with rapid destruction of the liver. IgG anti-HBcAg will develop. 3) Chronic hepatitis: a) IgM anti-HBcAg = NEW INFECTION a) Asymptomatic carrier: The carrier patient b) IgG anti-HBcAg = OLD INFECTION never develops antibodies against HBsAg (anti- 3) HBeAg: The presence of HBeAg connotes a high HBsAg) and harbors the virus without liver injury. infectivity and active disease. Presence of anti-HBeAg There are an estimated 200 million carriers of HBV suggests lower infectivity. in the world. a) HBeAg = HIGH INFECTIVITY, virus go- b) Chronic-persistent hepatitis: The patient ing wild! has a low-grade "smoldering" hepatitis. b) anti-HBeAg = LOW INFECTIVITY

185 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-7 Fig. 24-7. Time course of acute HBV infection, with complete resolution and immunity.

Figure 24-8 Fig. 24-8. Time course of chronic HBV infection, with failure to develop the protective anti-HBsAg antibodies.

Treatment vaccine. There is no risk of developing disease from the Prevention and control of hepatitis B involves: vaccine because it contains only the surface envelope and proteins (HBsAg = no DNA or capsid). The HBV vaccine 1) Serologic tests on donor blood to remove HBV- is now given to all infants at birth, 2, 4, and 15 months; it contaminated blood from the donor pool. is also given as 3 injections to adolescents and high-risk 2) Active immunization: The vaccine is a recombinant adults (health care workers, IV drug users, etc.). vaccine. The gene coding for HBsAg is cloned in yeast and 3) Anti-viral agents for treatment of chronic active or used to produce mass quantities of HBsAg, used as the persistent HBV infection:

186 CHAPTER 24. HEPATITIS VIRIDAE

Figure 24-9

Fig. 24-9. Serology of the medical student vaccinated with HBV recombinant vaccine.

Figure 24-10 SEROLOGY OF HEPATITIS B

Fig. 24-10. Hepatitis B serology.

a) The anti-HIV drug lamivudine suppresses HBV DNA to undetectable levels, but most patients have relapses when the drug is discontinued. (Dien- stag, 1995). b) Treatment with interferon alpha suppressed HBV DNA and HBeAg in 50% of treated patients and appears to prevent cirrhosis in these respon- ders (Niederau, 1996). New trials of combination therapy with interferon alpha and ribavirin are planned for patients with chronic active hepatitis B or C.

Hepatitis Delta Virus (HDV) This RNA virus is transmitted parenterally and Figure 24-11 can only replicate with the help of HBV. The delta virus helical nucleocapsid actually uses HBV's envelope, HBsAg. HDV steals the clothes from HBV and can only cause infection with the HBsAg coat. 1) Co-infection: HBV and HDV both are transmit- Fig. 24-11. Notice the HBV envelope and proteins ted together parenterally (IV drug use, blood transfu- surround the HDV helical nucleocapsid. Next to it is a sions, sexual contact, etc.) and cause an acute hepatitis conceptual figure of the letter D in a big B. similar to that caused by HBV. Antibodies to HBsAg will be protective against both, ending the HBV+ HDV= Big Bad Dude infection. 2) Superinfection: HDV infects a person who has Without Big Bad HBV, HDV is just a dud and is not chronic HBV infection (like the 200 million worldwide infectious. Infection occurs in 2 ways: HBV carriers). This results in acute hepatitis in a

187 CHAPTER 24. HEPATITIS VIRIDAE patient already chronically infected with HBV. This olution of liver inflammation (about 50% of treated pa- HDV infection is often severe, with a higher incidence of tients will respond). fulminant hepatitis, cirrhosis, and a greater mortality The problem is that treatment with interferon alpha (5-15%). The patient with chronic HBV cannot make makes patients feel like they have the flu, and only Anti-HBsAg and so remains chronically infected with 10-25% will have lasting remissions after therapy is both HBV and HDV. discontinued (Poynard, 1995). Treatment with the anti-viral drug ribavirin only 1 Serology is currently not very helpful for diagnostic temporarily normalized liver enzymes in /3 of patients purposes because IgM and IgG anti-HDV are in the (Di Bisceglie, 1995). serum for only a short period. As there is no treatment, control of HBV infection is currently the only way to pro- Hepatitis E Virus (HEV) tect against HDV. HEV hepatitis is often referred to as non-A hepatitis because it shares similarities with HAV. HEV is also Hepatitis C Virus (HCV) transferred by the fecal-oral route, frequently with the consumption of fecally contaminated water during mon- Blood products were first screened for the presence of soon flooding. The E stands for Enteric (fecal-oral). Itis HBV, and the incidence of post-transfusion hepatitis de- endemic to Asia, India, Africa, and Central America. clined. However, there was still a risk of developing non- A, non-B hepatitis. Recently an etiologic agent has been Hepatitis G Virus identified and called hepatitis C virus (HCV). Most of the cases (about 90%) of non-A, non-B hepatitis are Hepatitis G is an RNA virus in the Flavivirus family. caused by HCV. Blood products are now also screened It is transmissible by transfusion & parenteral routes. for HCV. It has not conclusively shown to cause liver disease. HCV is transmitted parenterally and has been iden- Fig. 24-12. Summary of hepatitis viruses. tified as an enveloped icosahedral RNA virus. It causes acute and chronic hepatitis in a similar manner as HBV. References In fact, HCV should be called hepatitis Cirrhosis virus because half of those infected develop chronic he- Dienstag JL, et al. A preliminary trial of lamivudine for patitis. A large percentage of these develop chronic ac- chronic hepatitis B infection. N Engl J Med 1995;333: tive hepatitis and eventual cirrhosis. Hepatocellular 1657-61. carcinoma can develop in patients with chronic active Di Bisceglie AM, et al. Ribavirin as therapy for chronic active HCV infection and cirrhosis. hepatitis C: a randomized, double-blind, placebo-controlled trial. Ann Int Med 1995;123:897-903. Anti-HCV antibodies develop months after exposure Niederau C, et al. Long-term follow-up of HBeAg-positive pa- and are used to screen donor blood products and aid in tients treated with interferon alpha for chronic hepatitis B. the diagnosis of HCV induced hepatitis. N Engl J Med 1996;334:1422-7. Persons who develop chronic active HCV infection Poynard T, Bedossa P, et al. A comparison of three inter- have a high likelihood of developing cirrhosis and liver feron alpha-2b regimens for the long term treatment failure. For patients with chronic active HCV, treat- of chronic non-A, non-B hepatitis. N Engl J Med 1995; ment with alpha-interferon can sometimes result in res- 332:1457-62. Figure 24-12 HEPATITIS VIRIDAE M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaster CHAPTER 25. RETROVIRIDAE, HIV, and AIDS

ONCOGENES

What Is Cancer? Normal cells have strict growth control. They divide an exact number of times with exact timing, depending where in the body they are located. When normal cells are grown on a plate of nutrient media, they form a single layer and stop dividing when they touch each other. This is called contact inhibition. Malignant cells lose contact inhibition and pile up in vitro. They become immortal, dividing continuously as long as there is nutrient supply. In the body this uncontrolled growth causes physical damage by local expansion, steals nutrients from other cells, produces abnormally Figure 25-1 high levels of hormones or other cell products, and can infiltrate areas where other cells grow (such as the bone marrow). The retroviridae are a large group of RNA viruses that infect animals and humans. How Do Oncogenes Cause Cancer? Fig. 25-1. There are 3 big concepts unique to the The normal cell has receptor proteins in the cell mem- retroviridae: RETRO, GROW, and BLOW. brane that regulate cell growth. Growth factors (mito. gems) bind to these receptors to regulate growth. 1) Retro: Most RNA viruses (negative- or positive- Examples of these receptors are the insulin receptor, stranded), enter the host cell and act as mRNA or are the Epidermal Growth Factor (EGF) receptor, and the transcribed into mRNA. The retroviridae are different. Platelet Derived Growth Factor (PDGF) receptor. Mito- They carry with them a unique enzyme called reverse gen stimulation of these receptors causes intracellular transcriptase. This enzyme is an RNA-dependent phosphorylation of tyrosine. Phosphotyrosine then acts DNA polymerase that converts the viral RNA into as an intracellular growth messenger. DNA. This viral DNA has unique "sticky" ends that allow it to integrate into the host's own DNA, as Fig. 25-2. The Rous sarcoma virus oncogene (src), en- do transposons. codes a transmembrane protein that also phosphory- 2) Grow: Retroviruses can cause cancer in the cells lates tyrosine, but at ten times the normal rate!!! they infect. Genes called oncogenes in humans and an- The erb-B oncogene that causes cancer in chickens en- imals can cause the malignant transformation of nor- codes a protein similar to the EGF receptor. Other onco- mal cells into cancer cells. Some retroviruses carry genes encode proteins that are similar to the PDGF and oncogenes in their genome. Inactive oncogenes in ani- insulin receptors! mals and humans are called proto-oncogenes. These are genetic time bombs waiting for activation, which Still other oncogenes encode proteins that act at can occur by carcinogen-induced DNA mutation or by the nuclear level to promote uncontrolled expression of retrovirus infection. growth genes. 3) Blow: Some retroviridae are cytotoxic to certain cells, blowing them up. The most notable is the human i mmunodeficiency virus (HIV) which destroys the T- Retroviridae and Oncogenes helper lymphocytes it infects. This ultimately results in devastating immunodeficiency. Because most of the retroviridae isolated to date cause either leukemia or sarcoma in their vertebrate In this chapter we will discuss: 1) oncogenes; 2) the hosts, they are sometimes called leukemia sarcoma human retroviridae, using HIV as a model for retroviri- viruses. Some retroviruses cause cancer directly dae structure and genetics; and 3) HIV infection and ( acute) by integrating an intact oncogene into the host 4) the Acquired Immunodeficiency Syndrome (AIDS) DNA. Others cause cancer indirectly (nonacute) by acti- caused by HIV. vating a host proto-oncogene.

190 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

Figure 25-2

Acute Transforming Viruses The oncogene gene sequence is so long that most acute transforming viruses have lost their own RNA Fig. 25-3. Some retroviridae, the acute transforming critical for viral replication. These viruses are called de- viruses, carry intact oncogenes within their viral fective acute transforming viruses and require a co- genome, which when integrated into the host DNA infecting virus to cause cancer. cause malignant transformation. This integration is The Rous sarcoma virus is the only known acute facilitated by the "sticky" ends and an enzyme called transforming virus that is non-defective. It has the full integrase. RNA genome needed for replication and also carries an accessory src oncogene. The acute transforming viruses were discovered in 1911 when Peyton Rous injected cell-free filtered material from a chicken tumor into another chicken. The Non-acute Transforming Viruses chicken subsequently developed tumor. The causative Fig. 25-4. Other retroviridae, the non-acute trans- agent is now known to be a retrovirus called the Rous forming viruses, activate host cell proto-oncogenes by sarcoma virus which possesses within its DNA an in- integrating viral DNA into a key regulatory area. These tact oncogene called src. When the Rous sarcoma virus viruses do not carry oncogenes and thus have room for infects a cell, it reverse transcribes its RNA into DNA. The DNA is integrated into the host's genome by inte- the full genome necessary for viral replication. grase. Once integrated the src gene is expressed, causing malignant transformation. HUMAN RETROVIRUSES

Where Do Viral Oncogenes Come From? By the mid-1970's, retroviruses had been discovered in many vertebrate species, including apes. The hy- Studies have shown that normal host DNA has se- pothesis that humans may also be infected with retro- quences that are homologous to viral oncogenes but are viruses led to a search that ultimately resulted in the still inactive (proto-oncogenes). These genes most likely isolation of a retrovirus from the cell lines and blood of are involved in cell growth regulation. Somehow, during patients with adult T-cell leukemia. This virus is called normal viral infection and integration, a mistake in human T-cell leukemia virus (HTLV-I). splicing occurs and a virus "captures" a proto-oncogene. HTLV-I has now been linked to a paralytic disease This proto-oncogene ultimately becomes activated in that occurs in the tropics (Caribbean islands) called the virus so the virus now carries an oncogene. tropical spastic paraparesis. HTLV-1 induced

191 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

Figure 25-3 leukemia has also been described in the Caribbean Investigators stimulated T-cell culture growth (T - and Japan. cells from patients infected with AIDS) with inter- A second human retrovirus was isolated from T-cells leukin-2 and were able to find RNA and DNA, of patients with a T-cell variant of hairy cell leukemia. suggesting a retroviral etiology. The virus, which This is called HTLV-II, but this virus has no known role was subsequently identified, was called the human in producing disease. immunodeficiency virus (lily). A second retrovirus, called HIV-2, causes a dis- In early 1980 a new epidemic was first noted that we ease similar to AIDS in western Africa. It is a dis- now call the Acquired Immunodeficiency Syn- tantly related virus with 40% sequence homology with drome (AIDS). Several factors suggested that this dis- HIV-1. ease was caused by a retrovirus: A virus that causes an AIDS-like disease in primates, 1) The infectious agent was present in filtered blood simian immunodeficiency virus (SIV), shares a close se- products, such as concentrated factor VIII given to quence homology with HIV-2. patients with hemophilia. This suggested a viral etiology, as something small would be necessary to pass the filters. 2) There was a delayed onset between exposure (sex- HN STRUCTURE ual or blood products) and the development of disease. The structure of the virion and genome is similar for This delayed onset had been observed in the other all of these retroviruses. We will focus on HIV, the cause known retroviral diseases. of the world's most feared current epidemic. HIV is at 3) Immunodeficiency occurs with other animal retro- the center of intensive research aimed at halting its dev- viruses, such as feline leukemia virus. Even HTLV-I can astating disease, AIDS. cause immunosuppression. 4) AIDS patients have destruction of the T-helper Fig. 25-5. Under the electron microscope, HIV ap- lymphocytes. The known human retroviruses HTLV-I pears as a spherical enveloped virion with a central and II were both T-cell tropic. cylindrical nucleocapsid.

192 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

F 25-4

To examine this structure fully, we will start from the HN G i mide and work outward: Fig. 25-6. The HIV genome (simplified). All retro- 1) At the virion core lie 2 identical SS RNA pieces viruses possess, in their RNA genome, two ending long (a dimer). Associated with these are nucleocapsid terminal repeat (LTR) sequences, as well as the gag (NC) proteins bound to the RNA and the 3 essen- gene, pol gene, and env gene. tial retroviral enzymes, protease, reverse transcriptase and integrase. 1) LTRs (long terminal repeat sequences) flank 2) Surrounding the RNA dimer lies the capsid shell the whole viral genome and serve 2 important functions. which has icosahedral symmetry. The proteins that con- a) Sticky ends: These are the sequences, recog- stitute this shell are called capsid proteins (CA). The nized by integrase, that are involved in insertion major capsid protein is p24; this can be measured in the into the host DNA. Transposons, mobile genetic ele- serum to detect early HIV infection. ments, have similar flanking DNA pieces. 3) The rest of the virus has the same structure b) Promotor/enhancer function: Once incorpo- described for the influenza virus (see Chapter 23). Pro- rated into the host DNA, proteins bind to the LTRs teins under the envelope are called matrix proteins. that can modify viral DNA transcription. These proteins serve to hold the glycoprotein spikes 2) gag (Group antigen) sequences code for the pro- that traverse the lipid bilayer membrane (envelope). teins inside the envelope: Nucleocapsid (NC), capsid (CA)- The surface glycoproteins are referred to as gp fol- called p24, and matrix (MA) proteins. Thus, gag codes for lowed by a number: gp 120, and gp 41. the virion's major structural proteins that are antigenic.

193 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

F 25-5 ( Figure adapted from Fauci-In: Harrisons, 1994; and Haseltine, 1991)

3) pol encodes the vital protease, integrase, and re- 1) tat encodes the viral TrAnsacTivator protein. verse transcriptase enzymes. The only way the retro- This protein binds to the viral genome and activates viridae maintain their current POL position in the race transcription (thus transactivates). This is a potent pro- to cause human disease is with these unique enzymes. moter of viral activity. Protease is a vital HIV enzyme that cleaves gag and pol 2) rev is another promoter that REVS up viral activ- proteins from their larger precursor molecules (post- ity. It achieves this by a unique mechanism: translational modification). The HIV virus has multiple reading frames, produc- Protease deficient HIV virions can not form their vi- ing different mRNAs depending on where splicing oc- ral core and are non-infectious. New drugs have been curs. It can be spliced into many pieces, producing the developed that block the action of the HIV enzyme, pro- regulatory proteins such as tat, rev, nef(and others: uif, tease. Therapy with these inhibitors reduces vpr, and upu). Alternatively, it can be spliced only a few HIV levels and increases CD4 T-lymphocyte cell counts. times to produce the major gag, pol, and enu products Similar benefits occur with drugs that inhibit the re- that form the virion. verse transcriptase enzyme. The rev protein binds to the enu gene to decrease 4) env codes for the ENVelope proteins that, once splicing. So it REVS up the reading of gag, pol, and enu glycosylated, form the glycoprotein spikes gp 120 and to produce virions! gp 41. Gp 120 forms the head and gp 41 the stalk. To- 3) nefs function is uncertain, as experiments have gether they are called gp 160 and bind to CD4 recep- demonstrated that it can both positively and negatively tors on T- cells. regulate HIV expression. Recent studies have shown that persons infected Regulatory proteins are encoded by the regulatory with nef deficient HIV-1 do not develop AIDS and do : tat, rev, and nef. Three others (uif, vpr, and not suffer T cell destruction. So nef may play a critical vpu) have poorly understood actions in vivo and will not role in HIV pathogenesis, and vaccines that target nef be discussed. may be useful.

194 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

Figure 25-6

Genome Heterogeneity of AIDS cases is on the decline in Western Europe, Aus- tralia, and the United States, the CDC estimates that One of the reasons we are having so much trouble 650-900 thousand persons are currently infected with developing a vaccine against HIV is that it possesses HIV in the United States. the ability to change its genome in a critical area. The disease is transmitted in 2 patterns: 1) In the Within the enu gene, particularly the area encoding the Americas and Europe 90% of cases are among homo- gp 120 glycoprotein, lie hypervariable regions, where sexuals and IV drug users, resulting in more infected point mutations occur. In fact, duplications and dele- men then women. 2) In developing areas, namely sub- tions also occur here, and they occur in multiples of 3 Saharan Africa, spread is heterosexual with equal male to preserve the codon reading frame! Even the gene and female infection. coding for reverse transcriptase undergoes frequent The HIV virus is spread by the parenteral route, mutations. In fact, it has one of the highest error rates much like hepatitis B virus. This occurs with: (mutation rates) described, leading to HIV strains resistant to zidovudine and other reverse transcriptase 1) Sexual activity: Heterosexual and homosexual ac- i nhibitor medications. This heterogeneity protects the tivity is the most common mechanism of transmis- virus from the human immune system and vaccine in- sion of HIV. HIV is present in seminal fluid as well duced antibodies. as vaginal and cervical secretions. During or following intercourse, the viral particles penetrate tiny ulcerations in the vaginal, rectal, penile, or urethral mucosa. HIV INFECTION Women are 20x more likely than men to get HIV with Epidemiology and Transmission vaginal intercourse, likely because of the prolonged exposure of the vagina, cervix, and uterus, to seminal As everyone now knows, we are in the midst of a global fluid. Receptive anal intercourse appears to increase the pandemic of HIV infection. It is estimated that 47 million risk of transmission, likely secondary to mucosal trauma persons worldwide have been infected with the HIV virus of the thin rectal wall. Sexually transmitted diseases and close to 14 million have died. Ninety percent of in- also increase the risk of transmission. Organisms such fected persons today live in the developing world and most as Treponema pallidum, herpes simplex virus, Chlamy- are in Africa. In fact, it is estimated that in some countries dia trachomatis, and Neisseria gonorrhoeae cause mu- in Sub-Saharan Africa, one-fourth to one-third of all cosal erosions and may even increase the concentration adults are infected! The HIV epidemic is rapidly spread- of HIV in semen and vaginal fluids. (Inflammation of the ing in South and Southeast Asia. While the total number epididymis, urethra, and vaginal mucosa results in an CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS increase in HIV laden macro-phages and lymphocytes.) with the CD4 molecule for binding of HIV to lympho- Oral sex is much less likely to result in transmission. cytes and macrophages. 2) Blood product transfusion: HIV can be transmitted Patients who fail to produce normal levels of CKR5 in whole blood, concentrated red blood cells, platelets, proteins appear to be resistant to HIV infection, and cer- white blood cells, concentrated clotting factors, and tain lymphocyte derived proteins (RANTES, MIP1-alpha , plasma. Gamma-globulin has not been associated with and MIP1-Beta) that bind to CKR5 apper to inhibit HIV transmission. To reduce the risk of transmission via blood infection. This now opens the door to new classes of products, blood donors are screened for self reported risk drugs that block fusin and CKR5! (Feng, 1996; Cohen, factors and serologic markers of HIV infection. The latter 1996; Deng, 1996; Dragic, 1996; Alkhatib, 1996). includes screening for antibodies to HIV-1 and HIV-2 (by The viral RNA is reverse transcribed into DNA in the ELISA) and for p24 antigen. This approach has reduced cytoplasm. Double-stranded DNA is formed and trans- the risk of blood product transmission to 1 in 500,000 ported into the nucleus, where integration into the host units transfused. DNA occurs. The integrated DNA may lie latent or may 3) Intravenous drug use with needle sharing: This activate to orchestrate viral replication. There is some has led to growing numbers of infected persons in U.S. evidence that certain infections, such as with tubercu- urban centers. losis, PCP, cytomegalovirus, herpes, Mycoplasma or im- 4) Transplacental viral spread from mother to fe- munizations, will activate T-cells and may promote tus: The rate of transmission is about 30%, and in- viral replication within the T-cells. Stimulation of T- fection occurs transplacentally, during delivery, and cells results in production of proteins that bind to the perinatally. HIV LTR, promoting viral transcription. 5) Note for students and health care providers: The Following viral replication the new capsids form risk of contracting HIV from a stick with a needle, con- around the new RNA dimers. The virion buds through taminated with HIV infected blood, is 3 out of a thousand the host cell membrane, stealing portions of the mem- (0.3%). The risk is much lower for accidental body fluid brane to use as an envelope, leaving the T-cell dead. contact with broken skin. There is virtually no risk in touching an HIV infected patient, unless there is contact Immunology and Pathogenesis with blood or body fluid. The risk goes up if the injury is deep, the needle was in a patient's artery or vein, or had Following initial infection, HIV can begin replication blood visible on it, or if the patient has a high viral load i mmediately, resulting in rapid progression to AIDS, or (MMWR, 1995). To put the risk of transmission of HIV by there can be a chronic latent course. The former, most needle stick (0.3% transmission risk) into perspective, common pattern occurs in 3 stages starting with initial the risk of transmission of Hepatitis B virus after a nee- i nfection, marked by an acute mononucleosis-like viral dle stick from a patient who is Hepatitis B e antigen pos- illness. This progresses for a variable number of years itive is about 30%, and for Hepatitis C virus is about 3%. (median 8 but range of less than 1 to greater than 20) of 6) Epidemiologic evidence indicates that the virus disease-free latency. After AIDS develops most patients is NOT spread by mosquito bites or casual contact die within 2 years if they do not receive effective anti- (kissing, sharing food). There is NO evidence that retroviral therapy (Fig. 25-7). saliva, urine, tears, or sweat, can transmit the virus. 1) An acute viral illness like mononucleosis (fever, Cell Infection malaise, lymphadenopathy, pharyngitis, etc.) develops i n 80% about 1 month after initial exposure. There are Once the HIV virion is in the bloodstream, its gp 160 high levels of blood-borne HIV (viremia) at this stage, (composed at gp 120 and gp 41) glycoproteins bind to the and the viruses spread to infect lymph nodes and CD4 receptor on target cells. This CD4 receptor is pres- macrophages. An HIV-specific immune response arises, ent in high concentration on T-helper lymphocytes. resulting in decreased viremia and resolution of the These cells are actually referred to as CD4+ T-helper above symptoms. However, HIV replication continues cells. Other cells that possess CD4 receptors in lower in lymph nodes and peripheral blood. concentrations and which can become infected are 2) A clinical latency follows for a median of 8 years macrophages, monocytes, and central nervous system during which there are no symptoms of AIDS, although dendritic cells. Following HIV binding to the CD4 re- some patients develop a dramatic generalized lym- ceptor, the viral envelope fuses with the infected host phadenopathy (possibly secondary to an aggressive im- cell, allowing capsid entry. mune attack against HIV harbored in the lymph nodes). Part of the mystery of how HIV binds to the CD4 re- This is not a true viral latency without viral replication; ceptor is as follows. There are two cell surface proteins, HIV continues to replicate in the lymphoid tissue and fusin and CKR5, that are produced by T-lymphocytes there is a steady gradual destruction of CD4 T-lym- and macrophages, respectively. They serve as co-factors phocytes (helper) cells. CD4+ T-helper cells are the

196 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

number one target of HIV. The virus reproduces in 2) CD4+ T-cell count of 400-200 (about 7 years): these cells and them. Constitutional symptoms (weight loss, fever, night Toward the end of the 8 years, patients are more sus- sweats, adenopathy) develop as well as annoying skin ceptible to bacterial and skin infections, and can de- infections, such as severe athletes foot, oral thrush velop constitutional (systemic) symptoms such as fever, (Candida albicans), and herpes zoster. Bacterial infec- weight loss, night sweats, and adenopathy. tions, especially Mycobacterium tuberculosis, become 3) AIDS develops for a median of 2 years followed by more common as CD4 counts drop below 400!! death. AIDS is now defined as having a CD4 T-lympho- 3) CD4+ T-cell count less than 200 (about 8 years): cyte count of less than 200 (with serologic evidence As the immune system fails, the serious opportunistic of HIV infection such as a positive ELISA or west- killers set in, such as Pneumocystis carinii pneumonia, ern blot test) and/or one of many AIDS-defining oppor- Cryptococcus neoformans, and Toxoplasma gondii. tunistic infections, which are infections that usually only 4) CD4+ T-cell count less than 50: At this level the patients with AIDS develop. These include Candida immune system is almost completely down. Mycobac- esophagitis, Pneumocystis carinii pneumonia, the malig- terium avium-intracellulare, normally only causing in- nancy Kaposis sarcoma, and many others. fection in birds, causes disseminated disease in the AIDS patients. Cytomegalovirus infections also rise as Fig. 25.7. The HIV the count moves from 50 to zero. (acute viral illness, clinical latency, and AIDS) as CD4+ T-cells decline over time, and the opportunistic infec- Viral Load tions that develop at specific CD4 T-cell counts. CD4 counts are used to determine severity of HIV in- 1) Normal CD4+ T-cell counts are 1000 cells/µl blood. fection, risk of opportunistic infection, prognosis, and re- In HIV-infected persons the count declines by about 60 sponse to anti-viral therapy. We can now measure plasma cells/ml blood/year. HIV RNA by the polymerase chain reaction (PCR) or CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS branched chain DNA assay. There is mounting evidence phocytes, and other immune system effectors. A severe that higher plasma HIV RNA levels (viral load) correlate immunodeficiency state follows the loss of CD4+ T-cells. with a greater risk of opportunistic infection, progression Multinucleated giant cells: This T-cell to T-cell fu- to AIDS, and risk of death (Mellors,1996; Galetto-Lacour, sion allows the virus to pass from an infected cell to an 1996). CD4 counts are still the best predictor of a patient's uninfected cell without contacting the blood. This current risk for particular opportunistic infections. David may protect the virus from circulating antibodies. Ho has popularized the train analogy to explain the pre- B-Lymphocytes: HIV does not actually infect the B- dictive values of HIV viral load and CD4 counts. Viral load cells; however, B-cell dysfunction does occur with HIV tells you the speed at which the train is heading for the infection. There is a polyclonal activation of B-cells, re- cliff (low CD4, development of opportunistic infections sulting in an outpouring of immunoglobulins. This and death) while the CD4 count tells you where the train hypergammaglobulinemia results in immune-com- currently is! For example, if a patient has a CD4 count of plex formation and autoantibody production. The most 450 cells/mL and a viral load of >106 copies/µL that pa- important dysfunction that occurs is a diminished abil- tient is at low risk for developing Pneumocystis carinii ity to produce antibodies in response to new antigens or pneumonia today (CD4>200 cells/micL) but is at great risk immunization. This is very serious in infants with AIDS in the future for rapid CD4 count decline, opportunistic in- because they cannot develop humoral immunity to the fection and death if not treated. vast number of new antigens they are exposed to. Monocytes and macrophages: HIV infects these Mechanism of T-Cell Death cells and actively divides within them. However, these cells are not destroyed by HIV. This is clinically signifi- The CD4 receptor appears to be involved in T-cell cant in 2 ways: death. Monocytes and macrophages, which possess lower CD4 receptor concentrations, are not destroyed as 1) Monocytes and macrophages serve as reservoirs extensively as are T-cells. for HIV as it replicates, protected within these cells When a T-helper cell is infected, and the virus produces from the immune system. its structural proteins, gp 160 (composed of gp 120 and gp 2) These cells migrate across the blood-brain barrier, 41) is integrated into the T-helper cell cytoplasmic mem- carrying HIV to the central nervous system. HIV causes brane. The virion will bud at the site of gp 160 insertion, brain disease, and the predominant cell type harboring stealing this portion of the membrane to form its envelope. HIV in the central nervous system is the monocyte- Three mechanisms ofT-cell death have been observed: macrophage line. 1) When the virion is budding, the gp 160 (in the T- BIG PICTURE: HN infection diminishes CD4 cell membrane) may bind to adjacent CD4 receptors on T-lymphocyte (helper) cell numbers and function. the same T-helper cell membrane, tearing the T-cell The CD4 T-helper cells are involved in all immune membrane and destroying the cell. responses. So all immune cells have some kind of 2) A second phenomenon occurs between infected altered function. As T-cell numbers decline, the cells and noninfected CD4 cells. The gp 160 in the in- host becomes susceptible to unusual infections fected cells binds to other CD4 T-helper cells, resulting and malignancies that normally are easily con- in cell-to-cell fusion. One infected cell can fuse with as trolled by an intact immune system. many as 500 uninfected CD4+ T-helper cells, forming multinucleated giant cells. ACQUIRED IMMUNODEFICIENCY 3) Gp 160 in the T-cell membrane may mark the cell SYNDROME (AIDS) as non-self, resulting in autoimmune T-cell destruction by cytotoxic CD8 T lymphocytes. Fig. 25-8. The acquired immunodeficiency syndrome (AIDS) is an extremely complex disease. To better un- HIV probably also kills T-cells directly by inhibiting derstand this complexity, consider 2 processes that oc- host cell protein synthesis. cur. The HIV virus causes 1) direct viral disease and 2) disease secondary to the immunodeficiency state. What Is the Clinical Significance of These Events? 1) Direct viral disease Constitutional (widespread body) symptoms T-Cell death: A healthy person has about 1000 Neurologic damage CD4+ T-helper cells per milliliter of blood. HIV-induced 2) Disease secondary to the immunodeficiency state T-cell death results in a decline of about 60 CD4+ T- Failure of the immune surveillance system that cells/µl a year. The T-helper cell plays a vital role in the prevents malignancies orchestration of the cell-mediated immune system, acti- Secondary infections by pathogens and normal vating and recruiting macrophages, neutrophils, B-lym- flora (opportunistic infections)

198 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

Figure 25-8

Constitutional Illness gressive decline in cognitive function referred to as the AIDS dementia complex. Meningeal infection results in AIDS patients suffer from night sweats, fevers, en- aseptic meningitis. The spinal cord can become infected, larged lymph nodes, and severe weight loss. The weight resulting in myelopathy, and peripheral nerve involve- loss is often referred to as the wasting syndrome. ment results in a neuropathy.

Neurologic Disease Malignancies

The HIV virus is carried to the central nervous sys- AIDS patients suffer from a high incidence of B-cell tem by the monocyte-macrophage cells. It is unclear at lymphoma, often presenting as a brain mass. Half of this time whether the neuronal damage is caused by the B-cell lymphomas in AIDS patients are found to contain inhibition of neuronal growth by the HIV envelope Epstein-Barr virus DNA. proteins or an autoimmune damage caused by the in- Another common AIDS associated malignancy is fected monocyte-macrophages themselves. Kaposis sarcoma. Most cases of Kaposis sarcoma Many patients with HIV infection suffer from some (96%) occur in homosexual men, which suggests that form of neurological dysfunction. The brain can suffer there may be a co-factor, which appears to be a new diffuse damage (encephalopathy) resulting in a pro- herpes virus called HHV-8. HHV-8 DNA sequences

199 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS have been found in Kaposi's sarcoma, and antibodies of AIDS patients with cryptococcal meningitis will pre- to HHV-8 are found in high concentrations in most pa- sent with headache, mental status changes, or tients (80%) with Kaposi's sarcoma and in 35% of ho- meningeal signs. For example: A normal host with mosexual HIV positive men (Moore, 1995; Kedes, meningitis would have meningeal inflammation with 1996; Gao, 1996). The lesions are red to purple, meningismus (positive Kernig's and Brudzinski's sign, plaques or nodules, and arise on the skin all over the stiff neck, headache). An AIDS patient can have a rag- body. The course can range from nonaggressive dis- i ng meningitis with only fever. You must have a high ease, with limited spread and only skin involvement, level of suspicion and always consider doing a lumbar to an aggressive process involving skin, lymph nodes, puncture, for cerebrospinal fluid testing, on AIDS pa- l ungs, and GI tract. tients with fever. (More on page 149). Histoplasma capsulatum and Coccidioides im- O I mitis: These fungi produce disseminated disease in AIDS patients, infecting meninges, lungs, skin, and The most common manifestation of AIDS is the sec- other areas. (More on page 147). ondary infection by opportunists. These are bugs that are normally pushovers to the intact immune system Viral Infections but wreak havoc in the absence of T-helper defenses (see Fig. 25-7.). Herpes zoster: Painful vesicles develop in dermatomal distribution as the varicella-zoster virus ven- Bacterial Infections tures forth from its latency in the dorsal sensory ganglia. AIDS patients can also develop disseminated AIDS patients often have many permanent in- non-dermatomal zoster. dwelling intravenous lines or are in the hospital with Epstein-Barr virus, another herpes family virus, is central venous lines. These serve as entry points for bac- thought to cause oral hairy leukoplakia (OHL). OHL teremia caused by Staphylococcus aureus or Staphylo- usually develops when CD4 counts are <400 and is coccus epidermidis. characterized by white hairlike projections arising from The poorly functioning B-cells and their impaired hu- the side of the tongue. This is differentiated from Can- moral immunity result in more infections with encap- didal thrush by the fact that OHL will not rub off with sulated organisms such as Haemophilus influenzae and a tongue blade. Streptococcus pneumoniae. Herpes simplex: Viral infection results in severe Mycobacterium tuberculosis: Remember the piv- genital and oral outbreaks. otal role of cell-mediated immunity in defense against Cytomegalovirus (CMV): This virus can cause Mycobacterium tuberculosis. AIDS patients have a chorioretinitis and blindness. Visual compromise must higher chance of tuberculosis reactivation (about 10% be looked into carefully in AIDS patients because it can chance per year). (More on page 105). represent the retinal lesions of CMV or brain masses of Mycobacterium avium-intracellulare (MAI): toxoplasmosis and lymphoma. CMV can also cause This atypical mycobacterium, also called Mycobacterium esophagitis (pain with swallowing) and diarrhea. avium-complex (MAC), can be isolated from many sites (GI tract, liver, bone marrow, lymph nodes, lungs, blood) in infected patients. It causes a smoldering, wasting dis- Protozoal Infections ease characterized by fever, night sweats, weight loss, Pneumocystis carinii pneumonia (PCP): This is and often diarrhea (GI tract infection) and elevated liver the most common opportunistic infection. Without pro- function tests. (More on page 106). phylactic treatment there is a 15% chance each year Fungal Infections of infection when the CD4+ T-cell count is below 200. AIDS patients who develop PCP have cough and Candida albicans: This yeast is very common in hypoxia. The chest X-ray can be normal or show an in- HIV-infected patients. It causes oral thrush and terstitial infiltrates. Pneumothorax complicates 2% of esophagitis. Thrush looks like white plaques on the oral PCP cases. About 80% of AIDS patients will get this at mucosa and when scraped off with a tongue blade leaves least once in their lifetime unless prophylactic antibi- a red bleeding base. (More on page 150). otics are taken. (More on page 235). Cryptococcus neoformans: This fungus causes a Toxoplasma gondii: This parasite causes mass le- meningitis in about 10% of AIDS patients. Fever, nau- sions in the brain in 15% of AIDS patients. Patients sea, and vomiting may hint at cryptococcal meningitis. present with fever, headache, and focal neurologic Important: AIDS patients are similar to the elderly and deficits (seizure, weakness, aphasia). A CT scan will children: Without a full immune system they often show contrast-enhancing masses in the brain. (More on do not exhibit meningeal inflammation. Only 25% page 234).

200 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

Cryptosporidium, Microsporidia, and Isospora Prevention belli. These parasites cause chronic diarrhea in patients with AIDS. (More on page 231). Education to avoid high-risk activities (needle sharing, multiple sexual partners, unprotected sex). Screening blood products with ELISA and p24 DIAGNOSIS of HIV and AIDS antigen. Following infection with HIV, viral RNA or antigens (such as p24) can be detected in the blood within weeks. Vaccine Development Three to 6 weeks later antibodies against HIV antigens The goal of vaccination is to stimulate an immune re- appear. The enzyme-linked immunosorbent assay sponse that will counter a subsequent infection. Most (ELISA) test detects antibodies. This test is very sensi- vaccines stimulate an antibody response to a viral anti- tive at detecting HIV infection (sensitivity of 99.5%) but gen, resulting in the neutralization of the virus. Persons it often gives false positive results. infected with HIV develop antibodies against HIV de- To decrease this rate of false positives, a second terminants. Early in HIV infection antibodies arise that ELISA is recommended on the original sample and if bind to a hypervariable portion of the envelope glyco- In this this is positive again, do a western blot test. protein gp 120, called the V3 loop. These V3 specific test, HIV antigens (gag, pol, and enu proteins) are antibodies will neutralize only the exact strain of HIV separated in bands on paper by molecular weight. The that elicited the antibody. Chimpanzees given V3 neu- person's serum is then added to this paper. If the tralizing monoclonal antibody (passive immunization) serum contains antibodies against HIV antigens they and chimpanzees actively immunized with the V3 enve- will stick to the antigens on the paper. Lastly, anti- lope glycoprotein were protected from injected cell-free human antibodies (labeled with enzymes) are added; HIV virus of the same strain. These vaccines only pro- these stick to the antibodies on the antigens, lighting tect against a virus with the exact same V3 hypervari- up "bands" on the paper. A western blot is considered able region and only during peak immunity. positive if it has bands to 2 HIV gene products (p24, Another later developing antibody response occurs gp41, gp120) (see Figs. 25-5 and 25-6). against the CD4 binding domain (gp 160, composed Direct viral culture in cell lines, p24 antigen capture, of gp 120 and gp 41); this domain is responsible for and polymerase chain reaction (PCR) and BDNA are binding to T-lymphocyte CD4 receptors. The CD4 bind- used to identify HIV whole virus, p24 antigen, and ing domain antigen is more conserved, meaning that it DNA/RNA respectively. is similar in many HIV strains. Antibodies against this HN infection should be suspected when an at-risk domain will prevent viral binding to the CD4 receptor, individual (homosexual, IV drug user, sexual partner neutralizing HIV-1 in vitro. of an at-risk individual, etc.) develops constitutional Since the above antibody responses develop with HIV symptoms such as fevers, night sweats, and generalized infection and with all the ongoing efforts to develop a adenopathy, or suffers from recurrent bacterial infec- vaccine, why are we told that successful vaccination is a tions, tuberculosis, skin zoster or tinea infections, or distant reality?!? oral thrush (Candida). There are many challenges to the development of a AIDS is diagnosed when the CD4 T-lymphocyte count successful vaccine against HIV-1: is less than 200 (with serologic evidence of HIV infection such as a positive ELISA or western blot test) and/or the 1) Rapid mutation: HIV envelope glycoproteins patient has one of many AIDS-defining opportunistic in- mutate rapidly, so there are many different strains. The fections, which are infections that usually only patients rapidly mutating V3 loop of gp 120 and the reverse tran- with AIDS develop. These include Candida esophagitis, scriptase enzyme combined with rapid viral reproduc- Pneumocystis carinii pneumonia, the malignancy Ka- tion over a long disease course results in different posi's sarcoma, and many others. "quasi-species," even in the same person. A vaccine would need to target a conserved region like the CD4 CONTROL, TREATMENT, CURE? binding domain. 2) HIV is transmitted from cell-to-cell: With Efforts directed toward viral control are moving along syncytial giant-cell formation, HIV is able to pass 4 lines: from one cell to another without contacting the bloodstream that carries antibodies. The virus can thus 1) Prevention of HIV viral infection. escape the antibody-mediated or humoral immune 2) Vaccine development. system. Protection against HIV infection also requires 3) Limiting growth of HIV, once infection has occurred. cell-mediated immunity: HIV proteins in an infected 4) Treating the opportunistic infections that ulti- cell are expressed on the cell surface associated with mately cause death. class I molecules of the major histocompatibility

201 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS complex. Circulating HIV-specific cytotoxic T-lympho- thus preventing HIV from binding to the CD4+ T-helper cytes will recognize this complex and lyse the cell, de- cells. Simian immunodeficiency virus (SIV), a close rela - stroying HIV inside. This cell-mediated response does tive to HIV-2, infects primates. Monkeys with SN were occur in patients with HIV infection, and a successful given soluble CD4 with improvement in their disease (in- vaccine would have to stimulate this arm of the im- creased T-lymphocyte counts and reduced viral load), mune system. (Letvin, 1993) 3) Poor animal model: One would like an animal For further reading refer to: Graham BS, Wright PF. model that is easily obtainable, cheap, and would develop Drug therapy: Candidate AIDS vaccines. N Engl J Med an AIDS-like illness when infected with HIV. There is no 1995;333:1331-9. such model. The only species that can be infected are the great apes; they are expensive, scarce, and do not get Limiting Viral Growth AIDS when infected with HIV. However, their antibody response to HIV can be followed, and they do get an Triple drug therapies-Highly Active Antiretroviral AIDS-like illness when infected with SIV (which shares Therapy (HAART) have been used to bolster the im- sequence homology with HIV-2). mune system in HIV-positive and AIDS patients, which has decreased the rate of development of opportunistic infections, including Mycobacterium avium, Current Vaccine Research Efforts CMV retinitis, & oropharyngeal candidiasis. Please see 1) Live viruses can be altered or attenuated so they Chapter 29, the anti-viral antibiotic chapter, which ex - lose their virulence while still stimulating immunity tensively discusses current anti-HIV drug strategies. (e.g., polio and measles vaccine). This type of vaccine would stimulate cellular and humoral immunity, as Treating the Opportunistic infections well as mucosal immunity. Studies with live viruses have used SIV and HIV-2, which have been made non- 1) Pneumocystis carinii pneumonia (PCP): pathogenic secondary to gene deletions. The limitation Trimethoprim and sulfamethoxazole are given prophy- of this approach involves the danger of new mutations lactically when CD4+ T-cell counts drop below occurring in the non-pathogenic live virus that might 200-250. Greater than 90% of PCP infections are being make it pathogenic. Also, the great apes do not develop prevented with this prophylactic intervention! an AIDS-like disease, so how can we be sure such a vac- 2) Toxoplasmosis: Brain lesions are treated with cine is non-pathogenic? another tetrahydrofolate reductase inhibitor/sulfa com- 2) A recombinant HIV-1 envelope glycoprotein bination called pyrimethamine/sulfadiazine. Patients vaccine can be made by splicing the HIV gene, which improve rapidly. In fact, if there is no brain mass codes for envelope glycoprotein antigens (V3 loop, CD4 shrinkage (as seen by CT scan) by 2-3 weeks, then the binding domain, or others), into the DNA of tumor-cell diagnosis of toxoplasmosis is unlikely. Brain biopsy lines. The tumor cells will produce the HIV envelope should then be done to determine whether the mass is a glycoprotein in mass quantities that can be used as a B-cell lymphoma. vaccine. The hepatitis B vaccine is made in this manner, The same medicine (trimethoprim and sulfamethox- with cell lines producing the hepatitis B surface antigen azole), used for PCP prophylaxis, also prevents toxo- (HBsAg). As mentioned above, however, these vaccines plasmosis! It prevents two birds with one stone. only protect against a virus with the exact same anti- 3) Mycobacterium tuberculosis and Mycobac- genic region used in the vaccine and only during peak terium avium-intracellulare: Treatment of tubercu- immunity. They also fail to activate a cytotoxic T-lym- losis is covered in Chapter 15. phocyte response. Azithromycin or clarithromycin can be given 3) Live recombinant organisms can be used to daily for prophylaxis against future MAI infections. carry and express HIV genes. The vaccinia virus (live 4) CMV: Treatment with ganciclovir or foscarnet can attenuated virus used for smallpox vaccine), bacille Cal- prevent progression of visual loss. mette-Guerin (bacteria used for Mycobacterium tuber- 5) Herpes, Varicella-zoster: Acyclovir. culosis vaccine), and adenovirus strains are some of the 6) Candida albicans: Oral clotrimazole, nystatin, organisms used as vectors in vaccine experiments. Some or fluconazole preparations for thrush and esophagitis. studies have demonstrated an antibody and T-lympho- Systemic fungal infections are treated with intravenous cyte response to proteins produced by these recombi- amphotericin B or fluconazole. nant organisms. 7) Bacteria: Appropriate antibiotics. 4) Direct intramuscular injection of HIV genes may elicit humoral and cell-mediated immune responses. AIDS patients are now surviving for prolonged peri- 5) Soluble CD4 receptors delivered to cultured cells ods with CD4+ T-cell counts approaching zero. They are block HIV infection. The CD4 receptors bind to HIV gp 120, often on more than 10 different medications.

202 CHAPTER 25. RETROVIRIDAE, HIV, AND AIDS

A Final Word Haseltine WA. Molecular biology of the human immunodeficiency virus type 1. The FASEB journal 1991:2349-2360. AIDS is a disease that has no dignity, a disease that Kedes DH, et al. The seroepidemiology of human herpes virus cripples the immune system, allowing the scourge of all 8 (Kaposi's sarcoma-associated herpesvirus): distribution of infestations. You are becoming a physician in the dawn infection in KS risk groups and evidence for sexual trans- of a new epidemic, and you will certainly play a role in mission. Nature Medicine 1996;2:925-8. the control of this epidemic. Lackritz EM, Satten GA, et al. Estimated risk of transmission of the human immunodeficiency virus by screened blood in the United States. N Engl J Med 1995;333:1721-5. References Letvin NL. Vaccines Against Human Immunodeficiency Virus- Alkhatib G, et al. CC-CKR5: a RANTES, MIP-la, MIP-1 beta Progress and Prospects. N Engl J Med 1993;329:1400-1405. receptor as a fusin cofactor for macrophage-trophic HIV-1. Mellors JW, et al. Prognosis in HIV-1 infection predicted by Science 1996;272:1955-8. the quantity of virus in plasma. Science 1996;272:1167-70. Case-control study of HIV seroconversion in health-care work- Moore PS, Chang Y. Detection of herpesvirus-like DNA se- ers after percutaneous exposure to H1V-infected blood- quences in Kaposi's sarcoma in patients with and those France, United Kingdom, and United States, January without HIV infection. N Engl J Med 1995;332:1181-5. 1988-August 1994. MMWR 1995;44:929-33. Pantaleo G, Graziosi C, Fauci A. The immunopathogenesis of Cohen J. HIV cofactor found. Science 1996;272:809-10. human immunodeficency virus infection. N Engl J Med Deng H, et al. Identification of a major co-receptor for primary 1993;328:327-335. isolates of HIV-1. Nature 1996;381:661-6. Watkins BA, Klotman MF, Gallo RC. Human immunodefi- Dragic T, et al. HIV-1 entry into CD4 T cells is mediated by the ciency viruses. In: Mandell Bennett VF, Polin R, eds. chemokine receptor CC-CKR5. Nature 1996;381:667-73. Principles and Practice of Infectious Diseases. 4th edition. Fauci AS, Lane HC. Human immunodeficiency virus (HIV) New York: Churchill Livingstone 1995;1590-1606. disease: AIDS and related disorders. In: Isselbacher, Braun- wald, et al., eds. Harrison's Principles of Internal Medicine. Recommended Review Articles: 13th ed. New York: McGraw-Hill, 1994;1566-1618. Feng Y, et al. HIV-1 entry cofactor: functional CDNA cloning Esparza J and Bhamarapravati N. Accelerating the develop- of a seven-transmembrane, G protein-coupled receptor. Sci- ment and future availability of HIV-1 vaccines: why, when, ence 1996;272:872-7. where, and how? Lancet 2000;355:2061-2066. Galetto-Lacour A, et al. Prognostic value of viremia in patients Harrington M and Carpenter CC. Hit HIV-1 hard, but only with long-standing human immunodeficiency virus infec- when necessary. Lancet 2000;355:2147-2152. tion. J Infect Dis 1996;173:1388-93. Kovacs JA and Masur H. Prophylaxis against opportunistic in- Gao SJ, et al. KSHV antibodies among Americans, Italians, fections in patients with human immunodeficiency virus in- and Ugandans with and without Kaposi's sarcoma. Nature fection. N Engl J Med 2000;342:1416-1429. Medicine 1996;2:925-8. Graham BS, Wright PF. Drug therapy: candidate AIDS vaccines. N Engl J Med 1995;333:1331-9.

203 CHAPTER 26. HERPESVIRIDAE

Figure 26-1 We all probably have at least 1 of the herpes family Both CMV (beta subgroup) and Epstein-Barr virus viruses living in a latent state in our bodies right now! (gamma subgroup) have less cytopathic effects. Even before entering medicine we have seen people with Patients with compromised cell-mediated im- herpesviridae infections. People with "fever blisters" of mune status are more likely to suffer from severe her- HSV-1, the child with multiple blisters covering the pesviridae infections such as disseminated HSV or body with chickenpox (varicella-zoster), and the teenage multi-dermatomal zoster. CMV frequently causes dis- friend who had to miss school with mononucleosis ease in AIDS patients. (Epstein-Barr virus). There are some generalities that the herpesviridae Herpes Simplex Virus 1 (HSV-1) share: Antibodies to HSV-1 are present in 90% of adults by 1) They can develop a latent state. the fourth decade, with those from lower socioeconomic 2) The members in the sub-family alpha have a cyto- classes being more likely to acquire HSV earlier. Most pathic effect on cells, which become multinucleated primary infections are not even noticed. In fact, fewer giant syncytial cells with intranuclear inclusion than 1% are clinically apparent. When there are clinical bodies. symptoms, patients will present with: 3) Herpesviridae are held at bay by the cell-mediated immune response. 1) Gingivostomatitis: Painful swollen gums and mucous membranes with multiple vesicles. Fever and Latency: During the primary infection the viruses systemic symptoms can accompany the infection, and migrate up the nerves to the sensory ganglia and reside the disease will resolve in about 2 weeks. Vesicles can there. The viruses rest there until reactivation occurs also appear on areas of the skin where viral entry has through some stress, such as menstruation, anxiety occurred. states, fever, sunlight exposure, and weakening of the 2) Reactivation: About one fourth of previously in- cell-mediated immune system, as with AIDS or chronic fected people have reactivation infection during disc ase. The viruses then migrate out to the peripheral stressed states. AIDS patients can present with severe skin via the nerves to cause local destruction. reactivation of HSV. Fig. 26-1. Captain Herpes hiding in latency in his 3) Herpetic keratitis: the most common infectious dorsal sensory ganglia fortress. cause of corneal blindness in the United States. 4) Encephalitis: HSV-1 is the most common cause Cytopathic effect: The herpesviridae that cause cell of viral encephalitis in the U.S. Infection of the brain destruction are the alpha sub group viruses (herpes cells occurs, with cell death and brain tissue swelling. simplex virus 1 and 2, and varicella-zoster). This cell de- Patients present with sudden onset of fever and focal struction results in the separation of the epithelium and neurological abnormalities. HSV-1 must always be causes blisters (vesicles). Microscopic study of skin considered, because herpes is one of the few treatable biopsies or scrapings from blister bases in herpes sim- causes of viral encephalitis!! plex, chickenpox, and zoster all reveal multinucleated giant cells and intranuclear inclusion bodies. Viral pro- Herpes Simplex Virus 2 (HSV-2) teins are inserted into the host cell plasma membranes, resulting in cell fusion to form multinucleated giant HSV-2 is antigenically distinct from HSV-1. It com- cells. Intranuclear inclusions are considered to be areas monly causes genital disease that is sexually trans- of viral assembly. mitted. However, HSV-2 can also cause oral/skin/eye

204

CHAPTER 26. HERPESVIRIDAE

disease, and HSV-1 can cause genital herpes. The dif- out along sensory nerve paths and cause vesicles simi- ference is unimportant clinically because both can cause lar to those of chickenpox. However, with this reactiva- the same symptoms, and the treatment is the same. Pa- tion infection, the vesicles appear in a dermatomal tients with genital herpes get vesicles on the vagina, distribution, almost always unilaterally. cervix, vulva, perineum, and glans and shaft of the penis. The vesicles are painful, with burning and itching, Varicella often associated with urination. ( Chickenpox) Neonatal Herpes VZV is highly contagious, infecting up to 90% of those exposed. It occurs in epidemics, usually during winter HSV infection during pregnancy can result in and spring and involves children who have not previ- transplacental viral transfer. The infection of the fetus ously been exposed. About 90% of the general adult pop- can cause congenital defects or intrauterine death. The ulation have contracted VZV in childhood. neonate can also acquire the illness during delivery if The virus infects the respiratory tract and replicates the mother is having an active genital infection. for a 2-week incubation period, followed by viremia (viral dissemination in the bloodstream).

Fige 26-2 Fige 26-3 Fig. 26-2. Death, carrying his TORCH, visits the pregnant mother and her baby. Remember that herpes is one of the TORCHES organisms that can cross the Fig. 26-3. In varicella (chickenpox), fever, malaise, blood-placenta barrier: and headache are followed by the characteristic rash. T0: Toxoplasmosis The rash of varicella starts on the face and trunk, R: Rubella spreading to the entire body, including mucous mem- C: Cytomegalovirus branes (pharynx, vagina, etc.). The skin vesicles that HE: HErpes, HIV form are described as dew on a rose petal: a red base S: Syphilis with a fluid-filled vesicle on top. The fluid becomes cloudy, the vesicles rupture, and the lesions scab over. Multiple vesicles arise in patches (crops), and one crop Vaicella-Zoe Vi (VZV) will form as another crop scabs over. So there are lesions As the name implies, this virus causes 2 diseases: in different stages! The vesicles will all scab in about 1 varicella (chickenpox ) and herpes zoster (shingles). week, and the patient then ceases to be contagious. Chickenpox is not caused by the pox viridae!!! Varicella is usually a disease of children. After resolution the Zoster (Shingles) virus remains latent as described previously. Later in life, reactivation can cause the second disease, zoster. Following a stressed state or lowered cell-mediated Once again, with stressors or depressed cell-mediated immunity, the latent varicella-zoster virus in the sen- immunity (usually in the elderly), the virus will migrate sory ganglion begins to replicate and migrate to the pe-

205 CHAPTER 26. HERPESVIRIDAE ripheral nerves. Burning, painful skin lesions develop over the area supplied by the sensory nerves. The diagnosis of zoster is likely when a patient develops a painful skin rash that overlays a specific sensory der- matome

Fig. 26-4. A) 55-year-old male with left, second trigeminal (V2) nerve involvement; B) 76-year-old female with left T5-6 involvement. Since this is the same virus that causes chickenpox, children and adults who have never contracted varicella can get chickenpox from exposure to vesicles.

ConollTeamen A vaccine has been developed for varicella-zoster. However, since varicella causes only mild disease in children, there is controversy,over whether a vaccination program should be instituted. In adults and immunocompromised patients (with leukemia or AIDS, for example), the infection can be more serious, leading to pneumonia and encephalitis. In these groups zoster immune globulin, which consists of antibodies against VZV isolated from patients with zoster, can be given. It will only help if given within days of exposure (not during rash development). Intravenous acyclovir, an antiviral drug, appears to decrease the severity and duration of the infection.

Comegaloi (CMV) CMV is so-named because infected cells become swollen (cytomegaly). As with the other herpesviridae, multinucleated giant cells and intranuclear inclusion bodies are present. CMV causes 4 infectious states: Fige 26-4 1) Ampomaic infecion: About 80% of adults in the world have antibodies against CMV. Most of these infections are asymptomatic. 2) Congenial dieae: CMV is one of the tis (blindness), pneumonia, disseminated infection, and TORCHES (see page 205) organisms that can cross the even death. placenta and cause congenital disease. CMV is the most Interestingly, CMV causes different diseases in 2 dif common viral cause of mental retardation. It also ferent immunocompromised populations: patients with causes microcephaly, deafness, seizures, and multiple AIDS versus patients who have undergone bone mar- other birth defects. It is thought that this organism will row transplantation. In AIDS patients, as the CD4 T- reactivate during a latent state (as do all the her- lymphocyte count drops below 50-100 cells per cc of pesviridae). If reactivation occurs during pregnancy, blood, they frequently develop CMV viremia (CMV in the fetus may become infected. the blood), CMV retinitis (leading to blindness unless 3) Comegaloi mononcleoi: CMV causes treated), and CMV colitis (causing diarrhea). AIDS pa- a mononucleosis syndrome in young adults similar to tients infected with CMV rarely develop pneumonia. In that caused by the Epstein-Barr virus (see Epstein-Barr contrast, bone marrow transplant patients who are virus). CMV antibody positive (representing prior infection 4) CMV can eaciae in the immnocompo- and risk of reactivation) or receive a CMV positive donor mied paien (as do all herpesviridae) to cause retini- bone marrow are at high risk of developing CMV pneu-

206 CHAPTER 26. HERPESVIRIDAE

copies of circular DNA. In some of the cells, the EBV activates and proliferates, and cell lysis with viral release occurs. Interestingly, the transformed cells, which up to this point are acting as malignant (cancer) cells, suddenly disappear, with resolution of the mononucleosis illness. It is thought that the immune system destroys the infecting virus as well as the abnormal B-cells. EBV has been found in the cancer cells of Burkitt's lymphoma, a B-cell lymphoma affecting children in central Africa. Since this cancer does not develop in other areas of the world where EBV infection occurs, it is thought that EBV may be just a co-factor in the malignant transformation. It has been discovered that all Burkitt's lymphoma cells carry a chromosomal arm translocation. This translocation activates a chromosomal oncogene. The infection of B-cells by EBV results in rapid uncontrolled B-cell growth, which may increase the frequency of this key and deadly chromoso- Figure 26-5 mal arm translocation (see more about oncogenes in Chapter 25). monitis. CMV pneumonitis is a severe pneumonia, often Latent EBV infections in immunosuppressed pa- leading to death in this population. The transplant patients can reactivate, resulting in transformation and tients can also develop CMV viremia and colitis but do uncontrolled growth of the B-cell line. Lymphoma and other lymphoproliferative diseases in these patients not develop retinitis. may be secondary to this EBV reactivation. Marrow Transplant = CMV pneumonitis AIDS = CMV retinitis Mononucleosis Fig. 26-5. When you work in the hospital, you will fre- "Mono" is a disease of young adults. As with many vi- quently send special blood cultures for CMV from febrile ral infections, the lower the socioeconomic class, the ear- organ transplant patients (on immunosuppressive lier children are infected and the milder the disease (for drugs that prevent organ rejection), AIDS patients, and example: chickenpox and polio). American teenagers, even children who have leukemia or lymphoma. The living in a higher socioeconomic class with better sani- CMV virus invades the white blood cells (see Epstein- tation, handwashing, etc., are infected later in life Barr virus below) and so there is a higher yield if the through social contact, usually kissing. Thus the refer- buffy coat (layer of white cells in centrifuged blood) is ences to "kissing disease." cultured. Patients with mononucleosis develop fever, chills, sweats, headache, and a very painful pharyngitis. Most Epstein-Barr Virus (EBV) will have enlarged lymph nodes (as the B-cells multiply) EBV, another of the herpesviridae, causes the famous and even enlarged spleens. Blood work reveals a high disease mononucleosis and is involved in certain can- white blood cell count with atypical lymphocytes cers such as Burkitt's lymphoma. seen on the blood smear. These are large activated T- A general concept that helps us understand the way lymphocytes. The blood also has heterophile anti- EBV is involved in these disease processes is transfor- body, which is an antibody against EBV that cross mation. reacts with and agglutinates sheep red blood cells. This can be used as a rapid screening test for mononucleosis Transformation and Malignant Potential (Monospot test). In mononucleosis, EBV infects the human B-cells. HHV 8 EBV actually binds to the complement (C3d) receptor on HHV 8 is a newly identified herpesvirus that appears cells. Once internalized, EBV will change the infected cell so that the cell does not follow normal growth con- to cause Kaposi's sarcoma! (See "Malignancy" subhead- trols. These changed or transformed cells proliferate ing in Chapter 25 for further information.) and pass on copies of the EBV DNA to their progeny. Fig. 26-6. Summary of the herpesviridae. The EBV DNA remains in the latent state as multiple

207 Figure 26-6 HERPESVIRIDAE M. Gladin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ,MedMaster CHAPTER 27. THE REST OF THE DNA VIRUSES CHAPTER 27. THE REST OF THE DNA VIRUSES

Figure 27-1

We have covered in detail the two H's of the HHAPPPy 3) All poxviridae infections produced clinically overt DNA viruses: herpesviridae and hepatitisviridae. We smallpox. Every smallpox attack was obvious, so mem- will now briefly cover the poxviridae, papovaviridae, bers of the World Health Organization could localize adenoviridae, and parvoviridae. communities that needed vaccination. The virus could not hide as an asymptomatic infection or in a latent POXVIRIDAE state. Fig. 27-1. Poxviridae is structurally the most complex of all known viruses. It is a brick-shaped box, POX Molluscum Contagiosum box, and has at its center a large complex DNA in a Fig. 27-2. genome coding for hundreds of proteins. The DNA is or- You mole! You scum! molluscum. A pox virus causes these small, 1-2 mm in diameter, white ganized into a dumbbell shape with structural proteins, bumps that have a central dimple (seen to the right of surrounded by two envelopes. This virus carries many the mole in this figure). They are similar to warts with outs own enzymes and, unlike other DNA viruses, repli- benign hyperproliferation of epithelial cells. You will cates in the cytoplasm. probably first see these lesions on AIDS patients, who frequently develop them. Smallpox Poxviridae do NOT cause chickenpox. Chickenpox is caused by the herpesviridae varicella-zoster. This big PAPOVAVIRIDAE complex pox-box is no chicken! Poxviridae used to cause There are 3 members of the PA-PO-VA VIRIDAE: smallpox. PA: PApilloma virus causes human warts and cervical Why do we say used to cause smallpox? Answer: The cancer. last case of smallpox was in 1977 and it is thought that PO: POlyomavirus has 2 members: human BK and JC this virus has been eradicated from the planet earth!!! virus. Pox has been placed in a box and buried. VA: Simian VAcuolating virus does not infect humans. For more than 3 thousand years this highly contagious virus spread via the respiratory tract, causing pox skin lesions and death. A concerted vaccination and sur- PAPOVAVIRIDAE: veillance program conducted by the World Health Or- ganization brought this tyranny to an end. With these viruses think O O for circular double-stranded DNA (naked icosahedral capsid) The Vaccine and Why It Worked O for round warts 1) A vaccine was developed that induced solid, last- O for round cervix ing immunity. The vaccine contained vaccinia virus, an avirulent form of poxviridae, which induced immunity Papilloma Virus to virulent poxviridae. 2) Smallpox only infected humans. There are no ani- Different strains of the papilloma virus can cause mal reservoirs that can harbor this virus and protect it. warts and cervical cancer.

209 CHAPTER 27. THE REST OF THE DNA VIRUSES

Figure 27-2

Warts BK Polyomavirus There are many strains of papilloma viruses. They 1) As ubiquitous as the Burger King at every high- have a tropism for squamous epithelial cells, and differ- way exit. ent strains like certain anatomic regions: common 2) Causes mild or asymptomatic infection in chil- warts, genital warts, laryngeal warts. Warts are benign dren. hyperproliferations of the keratinized squamous epithelium. Most will resolve spontaneously within 1-2 years. For unclear reasons many people do not develop JC Polyomavirus warts despite the ubiquitous nature of the papilloma Fig. 27-3. JC Polyomavirus is similar to BK but also virus. Perhaps in these unaffected individuals the virus causes an opportunistic infection in immunocompro- remains latent or is effectively controlled by the host im- mised patients called Progressive Multifocal mune system. Leukoencephalopathy (PML). In this disease, patients develop central nervous system, white matter Cervical Cancer damage. Visualize shoppers at J.C. Penney with PML, walking around the store with memory loss, poor Cervical dysplasia and carcinoma are associated with speech, and incoordination. sexual activity and previous exposure to certain strains (type 16 and 18) of human papilloma virus. Think of PAPilloma virus and the PAP smear, which ADENOVIRIDAE is used to detect early dysplastic cellular changes. The The ADENoviridae cause upper respiratory tract in- Pap test has resulted in early detection of cervical dys- fections in children. Visualize A DEN full of coughing, plastic changes and has significantly reduced the pro- sneezing children. Studies estimate more than 10/0 of gression to cervical cancer. childhood respiratory infections are caused by strains of adenoviridae, and virtually all adults have serologic ev- Polyomavirus idence of prior exposure. Infection can result in rhinitis, conjunctivitis, sore throat, and cough. This can some- Two polyoma viruses infect humans. They were times progress to lower respiratory tract pneumonia in named after the initials of the patient from whom the children. virus was discovered. Both are ubiquitous and infect Viral respiratory illness in children in order of fre- worldwide at an early age. quency:

210 CHAPE 27. HE E OF HE DNA IE

Figure 27-4

21 1 CHAPTER 27. THE REST OF THE DNA VIRUSES

#1 RSV It causes a childhood disease called erythema in. #2 Parainfluenza fectiosum (Fifth disease), characterized by fever and a #3 Rhinovirus "slapped face" rash on the cheeks. #4 Adenoviridae Fig. 27-5. Summary of the Rest of the DNA Viruses. PARVOVIRIDAE Fig. 27-4. PARvovirus is the smallest icosahedral virus and has a single strand of DNA. Simple as a Par- ONE golf course!

212 Figure 27-5 THE REST OF THE DNA VIRUSES M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple MedMaster CHAPTER 28. THE REST OF THE: RNA VIRUSES

We have covered in previous chapters some of the RNA viruses: retroviridae, orthomvxoviridae. and paramyxoviridae. We will now briefly review: 1I The ARthropod Borne viruses, which are called arboviruses: These RNA viruses include the togaviridae, flaviviridae, and bunyaviridae. Although not transmitted by arthropods. rubivirus which causes rubella) and hantavirus (hantavirus pulmonary syndrome) will be discussed here because they are members of the togaviridae and bunyaviridae. respectively. 2) The picornaviridae, which are a large group of enteroviruses (ENTERO=Gl, fecal-oral transmission): hepatitis A virus; poliovirus; coxsackie A. B; and echovirus. 3) Viruses that cause the common cold: rhinovirus (really in the picornaviridae family) and coronaviridae. 4) Viruses that cause diarrhea: rotavirus, and call civiridae (which includes the Norwalk virus). 5) Rabies caused by the rhabdoviridae.

THE ARBOVIRUSES Fig. 28-1. The arboviruses include the bunyaviridae, togaviridae, and flaviviridae. All are transmitted by blood-sucking arthropods and cause fever and encephalitis. The legendary U.S. logger Paul Bunyan, wearing a toga, has a rich flavor that attracts mosquitos and other arthropods. lie is about Figure 28-1 to chop down a tree (ARBOL in Spanish). You can WEE: Western equine encephalitis (western U.S. well imagine Paul Bunyan has quite a headache MA Canada). (encephalitis) with that blood-sucker clinging to his EEE: Eastern equine encephalitis (eastern U.S.) toga! .

VEE: Venezuelan equine encephalitis (South and (cen Togaviridae tral America. southern U.S.).

Two members of this family infect humans: Rubivirus 1) Alpha viruses are mosquito-borne and cause Rubivirus is a togavirus, but it is not an arbovirus be enchephalitis, an inflammation of the brain with fever. cause humans are the only infected creatures. Ru- headache. altered levels of consciousness. and focal neu- bivirus causes rubella, which is a mild febrile illness rologic deficits. with a rash. The importance of this virus lies in its ability 2) Rubivirus causes rubella. to cross the placenta and cause terrible congenital Alpha Viruses defects, especially in the first trimester. Rubella ("German measles") is a mild measles-like The 3 main alpha viruses that cause encephalitis all illness. Like measles, rubella is contracted by respiratory infect horses. birds, and humans. They use the mosquito as secretions and has a prodrome of fever and flu a vector. symptoms This is followed by a red maculopapular rash Fig. 28.2. The togaviridae alpha viruses. Picture Paul that sprees from forehead to face to torso to extremities. Bunyan riding on a roller-coaster wearing his toga ( to- Unlike measles, patients are leas "sick," complications such gaviridae), with a mosquito (mosquito vector) on his as en-cephalitis do not occur, and the rash lasts only 3 days, head. The other passengers scream the names of the 3 oat 6. Thus its other name: "3-day measles. "Young main diseases caused by the togaviridae alpha viruses, women can develop self-limiting arthritis with the which are named by geographic region: infection. The R in TORCHES see Fig. 26.21 stands for the feared congenital rubella. The risk of rubella-induced

214

CHAPTER 28. THE REST OF THE RNA VIRUSES

Figure 28-2

congenital defects is greatest early in fetal development Body areas affected in congenital rubella include: when cell differentiation is at a peak. Rubivirus-infected human embryo cells demonstrate chromosomal break- 1) Heart: patent ductus, interventricular septal de- age and inhibition of mitosis. fects, pulmonary artery stenosis, others.

215 CHAPTER 28. THE REST OF THE RNA VIRUSES

2) Eye: cataracts, chorioretinitis, others. West Nile Virus is a flavivirus spread by mosquitoes 3) CNS: mental retardation, microcephaly, deafness. (which feed on infected birds) or blood transfusion. It has A live attenuated rubella vaccine is given to all young been found in Africa, East Europe, West Asia, Middle children in the U. S. It is not recommended for pregnant East and increasingly more frequently in the U.S. Most women because of the theoretical risk of fetal infection. cases present as a mild flu-like illness, but may present However, there is no evidence that this vaccine causes with encephalitis and death, particularly in the elderly. congenital defects. Bunyaviridae Pregnant women are routinely screened for immunity to rubella. If they do not have antibody to rubivirus, Bunyaviridae also cause diseases characterized by they will receive immunization after delivery. fever and encephalitis, such as California encephalitis and Rift Valley fever. For comparison of the bun- Flaviviridae yaviridae with the other arboviruses (toga and flavi), see Fig. 28-10. The flaviviridae share many similarities with the togaviridae: Hantavirus Pulmonary Syndrome The morphology is similar (see Fig. 28-10). They cause encephalitis, with names based on geo- In May 1993 reports began to emerge from the Four graphic location (Japanese encephalitis, Russian en- Corners area of New Mexico, Arizona, Colorado, and cephalitis, etc.). Utah, of an influenza-like illness followed by sudden respiratory failure, frequently culminating in death. Many Fig. 28-3. The flaviviridae are spread by a mos- of these patients were previously healthy adults. The quito vector, infecting humans and birds. etiologic agent is a virus in the bunyaviridae family in the The flaviviridae also cause the febrile diseases yel- genus hantavirus. Hantavirus had previously only been low fever and Dengue fever. associated with the disease hemorrhagic fever with renal failure seen in Asia and Europe. The deer mouse 1) Yellow fever was made famous by the Panama is the reservoir for this virus and exposure to the drop- Canal project. This flavivirus (yellow fever virus) was pings of these rodents accounts for human infections. transmitted to canal workers by mosquitoes. One week More than 50 cases of what is now being called han. later they would develop hepatitis with jaundice (yellow tavirus pulmonary syndrome have been confirmed appearance), fever, backache, nausea, and vomiting. in 14 states. Patients typically present with high fevers, Once the vector was found to be a mosquito, insecti- muscle aches, cough, nausea, and vomiting. Their heart cides were used to control the disease. Spraying contin- and respiratory rate is rapid and blood work may reveal ues in the southern U. S. and Latin American urban a high white blood cell count and a high red blood cell centers, virtually eliminating urban yellow fever. count. The lung capillary permeability is disrupted re- 2) Dengue fever is a mosquito-borne febrile disease sulting in fluid leakage into the alveoli (pulmonary that occurs in the tropics (Puerto Rico, Virgin Islands). edema). The fluid-filled alveoli are unable to deliver It is also called break-bone fever because of the painful oxygen to the bloodstream, and intubation with me- backache, muscle and joint pain, and severe headache. chanical ventilation is required to enhance oxygenation Painful fever! in close to 90% of patients. Death follows in 80% of pa- There is a new severe variant called Dengue hem- tients within a median of 9 days. orrhagic fever, which causes hemorrhage or shock in This illness should be considered in young adults children with a mortality rate of almost 10%. with influenza-like symptoms who develop pulmonary edema. Investigational treatment with ribavirin is currently recommended. (MMWR, 1994; Duchin, 1994). PICORNAVIRIDAE This family of viruses all have similar structure and replication. There are 2 genera: enterovirus and rhinovirus. Enterovirus 1) Enteroviruses have 5 subgroups: a) Poliovirus Figure 28-3 b) Coxsackie viruses A and B

21 6 CHAPTER 28. THE REST OF THE RNA VIRUSES

c) Echovirus 3) Paralytic poliomyelitis: This is the feared man- d) New enteroviruses ifestation of poliovirus infection!!! The viral infection de- e) Hepatitis A stroys presynaptic motor neurons in the anterior horn of These are all called enteroviruses because they infect the spinal cord as well as the postsynaptic neurons leav- intestinal epithelial and lymphoid (tonsils, Peyers ing the horn. The damage to the exiting motor neurons patches) cells. They are excreted in the feces and spread results in clinical manifestations of peripheral motor by the fecal-oral route. The replication in the tonsils also neuron deficits, while the presynaptic neuron damage results in viral shedding from pharyngeal secretions. causes central motor neuron deficits. Poliovirus will be discussed first as it causes the im- This disease is truly terrifying. A mild febrile illness portant paralytic disease, poliomyelitis. Hepatitis A is resolves, 5 to 10 days later the fever recurs, followed by covered in Chapter 24. The remainder will be discussed meningismus and then flaccid asymmetric paralysis. together as there is significant overlap in the diseases The paralytic disease can range from 1 leg or arm to they cause. paraplegia, quadriplegia, and even respiratory muscle 2) Rhinovirus causes the common cold and will be dysfunction. The later more serious events usually oc- discussed last. cur in persons older than 15 years. The affected extremities early in the course will have Polioi painful muscle spasms. Asymmetric muscle paralysis Poliovirus has the ability to infect cells in the: develops. Ultimately, atrophy and loss of reflexes occur (there are no sensory losses). 1) Peyers patches of the intestine. 2) Motor neurons. Vaccine This tropism explains: The inactivated polio vaccine, developed by Jonas 1) The fecal-oral mode of transmission. Salk, contains formalin-killed viruses that are in- 2) The disease paralytic poliomyelitis. jected subcutaneously, provoking an IgG antibody response that will protect against future viremia. This is Polio was one of the feared diseases of the 20th cen- used in Scandinavia today with excellent results. tury. In the 1950s 6 thousand cases of paralytic polio oc- The oral polio vaccine was developed by Albert B. curred each year in the U. S. Sabin and is currently used in the U. S. This vaccine This disease was in part due to improvements contains attenuated poliovirus that has lost the abil- in sanitation. Children tend to have fewer paralytic ity to multiply in the CNS. It is taken orally and repli- complications with poliovirus infection than do adults. cates and sheds in the feces in the normal fashion but As sanitation improved and fecally contaminated sub- does not cause paralytic poliomyelitis. stances were cleared, fewer people were exposed to po- This vaccine works by supplanting the wild type liovirus as children, and thus more adults were infected. (disease-causing) poliovirus with a docile attenuated The chances of developing paralytic poliomyelitis in- counterpart. We are NOT eliminating poliovirus com- creases as one gets older, thus explaining the increase in pletely but are only trying to eliminate the virulent paralytic poliomyelitis with improvements in sanitation. strain. In the case of the smallpox vaccine, immuniza- Now that a vaccine has been developed, the incidence tion of the population depleted the viral reservoir (hu- has markedly diminished. mans), and the virus was completely eliminated. The Disease Polio There are good and bad things about the oral Sabin vaccine, and there has been some debate stemming from The virus initially replicates in the tonsils and Peyers lawsuits and comparisons between our system and that patches, spreading to the blood, and across the blood- of Scandinavia. CNS barrier to the anterior horn of the spinal cord. Because of the initial replication in the tonsils, the Poiie virus can be spread by respiratory secretions, as well as 1) It is an oral vaccine. the usual fecal-oral route, early in the course of infection. 2) The oral route and full replication allow formation There are 3 disease manifestations: of both IgG in the blood and secretory IgA in the GI tract. 1) Mild illness: An asymptomatic infection or a mild 3) The attenuated virus is spread to contacts, re- febrile viral illness is the most common form. This es- sulting in a secondary infection and immunity in these pecially occurs in infants in less-developed nations, individuals. where the sanitation is poor. 2) Aseptic meningitis: Fever and meningismus can Negaie develop as the poliovirus infects the meninges. Recovery Vaccine-associated paralytic poliomyelitis: The is complete in 1 week. vaccine can pick up virulence and cause paralysis in the

21 7 CHAPTER 28. THE REST OF THE RNA VIRUSES

person taking the vaccine or in those exposed to shed- 1) Pleurodynia. Fever, headache, and severe lower ding (parents changing a vaccinated infant's diapers). thoracic pain on breathing (pleuritic pain) mark the Cox- This is very rare (1/2.6 million doses), but out of the 138 sackie B virus respiratory infection. cases of paralytic polio between 1973 and 1984, 105 2) MyocarditisIPericarditis. Infection and inflam- cases were considered vaccine related. Persons with im- mation of the heart muscle and pericardial membrane munodeficiency states should not receive the oral at- can result in self-limited chest pain or more serious ar- tenuated vaccine. rhythmias, cardiomyopathy, and heart failure. Many Ultimately, both vaccines have been very effective, viruses can cause this, but Coxsackie B is associated resulting in almost complete control of the virulent po- with 50% of the cases! liovirus in vaccinated geographic regions. Fig. 28-4. Comparisons of the enteroviruses.

Coxsackie A and B, Echoviruses, New VIRUSES THAT CAUSE THE "COLD" Enteroviruses Fig. 28-5. Rhino with the common cold, drinking a The remainder of the Enteroviruses in the Picor- Corona beer. This will help you remember that the rhi- naviridae family are responsible for a variety of dis- novirus and the coronaviridae both cause the com- eases. There is overlap since the different viruses can mon cold. cause the same clinical symptoms. The Coxsackie viruses (A and B), the echoviruses, and More than 100 different serotypes of rhinovirus are re- the new enteroviruses all have multiple serotypes and sponsible for the "common cold." Transmission occurs by all can cause: hand-to-hand spread of mucous membrane secretions. The coronaviridae cause a cold indistinguishable 1) Asymptomatic or mild febrile infections. from the rhinovirus common cold. About 15% of adult 2) Respiratory symptoms ("cold"). common colds are caused by the coronaviridae. 3) Rashes. 4) Aseptic meningitis: The enteroviruses are the most common cause of non-bacterial (aseptic) meningi- VIRUSES THAT CAUSE DIARRHEA tis in the U. S. Viruses that cause gastroenteritis are acquired by the fecal-oral route and usually prey on infants and young Coxsackie A children, although outbreaks among adults do occur. Coxsackie A can be differentiated from B by its effect Fever, vomiting, abdominal pain, and diarrhea follow a on mice. Coxsackie A causes paralysis and death of the 1-2 day incubation, and symptoms resolve within 4-7 days. mouse with extensive skeletal muscle necrosis. Cox- Infants die secondary to loss of fluids and electrolytes. sackie A also causes: DIARRHEA = DEATH BY DEHYDRATION Herpangina. A mild self-limiting illness characterized by fever, sore throat, and small red-based vesicles Two groups of viruses have been implicated in diar- over the back of the throat. rhea: calciviridae (including the Norwalk virus) and rotavirus. Coxsackie B Fig. 28-6. If your calico cat develops diarrhea, ro- Coxsackie B causes less severe infection in mice but tate the kitty litter frequently, or rotate the calico multiple organs can be damaged, such as heart, brain, cat off to Norway. This picture will help you remem- liver, pancreas, and skeletal muscle. It also causes: ber that viral gastroenteritis (diarrhea) is caused by

DISEASES Coxsackie ECHOvirus & A B New enterovirus Asymptomatic infections + + + Respiratory infections + + Rashes ("exanthems") + + + Aseptic meningitis + + + Herpangina + - - Pleurodynia - + - Myocarditis - + - Pericarditis - + + Figure 28-4 ILLNESSES CAUSED BY ENTEROVIRUSES

21 8 CHAPTER 28. THE REST OF THE RNA VIRUSES

from that of rotavirus, including diarrhea, vomiting, and fever. 2) Norwalk virus can occur in adults, but the virus is named after an outbreak in a Norwalk, Ohio, elementary school. In that episode, 50% of students developed diarrhea and severe vomiting. 3) Rotavirus is a member of the family reovirus (Respiratory Enteric Orphan). It is the number one cause of acute infectious diarrhea and a major cause of infant mortality worldwide. More than 1 million infant deaths per year are secondary to rotavirus. Note: Only bacterial cholera causes worse dehydration than the rotavirus. Treatment for all of these is supportive, with IV fluids and electrolytes. Oral rehydration therapy has revolutionized the treatment of diarrhea in underdeveloped nations, where IV fluids are a rare commodity.

RHABDOVIRIDAE AND RABIES Figure 28-5 Fig. 28-7. Rhabdoviruses have bullet-shaped, enveloped, helical symmetry nucleocapsids. caliciviridae, including the Norwalk virus, and the very common rotavirus. Rabies virus is the only virus in this family that normally infects humans. The rabies virus can infect all 1) Caliciviridae primarily infects young children warm-blooded animals, with dogs, cats, skunks, coyotes, and infants. The gastroenteritis is indistinguishable foxes, raccoons, and bats serving as reservoirs. The in-

Figure 28-6 CHAPTER 28. THE REST OF THE RNA VIRUSES fected creatures develop encephalitis and can become fear- less, aggressive, and disoriented. The famous stories of the mad farm dog or the wild wolf that stumbles fearlessly into an Alaskan town have popularized this conception. Fig. 28-8. When a human is bitten, the virus replicates locally at the wound site for a few days, then migrates (slowly over weeks to a year) up nerve axons to the central nervous system, causing a fatal encephalitis. Fig. 28-9. Brain cells in rabies demonstrate neuro- pathic changes and pathognomonic collections of virions in the cytoplasm called Negri bodies. Following the bite of a rabid animal there is an incu- Figure 28-8 bation period that has tremendous variability, ranging from a week to years! Once symptoms develop, there is rapid progression to death over 1-2 weeks: 2) When a person has been bitten or an open wound licked by a possibly rabid animal, the wound should be 1) Prodrome: Infected persons first develop nonspe- aggressively cleaned with soap and water. Washing cific symptoms of fever, headache, sore throat, fatigue, alone will significantly lower the risk of infection. nausea, and painfully sensitive nerves around the 3) The animal should be captured or destroyed. Cap- healed wound site. The muscles around the site may tured animals are confined, and if no symptoms develop even fasciculate! in the animal within 10 days, the animal does not have 2) Acute encephalitis: Hyperactivity and agitation rabies. If destroyed, the dead animal's brain can be ex- lead to confusion, meningismus, and even seizures. amined for Negri bodies or tested for uptake of fluores- Madness!! cently labeled antibodies to rabies virus. 3) Classic brainstem encephalitis: The brainstem 4) If the animal cannot be captured or the above tests infection causes cranial nerve dysfunction and painful are positive, the bitten individual should receive human contractions of pharyngeal muscles with swallowing liq- rabies immune globulin (passive immunization), fol- uids ("hydrophobia"). This results in an inability to lowed by 5 injections of the killed rabies virus vaccine swallow saliva and "foaming of the mouth." (active immunization). The idea is to develop immunity 4) Death ultimately occurs secondary to respiratory while the virus is still in the prolonged (variable length) center dysfunction. There has only been 1 reported case incubation period. of recovery from active rabies. Notice the similarities in the treatment of rabies with Through effective control and treatment strategies, that given to a person presenting with tetanus (see the number of actual cases of rabies has been dramati- Chapter 6). cally reduced. 1) Vaccination of dogs and cats has been very effective in the U. S., with only 18 cases reported from 1980 FILOVIRIDAE (Ebola and to 1993; infection was actually acquired in the U.S. in Marburg viruses) only 8 of these cases (Fishbein,1993). EBOLA VIRUS: April 4th, 1995: It was a summer morning in the city of Kikwit, Zaire ( population 400,000). A hospital laboratory technician had a fever and splitting headache with aching muscles and shoulders. He walked out of his home swinging his arms in loose circles, hoping to shake off the deepening pain. The feeling remained and a heavy fatigue and crampy abdominal pain soon settled in. Must be the flu, he thought. At work, he filled a cup with water and his hand, now sweaty, trembled as he brought the water to his lips. His throat hurt as he swallowed. He scarcely noticed the hiccups he suffered for the last half hour as his gut pain intensified. He stumbled to the rest room and had a large bowel movement. He staggered up and found Figure 28-7 the toilet water blood red. Slumping to the ground, he

220 CHAPTER 28. THE REST OF THE RNA VIRUSES

Figure 28-9 coughed and blood began to flow from his nose and infected body fluids. Reuse of unsterile needles was sig- mouth. His pants were soon soiled with bloody diarrhea. nificant in the Kikwit, Zaire epidemic. Physicians suspected this patient had a perforated Airbourne transmission is an unlikely mechanism in bowel and took him to surgery. Within 2 weeks of his humans but has been documented in monkeys. Current presentation, multiple hospital personnel became ill CDC guidelines do recommend use of masks and nega- with similar symptoms: fever (94%), diarrhea (80%), tive pressure room isolation as there is still some concern weakness (74%), dysphagia (41%), hiccups (15%), and over aerosol transfer during the later stages of illness. bleeding from mucous membranes--G.I. tract, vagina, and skin (38%). The disease affected men and women Control and Treatment: alike. (MMWR, June 30, 1995). By May 17, 93 persons Epidemics have been controlled by barrier precau- were infected and by June 25th, 296 persons. tions to avoid contact with infected body fluids, use of Suspecting that the deaths were secondary to a viral sterile needles, limiting laboratory blood work, and hemorrhagic fever (VHF)-like illness, seen in cases of Ebola and Marburg viruses, blood samples were sent proper disposal of corpses (sealed in leakproof material and cremated or buried in sealed casket). Laundry and to the CDC and polymerase chain reaction (PCR) and equipment must be incinerated, autoclaved, or washed enzyme-linked immunosorbent assay (ELISA) tests re- turned positive for Ebola virus. with bleach. There is no known effective anti-viral therapy. Ther- Fib, in filoviridae, means "filament" in Latin and de- apy is supportive. scribes the filamentous shape of the RNA viruses Ebola and Marburg that comprise the filovirus family. They Fig. 28-10. Summary of the "Rest of the RNA Viruses." are responsible for rare outbreaks of viral hemorrhagic fever in sub-Saharan Africa (Zaire, Sudan, Uganda, References Kenya) or in the U.S. or Europe following contact with CDC. Outbreak of Ebola viral hemorrhagic fever - Zaire 1995. monkeys from these sub-Saharan African areas. Hu- MMWR 1995;44(19)381-382. mans and monkeys are infected during outbreaks but it CDC. Update: outbreak of Ebola viral hemorrhagic fever - is not known what organism serves as reservoir be- Zaire, 1995. MMWR 1995;44(25):468-470. tween epidemics. Serologic studies have demonstrated CDC. Update: management of patients with suspected viral a 17% seropositivity for Ebola in selected central hemorrhagic fever - United States. MMWR 1995;44(25): African populations. This is highest in hunter-gatherers 475-479. such as the Aka Pygmies (37.5% seropositivity) who Duchin JS, et al. Hantavirus pulmonary syndrome: a clinical handle freshly killed animals. (Johnson, 1993). It is still description of 17 patients with a newly recognized disease. unclear what sets off the infrequent and deadly epi- N Engl J Med 1994;330:949-955. demics of viral hemorrhagic fever. Fishbein DB, Robinson LE. Current Concepts: Rabies. N Engl J Med 1993; 329:1632-1638. Transmission: Hantavirus pulmonary syndrome-United States, 1993. MMWR Morb Mortal Wkly Rep 1994;43:45-48. In the Zaire outbreak the most frequently infected Johnson ED, Gonzalez JP, Georges A. Filovirus activity groups were health care workers, home caregivers, and among selected ethnic groups inhabiting the tropical forest family members (especially spouses). All were in di- of equatorial Africa. Transactions of the Royal Society of rect contact with body fluids. Tropical Medicine and Hygiene 1993;87:536-538. Direct contact with blood, vomitus, urine, stool, or se- Peters CJ. Marburg and Ebola virus hemorrhagic fevers. In: men, from the living or dead patient, appears to be the Mandell GL, Bennett JE, Dolin R, eds. Principles and Prac- most important route of transmission. This likely occurs tice of Infectious Diseases; 4th edition. New York: Churchill via skin or mucous membrane contact with the virus- Livingstone, 1995;1543-1546.

22 1 Figure 28-10 THE REST OF THE RNA VIRUSES Figure 28-10 (continued) M. Gladin and B. Trattler, Clinical Microbiology Made Ridiculously Simple CMAedMaster CHAPTER 29. ANTI-VIRAL MEDICATIONS

Figure 29-1

The virus is a tough creature to kill. It has NO peptido- tive only against herpesviridae and has limited toxicity glycan wall, NO ribosomes, and NO cell membrane. All it to our cells. One of the herpesviridae, cytomegalovirus has is a protein coat, nucleic acid strand, and a few sim- (CMV), lacks thymidine kinase and so acyclovir is less ple enzymes. The only thing these critters do is replicate active for CMV infections. On the other hand, ganciclovir and then hang out in a latent state. The current antiviral is not dependent on a virus-specific thymidine kinase agents attack steps in viral replication much like the for phosphorylation. It kills ALL the herpesviridae in- chemotherapeutic agents attack replicating tumor cells. cluding CMV. It is also toxic to some rapidly replicating human cells such as neutrophils and platelets (causes Fig. 29-1. Site of action of antiviral drugs. neutropenia and thrombocytopenia). Two important concepts: Acyclovir 1) These drugs attack steps in actively replicating ("A cycle") viruses and have no effect on latent viruses. For this reason these drugs are only viirustatic (not virucidal). Fig. 29-2. To remember that ACYCLovir is used 2) Most of these drugs are nucleotide analogues. to treat infections caused by the herpes family, visual- They look just like the viral nucleotides but do not func- ize A CYCLE traversing the heights of a huge herpes tion appropriately. As such, they are taken up and used cold sore. by viral DNA polymerase or reverse transcriptase and are like monkey wrenches thrown into the gears of replication. They inhibit the DNA polymerase or reverse Clinical Uses transcriptase and are also incorporated into the grow- Studies demonstrate that if acyclovir is given very ing DNA strand, resulting in chain termination. early, it reduces the severity and duration of all herpes simplex and varicella-zoster (V-Z) infections, such as ANTI-HERPESVIRIDAE DRUGS cold sores (mucocutaneous herpes simplex infections), varicella (chickenpox), and zoster (shingles). However, Both acycloviir and ganciclovir are guanine ana- because these infections are self-limiting and mild, acy- logues that act against the herpes family. There is a key clovir is currently not recommended for these diseases. difference between them. To become active, acyclovir In the immunocompetent host, it is reserved for more must first be phosphorylated by a virus-specific thymi- serious infections such as herpes simplex encephalitis dine kinase. Most of the herpesviridae have this enzyme and herpes simplex and zoster infections of the eye. It is while human cells do not. For this reason acyclovir is ac- also approved for herpes simplex genital infections.

224 CHAPTER 29. ANTI-VIRAL MEDICATIONS

Figure 29-3 Figure 29-2 Adverse effects include reversible neutropenia and thrombocytopenia. Since zidovudine (AZT) also causes In the immunocompromised host, it is used for most neutropenia, carefully monitor neutrophil counts in pa- herpes infections (mucocutaneous, varicella, and zoster). tients taking both zidovudine and ganciclovir. Acyclovir is not used for CMV or Epstein-Barr virus infections. Foscarnet Fig. 29.3. Adverse effects are minimal. With high intravenous doses acyclovir (A CYCLE) may crystallize in This pyrophosphate analogue inhibits DNA poly- the renal tubules, resulting in reversible renal toxicity. merase and reverse transcriptase. It has extended About 19 of patients have CNS side effects, such as con- anti-viral activity, covering the herpesviridae and HIV. fusion or seizures. It is important to stress that this anti-viral activity against HIV is very minimal and not adequate for treat- Famciclovir and Valacyclovir ment or viral suppression. Foscarnet is used for AIDS patients with: These 2 new drugs have the same mechanism of action as acyclovir but have the added punch of increased 1) CMV retinitis. drug levels after oral absorption. One study (Tyring, 2) Acyclovir-resistant strains of herpesviridae. 1995) compared famciclovir with placebo in the treatment of adults with herpes zoster and found that it re- A big side effect, especially in AIDS patients, is reduced the time to lesion healing, viral shedding, and, versible nephrotoxicity. Increased seizure potential is more importantly, the duration of post-herpetic neural- possible in patients with prior history of seizure, head gia by almost 2 months! trauma, renal impairment or taking concomitant med- These drugs are currently indicated only for herpes ications that increase seizure potential. zoster and recurrent genital herpes in immunocompetent adults. Adverse effects are mild and include headache, nausea, diarrhea, and dizziness. THE HUMAN IMMUNODEFICIENCY VIRUS (HIV) Ganciclovir ("Gang of cycles") There has been an explosive development of new antiretroviral medications. "Have a HAART (Highly Active Fig. 29-4. A GANG OF CYCLES running over AntiRetroviral Therapy)" is the foremost theme for those HSV, V-Z-V, CMV, EBV, and Mr. Neutrophil and Mrs. physicians caring for HIV positive patients. HAART Platelet. GANCICLovir has broader coverage of the refers to the use of several very potent anti-HIV (A.K.A. herpesviridae than acyclovir, but it is more toxic. antiretroviral) agents in combination to suppress viral replication and stop the spread of resistant viruses. Clinical Uses There are at least 14 different anti-HIV medications in Because of its toxicity ganciclovir is only used for the United States: six nucleoside reverse transcriptase CMV infections in immunocompromised hosts: inhibitors f zidovudine (AZT, ZDV), didanosine (ddl), zalcitabine (ddC), stavudine (d4T), lamivudine (3TC) and 1) AIDS patients: CMV retinitis, pneumonitis, abacavirl; three non-nucleoside reverse transcriptase in- esophagitis. hibitors (nevirapine, delaviridine and efavirenz); and 2) Bone marrow transplant patients: CMV pneu- five protease inhibitors (saquinavir, indinavir, ritonavir, monitis and prophylaxis against CMV infection. nelfinavir and amprenavir).

225 CHAPTER 29. ANTI-VIRAL MEDICATIONS

Figure 29-4

Before representing each of these drugs, lets focus on the big picture of how to use them. 1. Antiretroviral therapy should be started for most patients with advanced HIV infection. If their CD4 count is high and their viral burden (plasma HIV RNA level) is very low, treatment can be delayed. I 2. Three or four drugs should be used because the CDC r-HELPER CELL data shows these combinations are more effective and prevent emergence of resistance. Choice of agents can be tailored to avoid side effects. The classic principle behind HAART is the use of several different agents with varying mechanisms of antiviral activity and patterns of resistance. A three drug combination of two nucleoside reverse transcriptase inhibitors and a protease inhibitor is the 1st line standard RED BLOOD CELL REUTR WHIL of care. Side effects or drug interactions caused by pro- GRANULOCYTE tease inhibitors decrease their appeal in some patients. Therefore, "protease-sparing" regimens have been de- Figure 29-5 signed. These alternative regimens consist of two nucleoside analogs and a non-nucleoside analog. Tailoring tions-cost. Protease inhibitor com binations cost anti-HIV medications requires patience while finding $10,000 to $20,000 a year! (Zuger, 1996). the right mix of efficacy and tolerability. Specific examples of these combinations are shown below. NUCLEOSIDE REVERSE Three-drug combinations: TRANSCRIPTASE INHIBITORS (NRTIs) zidovudine + lamivudine + protease inhibitor stavudine + lamivudine + protease inhibitor Zidovudine (ZDV or AZT) stavudine + didanosine + protease inhibitor This is the first-line anti-HIV medication. Large stud- Protease-sparing combinations ies have shown that zidovudine: zidovudine + didanosine + nevirapine zidovudine + didanosine + efavirenz 1) Reduces mortality and opportunistic infec- 3. Physicians must follow CD4 T-lymphocyte counts, tions in symptomatic HIV-infected patients with CD4 viral load assays, and the patients clinical status to de- T-lymphocyte counts less than 200/mm 3 (Fischl, 1987). termine if treatments are effective. If CD4 counts drop, 2) Delays progression to AIDS in HIV infected pa- viral load increases, or opportunistic diseases develop, tients with CD4 T-lymphocyte counts less than 500/mm 3 therapy should be changed. If side effects develop, drugs (Volberding, 1990; Fischl, 1990). should likewise be changed. The problem with zidovudine is that HIV can rapidly There will be many more trials in the following years develop resistance to zidovudine when it is used alone. with the goal of completely suppressing viral load. HIV This is the rationale for always starting with 2 agents. may become a virus we harbor in a suppressed state and 3) Reduces maternal-to-infant transmission of AIDS may be prevented indefinitely. A new problem is HN when given to the mother orally prior to birth, in- already emerging, especially for less developed na- travenously during delivery, and then to the baby orally

226 CHAPTER 29. ANTI-VIRAL MEDICATIONS

for 6 weeks. In a recent study, this regimen reduced the Stavudine (d4T) transmission rate from 25% to 8% (Conner, 1994)! Mild increases of hepatic transaminases have also Fig. 29-5. AIDS knocks out CD4 T-lymphocytes, and been noted during treatment with stavudine. AZT (ZDV) knocks out red blood cells (anemia) and neutrophils (neutropenia). Abacavir It also causes, other pesky adverse effects including headache, insomnia, myalgias, nausea, and CNS dis- This synthetic carbocyclic NRTI is the newest agent turbances (confusion, seizures). If a patient develops in this class. Hypersensitivity reactions have been the these problems, the dose can be decreased or another most concerning adverse effect, reported in approxi- anti-HIV drug can be used. mately 5% of patients receiving abacavir. A rash is accompanied by systemic signs and symptoms such as Didanosine (ddl), Zalcitabine (ddC), fever, fatigue, nausea, vomiting, diarrhea or abdominal Stavudine (d4T), and Lamivudine (3TC) pain. These symptoms occur early and usually appear within the first 6 six weeks of treatment. Symptoms These nucleoside reverse transcriptase inhibitors are usually resolve rapidly after discontinuation of the proving effective in reducing viral RNA load, increasing drug. It is important too remember that once abacavir CD4 counts, and slowing progression to AIDS. When has been discontinued because of a hypersensitivity re- added to zidovudine, they prevent the emergence of zi- action, it should not be reintroduced. More severe out- dovudine resistance. The combination of zidovudine and comes, including death, have been reported to occur lamivudine (3TC) has been particularly effective and is when abacavir was reinstituted. considered the first line of therapy when combined with a protease inhibitor or non-nucleoside reverse tran- Non-specific side effects: All of these agents can scriptase inhibitor. In fact, zidovudine and lamivudine cause rash, fatigue, headaches, nausea, vomiting, diar- are now available in a combination product, Combivir. rhea, abdominal pain, and insomnia. Physicians may Combination products will likely be a trend for future need to juggle these medications to find the best agent treatment of HIV because it decreases the number of with the least side effects. tablets that patients are required to take (A.K.A. pill- burden) and increases compliance with therapy. Peripheral Neuropathy ("Remember that the Ds cause peripheral Lamivudine (3TC) neuropathies") Lamivudine is generally well tolerated. No dose-limit- The major toxic effect associated with didanosine ing toxic effects have been reported. In addition to the (ddl), zalcitabine (ddC) and stavudine (d4T) is periph- treatment of HIV, lamivudine plays a very important role eral neuropathy. Peripheral neuropathy usually mani- in the treatment of hepatitis B virus (HBV) as monother- fests with numbness or tingling of the feet, seems to be apy and in combination with interferon (IFN) alpha. dose related, and is generally reversible with discontin- Lamivudine potently inhibits hepatitis B viral DNA uation of these agents. Pre-existing neuropathy or con- replication and has a very favorable side effect profile. comitant use of neurotoxic medications increases the Didanosine (ddl) likelihood of developing neuropathy. Therefore, you do not want to use these agents in combination. This is a synthetic purine nucleoside analogue that is unstable in acid conditions, such as the gastric environ- Non-Nucleoside Reverse Transcriptase ment. Therefore, it is formulated with a buffer or Inhibitors (NNRTIs) antacids, and should be taken on an empty stomach. Didanosine can cause pancreatitis which may be life NNRTIs bind directly and noncompetitively to the en- threatening, in which case the drug should be dis- zyme reverse transcriptase. They block DNA polymerase continued. Other risk factors for pancreatitis, such as his- activity by causing conformational change and disrupting tory of pancreatitis, alcoholism, and hypertriglyceridemia, the catalytic site of the enzyme. Unlike nucleoside ana- may increase the likelihood of developing pancreatitis. logues, NNRTls do not need phosphorylation to become active, and they are not incorporated into viral DNA. When Zalcitabine (ddC) NNRTIs are administered as a single agent or as part of an inadequately suppressive treatment regimen, resistance Unlike didanosine, zalcitabine is well absorbed from emerges rapidly. Mutations conferring resistance to one the gastrointestinal tract. Pancreatitis occurs less com- drug in this class generally confer cross-resistance to most monly than with didanosine. Severe oral ulcers have other NNRTIs. Cross-resistance to nucleoside analogues been reported in up to 3% of zalcitabine-treated patients. or protease inhibitors has not been observed.

22 7 CHAPTER 29. ANTI-VIRAL MEDICATIONS

Nevirapine All the PIs have navir at the end of their names. Think of the PIs causing a viral nadir or No virus. Nevirapine was the first NNRTI to be approved for treating HIV infection. Nevirapine is an inducer of the Saquinavir cytochrome P450 CYP3A system, including autoinduc- tion of its own metabolism. Because of this induction po- Saquinavir was the first PI to be approved by the tential, nevirapine is avoided in combination with other FDA. The biggest problem with saquinavir has been medications that are metabolized through the CYP450 that a minimal amount of the drug gets absorbed when system, especially antiviral medications. taken orally. Fortovase is a soft gel formulation of saquinavir with Delaviridine enhanced bioavailability that has replaced hard gel saquinavir, Invirase. Fortovase should be taken with a Delaviridine is metabolized by the cytochrome P450 meal to increase oral absorption. The main side effects system and also inhibits CYP450 activity, including its are as you might have guessed, gastrointestinal. These own metabolism. This inhibition may lead to increase effects include diarrhea, nausea, abdominal discomfort plasma levels of concurrent medications metabolized and pain, dyspepsia and vomiting. through CYP450. Efavirenz Indinavir Efavirenz is the newest NNRTI to be approved by the Indinavir is the opposite of saquinavir because it is FDA. Central Nervous symptoms have been reported in rapidly absorbed in a fasting state. If indinavir is approximately 50% of patients treated with efavirenz. given with a high-fat/high-protein meal, absorption is These symptoms include abnormal dreams that are of- substantially reduced. Consumption of a light meal ten dysphoric in nature as well as insomnia, dizziness, (e.g. dry toast and coffee) has minimal effect on ab- impaired concentration, and somnolence. Symptoms sorption. The main side effects again are gastro- tend to diminish with continued therapy but may in- intestinal including abdominal pain, nausea, vomiting crease with concomitant alcohol and psychoactive drug and diarrhea. Nephrolithiasis or "kidney stones" occa- use. You may have to stop this drug if your patient starts sionally occur with renal insufficiency or acute renal dreaming about axe-wielding Elves (Efavirenz). failure. Therefore caution is needed in patients with In vitro studies have shown that efavirenz has in- compromised kidney function. All patients receiving hibitory effect on the CYP450 system. This may lead to indinavir should drink at least 1.5L (48 oz.) of water drug interactions similar to those with delaviridine. daily to ensure adequate hydration and prevent development of kidney stones. Rash Ritonavir Rash is a frequently reported adverse effect associated with nevirapine, delaviridine and efavirenz occur- Ritonavir is the most poorly tolerated of the four cur- ring in 17%, 18% and 27% of patients in phase 111111 rently available PIs. The most corn only reported side trials respectively (Zalalem, 1999). The rashes were effects are gastrointestinal, including nausea, vomiting, usually mild to moderate and usually occurred within diarrhea and abdominal pain. the first 4 weeks of treatment. The rash resolved with discontinuation of the drug. Severe rashes including ul- Nelfinavir cerations and Stevens-Johnson syndrome (SJS) have also been reported. The most frequently reported side effect associated with nelfinavir is diarrhea, noted in up to 32% of patients. Nelfinavir-associated diarrhea is generally mild PROTEASE INHIBITORS (PIs) to moderate. Other reported side effects include nausea, vomiting, abdominal pain, and rash. HIV protease is required for production of infectious HIV particles. Protease inhibitors inhibit this vital enzyme. Amprenavir There are currently 5 protease inhibitors: saquinavir, ritonavir, indinavir, nelfinavir and amprenavir. Amprenavir is the latest PI to be approved by the Triple therapy with ZDV, ddC, and the protease in- FDA. The most frequently reported side effects are gas- hibitor saquinavir, resulted in greater and longer lasting trointestinal (nausea, vomiting, diarrhea and abdomi- elevations of CD4-T cell counts and greater reductions in nal pain); most are graded as mild to moderate. Other viral levels than 2-drug therapy. Side effects were simi- reported side effects include rash, parasthesias, and de- lar for 3 and 2 drug regimens (Collier 1996). pressive or mood disorders.

228 CHAPTER 29. ANTI-VIRAL MEDICATIONS

Interleukin-2 infusion Interleukin-2 is a cytokine released by T-lymphocytes that regulates the proliferation of CD4 (helper-T) T-lymphocytes. In a recent clinical trial HIV infected patients with CD4 counts greater that 200 cells/cc were treated with infusions of interleukin-2. The treatment resulted in a dramatic rise in CD4 counts from a mean of 400 cells/cc to 900 cells/cc! There was no increase or decrease in the viral RNA load associated with this elevation of CD4 counts to a normal level. Whether this will translate into an improved clinical outcome remains to be determined (Kovacs, 1996.) Post-Exposure (i.e., Needle Stick) HIV Prophylaxis Figure 29-6 After a needle-stick or other percutaneous exposure with HIV-infected blood the risk of seroconversion is Rimantadine appears to be as effective as amanta- 0.3%. This risk goes up if the injury is deep, the needle dine for the prevention of influenza A. It has less CNS was in the patients vein or artery, the needle had visible side effects (anxiety and confusion) and does not require blood on it, or the patient died within 60 days of the stick dose adjustments in renal failure, making it a safer (suggesting late-stage AIDS with high levels of viremia). agent for the elderly. Treatment after an exposure with zidovudine (ZDV), has been shown in a case-control study to reduce the risk Neuraminidase Inhibitors of seroconversion by 79%. ZDV + lamivudine (3TC) is More recently a new class of agents, neuraminidase more active against ZDV resistant strains of HIV and the inhibitors, with clinical activity against both influenza protease inhibitors further increase HIV killing. So the A and B types have been introduced. These agents tar- public health service has now recommended that exposed get neuraminidase (see Page 173), which is responsible health workers at highest risk receive triple therapy with for cleaving the bonds between emerging virus and the ZDV, 3TC, and indinavir for 4 weeks. Lower risk expo- cell and therefore freeing the virus to penetrate respi- sures should receive ZDV and 3TC (MMWR, 1999). ratory secretions and replicate. Resistance to neuraminidase inhibitors appears to be slow developing. MISCELLANEOUS These agents are indicated for the treatment of uncom- plicated acute illness due to influenza and will decrease ANTI-VIRAL AGENTS flu-symptoms by 1 to 2 days. Amantadine Oseltamivir ("A Man to Dine") Oseltamivir is available as an oral tablet, which must Amantadine has the narrowest spectrum, only in- be started within 2 days of onset of influenza symptoms. hibiting Influenza A, NOT B; the "A" is for "Amanta- Oseltamivir is the only neuraminidase inhibitor used dine." It is thought to do this by inhibiting viral genome for flu prophylaxis as well. This agent is relatively well uncoating in the host cell. It has minimal side effects. tolerated with dizziness, headache, fatigue, insomnia and vertigo being the most frequent side effects occur- Fig. 29-6. Amantadine. You have a hot dinner date ring in less than 2% of patients. with this stud of A MAN. You meet him TO DINE at a fancy restaurant in town; he sits at the table and takes Zanamavir off his coat (uncoats). To your intense chagrin, he then begins to blow his nose loudly and drip strings of snot Zanamavir is available as an intranasal spray and on his plate, explaining that he has a terrible flu. oral inhaler and should be initiated within 2 days of onset of influenza symptoms. Of course, because this drug If given early during an influenza A infection, aman- is delivered through the upper respiratory tract, it is not tadine will decrease the duration of flu symptoms. It recommended in patients with severe chronic obstruc- also helps prevent influenza A if given prophylactically. tive pulmonary disease (COPD), or asthma. Nose bleed For example, it can be given to nursing home residents is the most characteristic side effect occurring with the if there is an outbreak of influenza A. nasal spray in up to 4% of patients.

229 CHAPTER 29. ANTI-VIRAL MEDICATIONS

Ribavirin Danner SA, et al. A short-term study of the safety, pharmacokinetics, and efficacy of ritonavir, an inhibitor of HIV-1 pro- Ribavirin has a wide spectrum of activity against tease. N Engl J Med 1995;333:1528-33. many DNA and RNA viruses. However it is teratogenic Fischl MA, et al. AIDS Clinical Trials Group: The safety and in small mammals. Due to concerns about safety, it is efficacy of zidovudine (AZT) in the treatment of subjects only used for severe respiratory syncytial virus (RSV) in- with mildly symptomatic human immunodeficiency virus fections in infants, for the rare case of Lassa fever (a se- type 1 (HIV) infection: a double-blind, placebo-controlled trial. Ann Intern Med 112:727-737,1990. vere influenza-like illness in Africa caused by the Lassa Fischl MA, et al. AZT Collaborative Working Group: The fever virus, in the family Arenaviridae), and for the han- efficacy of azidothymidine (AZT) in the treatment of tavirus pulmonary syndrome (investigational use). patients with AIDS and AIDS-related complex: a double- blind, placebo-controlled trial. N Engl J Med 317:185- 191,1987. Interferon Keating MR. Antiviral Agents for Non-Human Immunodefi- (alpha, beta, gamma) ciency Virus Infections. Symposium on Antimicrobial Agents-Parts XV. Mayo Clin Proc 74:1266-83, 1999. Human interferons are cytokines that promote a cel- Kinchington D. Recent advances in antiviral therapy. J. Clin. lular anti-viral state. They have been produced in large Pathol. 52:89-94, 1999. quantities by using recombinant DNA technology. Kovacs JA, Vogel S, Albert JM, et al. Controlled trial of inter- Many studies are looking at these agents for the treat- leukin-2 infusions in patients infected with the human im- ment of viral infections as well as cancers. munodeficiency virus. N Engl J Med 1996;335:1350-6. Interferon alpha has been used to treat hepatitis C Markowitz M, et al. A preliminary study of ritonavir, an in- and B infection (chronic active or persistent hepati- hibitor of HIV-1 protease, to treat HN-1 infections. N. Engl. J. Med. 1995; 333:1534-9. tis). Treatment results in a suppression of the virus Sande MA, et al. Antiretroviral therapy for adult HIV-infected and clinical remission. Unfortunately, when the inter- patients; recommendations from a state-of-the-art confer- feron is discontinued, more than half of patients will ence. JAMA 1993;270:2583-2589. have a relapse (50% for hepatitis B and 75-80% for Sanford JP, Gilbert DN, et al. Guide to Antimicrobial Therapy hepatitis C)! 1996. Antimicrobial Therapy, Inc, Dallas, Texas; 1996. Ribavirin has also been used in oral form to treat Skowron G, et al. Alternating and Intermittent Regimens of hepatitis C virus (HCV) in combination with Interferon Zidovudine and Dideoxycytidine in Patients with AIDS or (IFN) and as monotherapy. While ribavirin monother- AIDS-Related Complex. Ann Intern Med 118:321-329,1993. apy is successful at decreasing elevated liver enzymes Treanor JJ, Hayden FG, Vrooman PS, et al. Efficacy and Safety it does not eradicate virus levels in the blood and there- of the Oral Neuraminidase Inhibitor Oseltamivir in treating fore does not appear to be the answer. However, combi- Acute Influenza: a randomized controlled trial. JAMA 283: 1016-1024,2000. nation therapy has been shown to improve response Tyring S, et al. Famciclovir for the treatment of acute herpes rates and to minimize drug resistance and appears to zoster: effects on acute disease and postherpetic neuralgia. be the most promising means of treating chronic he- Ann Int Med 1995;123:89-96. patitis C to date. Update: Provisional Public Health Service Guidelines for the Use of Antiretroviral Agents in HIV-Infected Adults and Fig. 29-7. Summary of anti-viral drugs. All of these Adolescents MMWR 1999; 1-47. medications have different side effects and have to be jug- Volberding PA, et al. AIDS Clinical Trials Group of the Na- tional Institute of Allergy and Infectious Diseases: Zidovu- gled around to find the combination with the least adverse dine in asymptomatic human immunodeficiency virus efects and greatest sustained depression of viral load. infection: a controlled trial in persons with fewer than 500 CD4-positive cells per cubic millimeter. N Engl J Med References 322:941-9,1990. Wenzel RP. Expanding the Treatment Options for Influenza. Balfour HH. Antiviral Drugs. N Engl J Med 340:1255-68, JAMA 283:1057-59, 2000. 1999. Wong DKH, et al. Effect of Alpha-Interferon Treatment in Pa- Collier AC, et al. Treatment of HIV infection with saquinavir, tients with Hepatitis B e Antigen-Positive Chronic Hepati- zidovudine, and zalcitabine. N Engl J Med 1996;334: tis B: A Meta-Analysis. Ann Int Med 119:312-323;1993. 1011-7. Zelalem T, Wright AJ. Antiretrovirals. Symposium on An Conne EM, et al. Reduction of maternal-infant transmission timicrobial Agents. Mayo Clin Proc 74:1284-1301, 1999. of human immunodeficiency virus type 1 with zidovudine Zuger A. Treating HIV infection: New developments. Journal treatment. N Engl J Med 331:1173-80, 1994. Watch 1996; 16:141-2.

230 Figure 29-7 ANTI-VIRAL DRUGS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple pMedMaster Figure 29-7 (Continued) M. Gladwin and a Trattler, Clinical Microbiology Made Ridiculously Simp/eMAedMaster Figure 29-7 (Continued) M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple OMedMaster CHAPTER 30. PROTOZOA

PART 4. PARASITES

CHAPTER 30. PROTOZOA

Protozoa are free-living, single celled, eucaryotic cells eating bacteria, other protozoa, and even human in- with a cytoplasmic membrane and cellular organelles, testinal and red blood cells. This trophozoite can convert including 1 or 2 nuclei, mitochondria, food vacuoles, and to a precyst form, with two nuclei, that matures into a endoplasmic reticulum. They come in many sizes, from tetranucleated cyst as it travels down and out the colon. 5 micrometers to 2 millimeters. They have an outer The precyst contains aggregates of ribosomes, called layer of cytoplasm (ectoplasm) and an inner layer (en- chromotoid bodies, as well as food vacuoles that are doplasm), which appear different from each other under extruded as the cell shrinks to the mature cyst; it is the the microscope. mature cyst that is eaten, infecting others. The protozoa ingest solid pieces of food through a Sometimes (10% of infected individuals) the tropho- small mouth called the cytostome. For example, amoe- zoites invade the intestinal mucosa causing erosions. bas (Entamoeba histolitica) can ingest human red blood This results in abdominal pain, a couple of loose stools cells into their cytoplasm. The protozoa reproduce asex- a day, and flecks of blood and mucus in the stool. The in- ually, undergoing DNA replication followed by division fection may become severe, with bloody, voluminous di- into 2 cells. They also reproduce sexually by the fusion arrhea. of 2 cells, followed by the exchange of DNA and separa- The trophozoites may penetrate the portal blood cir- tion into 2 cells again. culation, forming abscesses in the liver, followed by When exposed to new environments (such as temper- spread through the diaphragm into the lung. Here the ature changes, transit down the intestinal tract, or trophozoite infection causes pulmonary abscesses and chemical agents), the protozoa can secrete a protective often death (worldwide: 100,000 deaths annually). coat and shrink into a round armored form, called the The stool is examined for the presence of cysts or cyst. It is this cyst form that is infective when ingested trophozoites. Trophozoites with red blood cells in the by humans. Following ingestion it converts back into cytoplasm suggest active disease, while cysts or tropho- the motile form, called the trophozoite. zoites without internalized red cells suggest asympto- THE INTESTINAL PROTOZOA matic carriage. CAT scan or ultrasound imaging of the liver will reveal abscesses if present. There are 5 intestinal protozoa that cause diarrhea. Prevention rests on good sanitation: proper disposal Entamoeba histolytica causes a bloody diarrhea, and Gi- of sewage and purification (boiling) of water. ardia lamblia and Cyclospora cayetanensis cause a Fig. 30-2. The non-bloody diarrhea. Both occur in normal individuals. Metro (metronidazole) runs over Cryptosporidium and Isospora belli cause severe diar- Entamoeba histolytica, Giardia lamblia, Trichomonas vaginalis, and the anaerobic cocci and bacilli including rhea in individuals with defective immune systems Bacteroides fragilis, Clostridium difficile and Gard- (such as patients with AIDS). vaginalis. nerella This drug is also called Flagyl (its Entamoeba histolytica trade name) because it kills the flagellated bugs, Giar- dia and Trichomonas. This organism is the classic amoeba we have all heard about. It moves by extending creeping projec- Adverse effects of metronidazole tions of cytoplasm, called pseudopodia (false feet). The pseudopodia pull it along or surround food particles. There is no drinking allowed on the train because it About 10% of the world population and 1-5% of the U. travels rapidly and jarringly, causing stomach upset to S. population are infected with Entamoeba histolytica. passengers that consume alcohol (Antabuse-disulfiram Most of these infections are asymptomatic, as the amoe- effect). If you eat the train, as King Kong once attempted, bas live in peace inside their host carriers. These carri- you would end up with a metallic taste in your mouth. ers pass the infective form, the cyst, to other individuals by way of the fecal-oral route. It is noteworthy that ho- Giardia lamblia mosexual men commonly are asymptomatic carriers. Fig. 30-1. Giardia lamblia exists in 2 forms: as a cyst Fig. 30-1. The motile feeding form of the amoeba is and as a mature, motile trophozoite that looks like a the trophozoite, which cruises along the intestinal wall kite.

234 CHAPTER 30. PROTOZOA

Figure 30-1

I i eiaed ha 5% f U.S. ad hab hi - 25% f Aeica h egic eidece f ei gai, aaica. Obea cc ifeci. I ca cae bea f diahea f he eage caiae diig ae. The ga- caiaed icia ae ce ad i ifa i i a habed b a de ad beae; i da cae cee. Sadic cae ca cc i cae fee dee Giardia lamblia ifeci aee. afe diig f "cea" ai ea. Crptosporidiam i igeed a a d c ha Afe igei f he c, Giardia lamblia ce cai 4 ie ie. I ife cce cc he hie f ad cie d ad adhee ihi he ieia eiheia ce, ad i cae di- he a ieia a. The gai ca he ahea ad abdia ai. Thee ae ef- a ieie, iefeig ih ieia fa ab- i iig i icee idiida. Hee, i. The ae heefe aced ih fa, hich ha i icied aie (AIDS aie, ca- a horrific odor! The aie i hae a gea, fh ce aie, ga aa eciie h ae diahea, ag ih abdia ga diei ad eceiig ieie hea), hi gai ca. Sice Giardia d NOT iade he ieia cae a eee, aced diahea ha i ife- a, hee i NO bd i he !!! heaeig. Thee aie a hae 3-17 ie f For diagnosis and control of Giardia: e da. Ce, hee i effecie hea. A e 1) Eaiai f f c hie. acide dg, aithromcin (ee Chae 17), i be- 2) Commercial immunoassay kit to detect Giardia ig died. lamblia aige i ae eac f ecie. 3) Saiai eae. Tea hee aie ih metronidaole (see Fig. Isospora and Microsporidia 30-2). These organisms cause a severe diarrhea in immunocompromised individuals. They are transmitted via the Cryptosporidium fecal-oral route. Fortunately, the combination of trimethoprim with sulfamethoxazole (see Chapter I i aae ha hi cie i eehee! 19) is effective against Isospora, while albendazole Aia ad ha ae ea ifeced ad ab (see Chapter 31) can treat Microsporidia.

235 CHAPTER 30. PROTOZOA

Figure 30-2 THE SEXUALLY TRANSMITTED find a thin, watery, frothy, malodorous discharge in the PROTOZOAN vaginal vault. Males are usually asymptomatic. Diagnosis of Ticha: Ticha agiai 1) Microscopic examination of vaginal discharge on a Fig. 30-3. Ticha agiai is transmitted sex- wet mount preparation will reveal this highly motile ually and hangs out in the female vagina and male ure- parasite. thra. The trophozoite of Ticha agiai is a 2) Examination of urine may also reveal Tri- flagellated protozoon (as is Giadia abia). cha agiai. A female patient with this infection may complain of Treat your patient with metronidazole (see Fig. 30- itching (pruritus), burning on urination, and copious 2). Provide enough for sexual partners. Even though vaginal secretions. On speculum examination you will males are usually asymptomatic, they must be treated

236 CHAPTER 30. PROTOZOA

Figure 30-3

or the female partner will be reinfected (since this or- and microscopic examination may show the motile ganism is not invasive, no immunity is acquired). amoeba. Two patients who survived were treated with in- THE FREE-L WING MENINGITIS- trathecal amphotericin B, an antifungal agent. CAUSING AMOEBAS Acanthamoeba Both Naegeia fei and Acahaeba are free- living amoeba that live in fresh water and moist soils. Acahaeba is responsible for a chronic, granulo- Infection often occurs during the summer months when matous, brain infection in immunocompromised pa- people swim in freshwater lakes and swimming pools tients, such as those with AIDS. Over a period of weeks, that harbor these organisms. Although large numbers they will develop headache, fever, seizures, and focal of persons are exposed, actual infection rarely occurs. neurologic signs. Examination of the CSF and brain tis- When it does, the organisms penetrate the nasal mu- sue will reveal Acahaeba in both the cyst stage and cosa, through the cribriform plate, into the brain and trophozoite stage. Treatment is difficult and involves spinal fluid. Both amoeba can cause an infection of the multiple antifungal drugs with pentamidine. meninges and brain (meningoencephalitis). Naegeia This organism may also infect the cornea (in im- fei will cause a sudden deadly infection in immuno- munocompetent persons), often when contact lenses are competent persons, while Acahaeba will cause a not properly cleaned. This corneal infection (keratitis) slow granulomatous infection, usually in immunocom- can lead to blindness. Treatment is with antimicrobial promised persons. eye drops. Fig. 30-5. Comparison of Naegleria and Acan- Naegleria fowleri thamoeba infection. Fig. 30-4. Naegeia fowleri is known for FOWL PLAY, since 95% of patients will die within 1 week. In- THE MAJOR PROTOZOAN fected persons will present with a fever, headache, stiff INFECTIONS IN AIDS PATIENTS neck, nausea, and vomiting, which is very similar to a bacterial meningitis. If asked, they will give a history of The ineffective immune system in AIDS patients sets swimming a week earlier. Examination of cerebrospinal them up for certain infections that seldom affect the im- fluid (CSF) reveals a high neutrophil count, low glucose, munocompetent host. We have already discussed 2 par- and high protein, exactly like a bacterial meningitis!!! asites that can establish a severe, chronic diarrhea in The Gram stain and culture will reveal NO bacteria, AIDS patients: Cidi and Ia. T

J 237 CHAPTER 30. PROTOZOA

Figure 30-4

Naegleria Acanthamoeba ACUTE meningoencephalitis in normal CHRONIC meningoencephalitis in hosts immunocompromised hosts Mature amoeba only in brain tissue Cysts and mature amoeba found in (NO cysts) brain tissue No corneal infection Corneal infection: diagnose by corneal scraping Figure 30-5 THE AMOEBAS other parasites found more commonly in AIDS patients household cat feces. Kitty litter boxes are the most com- than in the general population are Toxoplasma gondii mon source of exposure for humans, as up to 80% of cats and Pneumocystis carinii. These protozoa are harbored are infected in the United States. Toxoplasma gondii by most persons without problems. In AIDS, when the undergoes sexual division in the cat and is excreted in T-helper cell count drops below 200, these bugs flourish the feces as the infectious cyst. and cause disease. The protozoan causes disease by reactivation of a latent infection in an immunocompromised person or as a Tooplasma gondii primary infection in a pregnant woman (leading to transplacental infection of the fetus). Many animals are infected with Toxoplasma, and humans are infected by the ingestion of cysts in under- 1) Immunocompromised patients with AIDS or those cooked meats (raw pork) or food contaminated with who are taking immunosuppressive drugs (for cancer or

238 CHAPTER 30. PROTOZOA

organ transplantation) are susceptible to growth of the Pnemoci cainii latent Taa gdii. The infection can present in many ways-with fever; lymph node, liver, and spleen Peci caiii is a flying-saucer appearing enlargement; pneumonia; or frequently with infection of FUNGUS that has previously been classified as a proto- the meninges or brain. In fact, Taa encephalitis zoan but now has been shown to be more closely related is the most common central nervous system infection to fungi. This organism appears to invade the lungs of all in AIDS patients. The brain infection can involve a individuals at an early age and persists in a latent state. growing mass, much like a tumor, with symptoms of In fact, based on IgM and IgG levels, it appears that headache and focal neurologic signs (seizures, gait in- about 85% of children have had a mild or asymptomatic stability, weakness, or sensory losses). Infection of the respiratory illness with Peci caiii by age 4. In retina, chorioretinitis, is also common, resulting in vi- persons with a functioning immune system, this organ- sual loss. Examination of the retina reveals yellow- ism will live comfortably within the lung without caus- white, fluffy (like cotton) patches that stand out from ing symptoms. However, in immunocompromised pa- the surrounding red retina. tients (AIDS patients, cancer patients, and organ trans- 2) Taa is one of the transplacentally ac- plant recipients), this organism can multiply in the quired TORCHES organisms that can cross the blood- lungs and cause a severe interstitial pneumonia, called placenta barrier (see Fig. 26-2.). Transplacental fe- Pneumocystis carinii pneumonia (PCP). tal infection can occur if a pregnant woman who has PCP is the most common opportunistic infection of never been previously exposed to Taa gdii AIDS patients. Without prophylactic treatment there is is infected. Congenital toxoplasmosis does not occur a 15% chance each year of infection, if the CD4+ T- in pregnant women who have serologic evidence of helper cell count is below 200. Clinically, this illness previous exposure, most likely because of a protec- presents with fever, shortness of breath, a nonproductive immune response. Pregnant women should tive cough, and eventually death if not properly treated. avoid cats!! Chest X-ray may show diffuse bilateral interstitial in- Like rubella (see Chapter 28), congenital toxoplasmo- filtrates, or it can be normal. sis can cause many problems, including chorioretinitis, blindness, seizures, mental retardation, microcephaly, The Case of the Breathless Woman Who Had encephalitis, and other defects. If the infection is ac- No Helpers quired early during gestation, the disease is severe, often resulting in stillbirth. Interestingly, infants that A 22 year-old female comes to the hospital with fever appear normal can develop disease later in life. Clinical and a feeling of chest tightness. She says she has no reactivation results most commonly in retinal inflam- medical problems but has lost weight. On physical ex- mation (chorioretinitis, which can result in blindness) amination you find large lymph nodes everywhere and that flares late in life (peak incidence in second or third numerous genital warts. You note that she is tachy- decade). pneic, breathing 30 breaths per minute. Note that immunocompetent adults (such as the You look over her past record and find that she had a pregnant women described above) who are infected with child that was born with AIDS. Taa gdii often develop generalized lymph Her chest film shows diffuse perihilar interstitial node enlargement. streaking bilaterally, sparing the outer lung margins. You order an absolute T4-cell count and find that she has 150 T-helper cells (Normal is greater than 1000). BIG PICTURE: In AIDS patients and fetuses Diagnosis of Peci caiii can be made by Toxoplasma gondii is TOXIC to the BRAIN and silver-staining alveolar lung secretions, revealing the EYES!!! flying saucer-appearing fungi. These secretions can be Diagnosis of toxoplasmosis can be made by: obtained as follows, in order of increasing yield: 1) CAT scan of brain will show a contrast-enhanc- 1) Induce a sputum sample by spraying saline into ing mass. the bronchioles and collecting the coughed material 2) Examination of the retina of the eye will reveal (60% sensitivity). retinal inflammation. 2) Insert a fiberoptic camera (bronchoscope) deep 3) Serology: Elevated immunoglobulin titers suggest into the patients bronchial tree, inject saline, and then that the patient has at some time been exposed to this wash it out (bronchoalveolar lavage) (98% sensitivity). organism. 3) Biopsy the lung by bronchoscopy (100% sensitivity). Sulfadiazine plus pyrimethamine can be used to About 80% of AIDS patients will get PCP at least treat patients with acute toxoplasmosis. once in their lifetime unless prophylactic trimetho-

239 CHAPTER 30. PROTOZOA

Figure 30-6

prim/sulfamethoxazole is given when CD4+ T-cell di, ia and Padi ae burst loose counts drop below 200-250. More than 60% of PCP in- every 48 hours. The people who discovered all this fections are being prevented with this prophylactic in- started numbering things with one (they didnt have a tervention! Symptomatic patients can be treated with zero) and so zero hours was called one, 24 hours high dose trimethoprim/sulfamethoxazole or intra- called two, and 48 hours called three. So, P. ia venous pentamidine. and P. ae produce chills and fever followed by drenching sweats every 48 hours, which is called MALARIA tertian malaria. P. aaiae bursts loose every 72 Plamodim falcipam, Plamodim ia, hours, causing a regular 3-day cycle of fevers and Plamodim oale, and Plamodim malaiae chills, followed by sweats. This is called quartan malaria. P. facia, the most common and deadly Malaria is a febrile disease caused by 4 different pro- of the Padia, bursts red cells more irregularly, tozoa: Padi facia, Padi ia, Pa- between 3648 hours. Thus the chills and fevers tend di ae, and Padi aaiae. They infect to either fall within this period or be continuous, with about 300-500 million persons worldwide each year, re- less pronounced chills and sweats. sulting in 20-40 million deaths. The anopheles mosquito carries the organisms within its salivary glands and in- Plasmodia Life Cycle jects them into humans while it feeds. The organisms then grow in the liver and spread to the human red blood Fig. 30-7. The life cycle of the Padia is complex, cells, where they reproduce. The red cells fill with proto- since the protozoa divide into many different forms with zoa and burst. The red cells all burst at the same time, re- different names. This is clinically important because leasing the protozoa into the bloodstream and exposing the diagnosis of this disease rests on being able to iden- them to the immune system, which results in fever. tify these forms on a slide of a patients blood. Fig. 30-6. The different species of Padi Imagine yourself in Kenya with a patient who has in- burst the red cells at different time intervals. P- termittent shaking chills, fevers, and soaking sweats.

240 Figure 30-7 CHAPTER 30. PROTOZOA

You pull out your little microscope with a reflecting mir- Two of the species, P. ia and P. ae, produce dor- ror light source, tilt it to catch some of the deep red mant forms in the liver (hypnozoites) which can grow African sun, and focus your attention on the smear of years later, causing relapsing malaria. This is why you red cells in front of you. What are those life cycle stages are asked if you have ever had malaria when you donate and what do they look like? blood (an effort to screen out infected blood). Padia undergo sexual division in the anopheles In the mosquito, the gametocytes are sucked into the mosquito and asexual division in the human liver and stomach where the male and female gametocytes fuse. red cells. Lets start with the human: DNA is mixed and the fused gametocytes become an Thin, motile, spindle-shaped forms of the Padia, oocyst. The oocyst divides into many spindle-shaped called sporozoites, swim out of the mosquitos sucker wiggling sporozoites, which disseminate within the and into the human bloodstream. They wiggle their way mosquito. They may find their way into the mosquito to the liver and burrow into a liver cell. This marks the salivary gland and will be injected into the human for beginning of the pre-erythrocytic cycle in the liver, asexual reproduction. so-named because this cycle occurs before the red blood cells (erythrocytes) are invaded. The sporozoite rounds The Disease Malaria up to form a ball within the liver cell. This ball, now called a trophozoite, undergoes nuclear division, form- Malaria is well known for causing periodic episodes of ing thousands of new nuclei. This big mass is now a cell severe chills and high fevers along with profuse sweat- with thousands of nuclei, called a schizont. A cytoplas- ing at 48-72 hour intervals. These episodes commonly mic membrane then forms around each nucleus, creat- last about 6 hours and are associated with the rupture i ng thousands of small bodies called merozoites. The of red blood cells. new overloaded liver cell bursts open, releasing the You can imagine that all these cycles of red blood cell merozoites into the liver and bloodstream. Some will re- lysis must take their toll! In fact, P. facia, the i nfect other liver cells as the sporozoite did initially, re- most aggressive species, will invade up to 30% of ery- peating the same cycle discussed above, which is now throcytes, which results in anemia and sticky red blood called the exo-erythrocytic cycle. cells. These sticky cells plug up post-capillary venules in Other merozoites will enter the bloodstream and organs such as the kidney, lung, and even brain, result- enter red blood cells, starting the erythrocytic cycle. ing in hemorrhages and blocked blood delivery to those This cycle is similar to the exo-erythrocytic cycle, tissues. Renal failure, lung edema, and coma may en- except that it occurs in the erythrocytes rather than sue, leading to death. Most deaths occur in children less the liver cells. The merozoite rounds up to form a than 5 years old in sub-Saharan Africa. These children trophozoite. In the red cells the trophozoite is shaped often develop cerebral malaria characterized by like a ring with the nuclear material looking like the seizures and impaired consciousness, leading to coma. diamond on the ring. Nuclear division then occurs with Even with treatment, 20% of children with cerebral formation of a large multinucleated schizont. Cyto- malaria will die. plasm surrounds each nucleus to form new merozoites Infected individuals also get hepatomegaly and within the late schizont. Red cell lysis occurs with splenomegaly. The spleen and liver enlarge as the fixed release of merozoites. The released merozoites stimu- phagocytic cells (of the reticuloendothelial system) pick late an immune response, manifested as fevers, chills, up large amounts of debris from the destroyed red blood and sweats. cells. The enlarged spleen occasionally ruptures. The merozoites can continue to invade other red cells Many African-American and African blacks are resis- and then grow for another 2-3 day cycle followed by rup- tant to P. ia and P. facia infection. The resis- ture and release again. Some merozoites will change tance to P. ia is based on the absence of red cell into male and female gametocytes. These cells circu- membrane antigens Duffy a and b that the P. ia late and will be taken up by a biting anopheles mos- uses for binding. The sickle cell anemia trait (hemoglo- quito. If they are not, they will shortly die. bin AS) appears to help protect the red cells from P.

Figure 30-8 MALARIA

242 I CHAPTER 30. PROTOZOA

falciparum invasion. Endemic infection with malaria in the African continent is thought to have led to a Dar- winian selection process, resulting in high levels of sickle trait and absence of Duffy a and b in many African and African-American blacks.

Fig. 30-8. Comparison of the Plasmodia species. Diagnosis Figure 30-9 1) Examination of thin and thick smears (1000x) of blood, under oil-immersion magnification, reveals the acute infection will subside, but relapses will occur. trophozoites and schizonts within the erythrocytes. Treatment with Primaquine will kill the liver holdouts. Sometimes the gametocytes can be visualized. 2) Fluorescently labeled antibodies may be used to Primaquine is the Prime drug to kill identify the responsible species. P. vivax and P. orale in the liver! 2) Plasmodium falciparum: This guy is nasty, caus- Control of Malaria ing the most hemolysis, organ damage, and death. a) Chloroquine-sensitive areas: Huh, I wonder 1) Prevent mosquito bite: which drug to use?? Chloroquine alone is enough a) Eliminate vector with pesticides (pyrethins) at as P. falciparum does not have an exo-erythrocytic dusk in living and sleeping areas. cycle. b) Use insect repellants (containing DEFT) and b) Chloroquine-resistant areas: Treatment options mosquito nets, and wear long-sleeved shirts and include quinine (quinidine, the antiarrhythmic long pants. drug, is more expensive but readily available in the United States and just as effective), artemether 2) Chemical Prophylaxis for travelers: When traveling (see below), pyrimethamine/sulfadoxine, or to an area without chloroquine resistance, chloroquine mefloquine. Severe infection (cerebral malaria) is is used. If in a chloroquine resistant area, mefloquine or treated with IV or IM quinine, quinidine, or doxycycline may be used for prophylaxis. artemether. It is wise to carry a pyrimethamine/sulfadoxine (fan- sidar) "starter pack" to take in case of breakthrough in- Newsflash!!! Artemether is new therapy for se- fection when far away from medical care. This is vere falciparum malaria in children and adults! especially true with doxycycline. Chloroquine-resistant P. falciparum causes severe Fig. 30-9. Chloroquine-resistant P. falciparum ar- malaria in Africa, killing about 500,000 children a year eas. Malaria is a disease of the tropics, cutting a swath (1-2 million world-wide). Quinine is the preferred ther- across the equator. Chloroquine-resistant Plasmodium apy in these areas because it can be injected intramus- falciparum areas include most of Africa, Central Amer- culary (IM). A new drug named artemether (or its ica south of the Panama Canal, South America, India, brother artesunate) is derived from a traditional Chi- and South East Asia (see map). Chloroquine-sensi- nese malaria remedy (qinghaosu or wormwood!). tive areas include North Africa, Central America North Artemether is effective against chloroquine-resistant P. of the Panama Canal, Haiti, and the Middle East. falciparum and has proven to work as well as quinine in the treatment of severe malaria. Unfortunately, even with therapy, 20% of children with cerebral malaria still die. (Hoffman, 1996; Van Hensroek, 1996; Hien, 1996; Treatment of Malaria White, 1996). To treat malaria you must understand two concepts: 1) the geographic pattern of susceptibility of P. falci- There are a number of common features of these parum to antimalarial drugs ( Fig. 30-9.) and 2) the type drugs (also see Fig. 30-13). ofPlasmodium species causing the infection. 1) All of the anti-malarial drugs can be taken orally. 1) P. malariae, P. vivax, and P. ovale are all suscepti- 2) All of the anti-malarial drugs cause GI upset as a ble to chloroquine! Pushovers! But don't forget that P. primary adverse effect. vivax and P. ovale have exo-erythrocytic cycles in the 3) Chloroquine, primaquine, and quinine all cause liver and will be protected there from chloroquine. The hemolysis in patients with glucose-6-phosphate dehy-

243 CHAPTER 30. PROTOZOA

Figure 30-10

drogenase deficiency (G-6-P-D deficiency is present BABESIOSIS in some Africans, Mediterraneans, and Southeast (Babesia microti, Babesia divergens) Asians). 4) Chloroquine, quinine, quinidine, and sulfadoxine/ Babesiosis is an infection very much like malaria. It is pyrimethamine are safe in all trimesters of transmitted by the bite of a blood sucker (tick in this case) pregnancy. Not enough data is available about the and it invades and can be seen inside, red blood cells. It others. also causes fever and hemolysis (anemia), as in malaria.

244 CHAPTER 30. PROTOZOA

It is diffee in that: cause different diseases, they pass through similar morphologic states in the human and insect host. They can ex- 1) There are more than 100 species f Babeia, mostly ist as rounded cells without flagella, called amastigotes, causing disease in cattle and other domestic or wild or as flagellated motile forms called promastigotes, epi- animals. mastigotes, and trypomastigotes. These are named 2) Babeia are spread by tick bites, mosquito bites. according to the insertion site ftheir single flagellum. All 3) They do not affect liver cells (so there is no exoery- fthese organisms cause an initial skin ulcer at the site f throcytic phase). the insect bite, followed by systemic invasion. In the northeastern coastal United States (e.g. Nan- These parasites can also be transmitted via blood tucket Island) Babeia Mici i spread by the bite f product transfusion. the same tick that spreads lyme disease, Ide ca- ai. After biting the white-footed mouse, the reservoir Leishmaniasis for B. ici, the tick will leap to the next carefree (Leihaia ica, Leihaia chagai, Leihaia golfer who walks into the rough. aj, Leihaia baiiei, Leihaia dai) Like Padi, Babeia sporozoites slither out f tick salivary glands into the blood f the hapless golfer. Leihaia i zoonotic, carried by rodents, dogs, and The sporozoites invade erythrocytes and differentiate foxes, and is transmitted to humans by the bite f the into pear or ring-shaped trophozoites. Trophozoites sandfly. The disease leishmaniasis is found in South asexually bud and divide into 4 merozoites that stick to- and Central America, Africa, and the Middle East. gether, forming a cross or x-shaped tetrad ("Maltese Following transmission from the sandfly, the pro- cross"). Red cell infection results in only mild hemolysis, mastigote invades phagocytic cells (macrophages) and so infection is usually asymptomatic and sub-clinical. transforms into the nonmotile amastigote. The amastig- Asplenic patients are unable to clear the organisms as ote multiplies within the phagocytic cells in the lymph well and may have severe infection similar to faci- nodes, spleen, liver, and bone marrow (the reticuloen- a malaria. (Gelfand, 1995; Persing, 1995). Treat dothelial system) (see Fig. 30-10). infected patients with quinine and clindamycin. The different diseases caused by Leihaia depend on the invasiveness f the species as well as the hosts immune response. Host immunity depends on a cell-mediated defense. It appears that some patients have genetically deficient defenses against Leihaia and will be afflicted with more severe disease. Leishmania- sis presents in a spectrum f disease severity: from a single ulcer that will heal without treatment; to widely disseminated ulcerations f the skin and mucous membranes; to the very severe infection striking deep into the reticuloendothelial organs, the spleen and liver. Note the similarity here to leprosy (see Chapter 14) in which differences in host cell-mediated defenses result in varied severity f disease. There are 3 clinical forms f this disease:

1) Cutaneous leishmaniasis a) Simple cutaneous lesions b) Diffuse cutaneous lesions Fig. 30-9A. Babesia sporozoites in the "hood". 2) Mucocutaneous leishmaniasis Giemsa or wright-stained thin and thick blood smears 3) Visceral leishmaniasis reveal ring-shaped trophozoites that look like Pad- i and the distinctive cross or x-shaped tetrad f Cutaneous Leishmaniasis merozoites (Maltese cross). Transmitted by tick vector. A sandfly injects Leihaia into the skin, where they migrate to reticuloendothelial cells (fixed phago- THE BLOOD-BORNE FLAGELLATES cytic cells in lymph nodes). At the site f the sandfly (Leihaia and Taa) bite, a skin ulcer develops, called an "oriental sore." This ulcer heals in about a year, leaving a depigmented (pale) Fig. 30-10. Leihaia and Taa are trans- scar. Diagnosis is made by observing Leihaia i mitted by the bite fa blood-sucking insect. Although they stained skin-scrapings from the ulcer base.

245 CHAPTER 30. PROTOZOA

Cell-mediated immunity is intact, so the immune sys- test is negative during active disease as cell-mediated tem attacks the organisms resulting in skin destruction immunity is deficient. (ulcer formation) and clearance of infection (similar to All forms of leishmaniasis can be treated with the the situation with tuberculoid leprosy). Because of the pentavalent antimonial stibogluconate. intact cell-mediated immunity, this organism invokes a delayed hypersensitivity reaction. Diagnosis can be African Sleeping Sickness made by injecting killed Leishmania intradermally (Leishmania skin test). Just like the PPD test of tuber- (Taa bcei hdeiee and Taa culosis, a raised indurated papule 48 hours later sup- bcei gabiee) ports the presence of a Leishmania infection. Trypanosoma rhodesiense and Trypanosoma gambi- This disease is also seen in Latin America and Texas, ense are responsible for African sleeping sickness, which where it is called American cutaneous leishmaniasis. is transmitted by the blood-sucking bite of a tsetse fly. Following this bite, the motile flagellated form of these Diffuse Cutaneous Leishmaniasis 2 organisms, called a trypomastigote, spreads via the person's bloodstream to the lymph nodes and central In Venezuela and Ethiopia, a chronic form of cuta- nervous system (CNS) (see Fig. 30-10). neous leishmaniasis occurs in patients with deficient The first manifestation is a hard, red, painful skin ul- immune systems. A nodular skin lesion arises but does cer that heals within 2 weeks. With systemic spread, the not ulcerate. With time, numerous nodular lesions arise patient then experiences fever, headache, dizziness, and diffusely across the body. There is often a concentration lymph node swelling. These symptoms can last a week, of lesions near the nose. The untreated infection can last and then the fever subsides for a few weeks followed by more than 20 years. renewed fevers. This pattern of fevers with fever-free in- The disease is diffuse because the host's immune tervals can occur for months. Finally, CNS symptoms system does not respond to the invasion by Leishma- develop, with drowsiness in the daytime (thus sleeping nia, due to a defect in cell-mediated immunity. There- fore, the promastigotes are able to spread and infect sickness), behavioral changes, difficulty with walking, slurred speech, and finally coma and death. the skin, causing the diffuse nodular lesions. Due to There are 2 forms of African sleeping sickness. West the defect in cell-mediated immunity, the Leishmania African sleeping sickness, caused by Trypanosoma skin test is negative (similar to the situation in lepro- brucei gambiense, is notable for slowly progressing matous leprosy). fevers, wasting, and late neurologic symptoms. East African sleeping sickness, caused by Trypanosoma Mucocutaneous Leishmaniasis brucei rhodesiense, is similar to the West African vari- Initially, a dermal ulcer, similar to cutaneous leishma- ety but more severe, with death occurring within weeks niasis, arises at the site of the sandfly bite and soon heals. to months. There is rapid progression from recurrent However, months to years later, ulcers in the mucous fevers to early neurologic disease (drowsiness, mental membranes of the nose and mouth arise. If untreated, the deterioration, coma, and death). infection is chronic, with erosion of the nasal septum, soft palate, and lips, over a course of 20-40 years. Death by Q: Why the intermittent fevers??? bacterial secondary infection may occur. A: Variable surface glycoproteins (VSG). The Diagnosis is made via skin scrapings. trypanosomes are covered with about 10 million molecules of a repeating single glycoprotein called the VSG. Visceral Leishmaniasis (Kala-azar) The trypanosomes possess genes that can make thousands of different VSGs. They will make and express, on The sandfly transmits Leishmania donovani or Leish- their surface, a new VSG in a cyclical nature. Every mania chagasi to an individual (most commonly young malnourished children), who months later will complain time the human host develops antibodies directed of abdominal discomfort and distension, low-grade against the VSG (and fever with this immune recogni- fevers, anorexia, and weight loss. This abdominal en- tion), the trypanosomes produce progeny with a new VSG coat. Thus, there are waves of new antigens, pro- largement is due to Leishmania donovani's invasion of the reticuloendothelial cells (fixed phagocytic cells) of the ducing recurrent fevers and protection from our im- spleen and liver, causing hepatomegaly and massive mune defenses. This is similar to the antigenic variation splenomegaly. Patients also develop a severe anemia of the spirochete Borrelia recurrentis, which causes re- and the white blood-cell count can also be very low. Most lapsing fever (see Fig. 13-12). cases (over 90%) are fatal if untreated. Diagnosis is made by liver and spleen biopsies Diagnosis consists of visualization of trypomastigotes demonstrating these protozoa. The Leishmania skin in peripheral blood, lymph nodes, or spinal fluid.

246 CHAPTER 30. PROTOZOA

Figure 30-11

Patients are treated with suramin if the central ner- Cates while it eats. T. ci trypo-mastigotes, which are vous system (CNS) is not involved (suramin does not present in the bugs feces, tunnel into the human host. penetrate into the CNS). With CNS involvement, the ar- The trypomastigote loses its undulating membrane and senical melarsoprol, which is extremely toxic, is used. flagellum and rounds up to form the amastigote, which rapidly multiplies. Organisms invade the local skin, Chagas' Disease macrophages, lymph nodes, and spread in the blood to distant organs (see Fig. 30-10). (Taa ci , the American Trypanosome) Chagas disease is caused by a trypanosome, but the Acute Chagas Disease pathogenesis and epidemiology differ greatly from the African trypanosomes. At the skin site of parasite entry, a hardened, red This is truly a disease of the Americas, ranging from the area develops, called a chagoma. This is followed by southern U. S. (Texas), Mexico, Central America, and systemic spread with fever, malaise, and swollen down into South America. T. ci survives in wild animal lymph nodes. Organs that can be infected include the reservoirs such as rodents, opossums, and armadillos. heart and central nervous system (CNS). Heart in- The vector is the reduviid bug, also called the kissing flammation results in tachycardia and electrocardio- bug. The bug feeds on humans while they sleep and defe- graphic changes, while the CNS involvement can

247 CHAPTER 30. PROTOZOA result in a severe meningoencephalitis (usually in individuals should take precautions to prevent kisses by young patients). the kissing bug (insect repellent, bednets). This acute illness resolves in about a month and patients then enter the intermediate phase. In this Balantidium Coli phase there are no symptoms, but there are persistently If you do not want diarrhea, do not consume food or low levels of parasite in the blood as well as antibodies water contaminated by pig feces! This advice will pre- against T. ci. Most persons will remain in the inter- vent ingestion of B. ci cysts. These cysts mature into mediate phase for life. ciliated trophozoites, and travel to the intestinal tract. For reasons that are poorly understood, some per- The trophozoites dig into the intestinal wall, where they sons will develop chronic Chagas disease years to exist happily consuming the native bacteria. Most in- decades later. fected individuals are asymptomatic, while some will develop diarrhea. Chronic Chagas Disease B. Ci trophozoites are notable for being the largest parasitic protozoans found in the intestine. Diagnosis is The organs primarily affected are the heart and some made by identifying the ciliated trophozoites or cysts in hollow organs such as the colon and esophagus. Intra- stool specimens. Tetracycline is effective at treating this cellular T. ci amastigotes cannot usually be found, infection. and it is unclear why disease develops in these organs. Fig. 30-12. Summary of the protozoan diseases. 1) Heart: Arrhythmias are the earliest manifesta- Fig. 30-13. Treatment of protozoan diseases. tion (heart block and ventricular tachycardia). Later there is an increase in heart size and heart failure (dilated cardiomyopathy). References 2) Megadisease of colon and esophagus: A big, Dupont HL, Chappell CL, et al. The infectivity of C- dilated, poorly functioning esophagus develops with idi a in healthy volunteers. N Engl J Med symptoms of difficulty and pain in swallowing, and re- 1995;332:855-9. gurgitation of food. A dilated colon (megacolon) results Gelfand JA. Babesia. In: Mandell GL, Bennett JE, Dolin R, in constipation and abdominal pain. Patients can go eds. Principles and Practice of Infectious Disease. 4th ed. weeks without bowel movements. New York: Churchill Livingstone, 1995:2415-2427. Hein TT, Day NP, et al. A controlled trial of artemether or quinine in Vietnamese adults with severe falciparum malaria. Fig. 30-11. Taa ci (the American Try- N Engl J Med 1996;335:76-83. panosome). To remember that T. ci causes mega- Hoffman SL. Artemether in severe malaria-still too many colon, electrical arrhythmias ,and dilatation of the deaths. N Engl J Med 1996;335:124-5. heart, and is transmitted by the feces of the kissing bug, Kirchhoff LV. American trypanosomiasis (Chagas disease) -a picture Tom Cruise (the American actor). tropical disease now in the United States. N Engl J Med 1993;329:639-644. Krogstad DJ. Plasmodium species (malaria). In: Mandell GL, Diagnosis and Treatment Bennett JE, Dolin R, eds. Principles and Practice of Infec- tious Disease. 4th ed. New York: Churchill Livingstone, Acute Chagas disease: 1995:2415-2427. Persing DH, Herwaldt BL, et al. Infection with a Babesia-like 1) Direct examination of the blood for the motile try- organism in northern California. N Engl J Med 1995; pomastigotes. 332:298-303. 2) Xenodiagnosis: This sensitive test is conducted Rosenblatt JE. Antiparasitic Agents. Symposium on Antimi- as follows. Forty laboratory-grown reduviid bugs are al- crobial Agents-Part VII. Mayo Clin Proc 67:276-287, 1992. lowed to feed on the patient, and one month later the Sanford JP, Gilbert DN, et al. Guide to Antimicrobial Therapy bugs intestinal contents are examined for the parasite. 1996. Antimicrobial Therapy, Inc, Dallas Texas; 1996. Ungar BL. Cryptosporidium. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Disease. Chronic Chagas disease: 4th ed. New York: Churchill Livingstone, 1995:2500-2510. Van Hensbroek MB, Onyiorah E, et al. A trial of artemether Classic clinical findings (cardiac and megadisease) or quinine in children with cerebral malaria. N Engl J Med along with serologic evidence of past T. ci infection 1996;335:69-75. allows for presumptive diagnosis. White NJ. Current concepts: The treatment of malaria. N Although nifurtimox and benznidazole can be used Engl J Med 1996;335:800-06. for acute cases, there is currently no effective therapy for Wyler DJ. Malaria chemoprophylaxis for the traveler. N Engl the chronic manifestations of this infection. Therefore, J Med 1993;329:31-37.

248 Clinical Microbiology Made Ridiculously Simple ®MedMaster Figure 30-12 PROTOZOA M. Gladwin and B. Trattler, Figure 30-13 ANTI-PARASITIC DRUGS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple OMedMaster CHAPTER 31. HELMINTHS CHAPTER 31. HELMINTHS

Helminths is Greek for "worm." Worms are usually testinal wall and travel in the bloodstream to the lungs. macroscopic, although diagnosis often requires the vi- The larvae grow in lung alveoli until they are coughed sualization of the eggs, which are microscopic, in the up and swallowed. These larvae again reach the small stool. We will discuss 16 types of worms that cause sig- intestine and mature into adults. Here each adult worm nificant infections in humans. The first 10 are round- produces over 200 thousand eggs per day, which are ex- worms (nematodes), and the last 6 are the more creted in feces. primitive flatworms (platyhelminthes). By under- 2) Necator americanus: The larval form lives standing their life cycles, you can learn ways to prevent in the soil and eats bacteria and vegetation. After or eradicate helminthic infections. a week it transforms into a long, slender filari- Within the normal human host there is usually form larva that can penetrate human skin. The no immune reaction to living worms. However, there filariform larva penetrates between the toes of the is often a marked response to dead worms or eggs. With hapless human who walks by shoeless. The larvae travel many of the worm infections, our immune system is directly to the alveoli of the lungs, where they grow and kind enough to raise a red flag-elevating the level of are coughed up and swallowed. The adult worms de- eosinophils in the blood-thereby assisting in diagnosis. velop as they arrive at the small intestine, where they attach by their mouths, and suck blood. At this point, the hookworms copulate and release fertilized eggs. NEMATODES 3) Strongyloides stercoralis: The larval forms in (Roundworms) the soil penetrate the human skin and travel to the lung. There they grow, are coughed up and swallowed into the Intestinal Nematodes small intestine, where they develop into adult worms that lay eggs. The eggs are not passed in the stools. "Intestinal" nematodes all mature into adults within Rather, filariform larvae hatch and can do 3 things: the human intestinal tract. The larval forms of many of a) Autoinfection: The filariform larvae pene- these roundworms may be distributed widely through- trate the intestine directly, without leaving, and go out the body. to the lung to continue the cycle. Three of the intestinal nematodes are acquired by the b) Direct cycle: The filariform larvae pass out in ingestion of eggs: Ascaris lumbricoides, Trichuris the feces, survive in the soil, penetrate the next trichiura ( whipworm), and Enterobius vermicularis passerby, and migrate to the lungs. This complete (pinworm). Two worms, Necator americanus ( hook- cycle is almost exactly the same as that of Necator worm) and Strongyloides stercoralis, are acquired when americanus ( hookworm). their larvae penetrate though the skin, usually of the c) Indirect cycle: This is a sexual cycle where foot. Trichinella spiralis is acquired by the ingestion of the filariform larvae are passed out in the stool and encysted larvae in muscle (pork meat). while in the soil develop into male and female With infection, most of these intestinal worms (except adults. They mate in the soil and produce fertilized for Enterobius and Trichuris, which stay in the intesti- eggs. The filariform larvae then hatch and reinfect a nal tract) invade other tissues at some stage of their life human, moving to the lung. cycle. This stimulates our immune system to raise the number of eosinophils in the blood. Ascaris lumbricoides Fig. 31-1. Ascaris infection may be mild or asympto- Fig. 31-1. The first 3 roundworms (Ascaris lumbri- matic. With heavy infections the patient may develop ab- coides, Necator americanus, and Strongyloides sterco- dominal cramping. Severe infections involve adult worm rous) all have a larval form that migrates through invasion into the bile ducts, gall bladder, appendix, and the tissue and into the lung at some stage of their life liver. Children with heavy worm loads may suffer from cycle. The larvae grow in the lung, are coughed up and malnutrition because the worms compete for the same food swallowed into the intestine, where they grow into and sometimes a mass of worms can actually block the in- adult worms. testine. When the larvae migrate into the lung, the patient may develop cough, pulmonary infiltrate on chest 1) Ascaris lumbricoides: Infection occurs in the x-ray, and a high eosinophil count in the blood and sputum. tropics and mountainous areas of the southern U. S., Diagnosis is made by identification of eggs in feces. A when individuals consume food that is contaminated sputum examination may reveal larvae. The peripheral with eggs. Larvae emerge when the eggs reach the blood smear may also reveal an increased number of small intestine. The larvae penetrate through the in- eosinophils.

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Figure 31-1

Treatment ralis, Enterobius vermicularis (pinworm), Trichuris trichiura (whipworm), and Trichinella spiralis are all The intestinal nematodes Ascaris lumbricoides, treated with the same drug: Necator Americanus (hookworm), Strongloides sterco-

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Think of a worm, may also demonstrate larvae. Examination of the blood Worms BEND, will reveal an elevated level of eosinophils. BEND them a lot and you can kill them! Treat infected patients with thiabendazole or albendazole and ivermectin Mebendazole Thiabendazole Trichinella spiralis Albendazole You may have seen Gary Larsons "The Far Side" comic These drugs paralyze the roundworms so they are showing wolves at the edge of a pork farm, saying, "Lets passed out in the stool. Other drugs will irritate the rush them and Trichinella be damned." After reading worms, causing them to migrate out of the small intes- about Trichinella spiralis, we can finally get the joke. tine to other organs, which can be fatal. Infection occurs following the ingestion of the encysted Pyrantel pamoate is an alternative agent for En- larvae of Trichinella spiralis, which are often present in terobius (pinworm), Necator (hookworm), and Ascaris. raw pork. After ingestion, the cysts travel to the small intestine, where the larvae leave the cysts and mature into mating adults. Following mating, the adult males are Necator americanus and Ancyclostoma passed in the feces. The females penetrate into the in- duodenale testinal mucosa, producing thousands of larvae. The lar- (Hookworm) vae then enter the bloodstream and spread to organs and skeletal muscle. The larvae then become encysted in Fig. 31-1. Notice that Ascaris lumbricoides and Neca- skeletal muscle, where they may last for decades. tor americanus (hookworm) have very similar life cy- Most patients are asymptomatic with the initial cles. They differ only in the path that each larvae form infection. Some patients will complain of abdominal takes to reach the lung: Necator, foot to lung; Ascaris, pain, diarrhea, and fever as the worms mature in the intestine to lung. small intestine and penetrate through the intestinal The patient with hookworm can develop diarrhea, ab- wall. About 1 week after the initial intestinal invasion, dominal pain, and weight loss. Since each hookworm the larvae migrate into skeletal muscle, producing sucks blood from the wall of the intestine, hookworm in- fevers and muscular aches. In severe (sometimes fatal) fection may cause an iron deficiency anemia. There is cases, larvae may invade heart muscle and brain tissue. also an intense itching and rash at the site of penetra- Diagnosis can be made with serologic tests or muscle tion through the skin (between the toes), and the local biopsy, which will reveal the encysted larvae. Since there growth in the lung can result in a cough, infiltrate on is significant muscle invasion, examination of the differ- chest x-ray, and eosinophilia. ential white blood cell count will reveal a marked increase Diagnosis is made by identifying eggs in a fresh fecal in the percentage of eosinophils. The invasion of muscle sample. This infection may be treated with mebenda- also results in increased levels of serum muscle enzymes, zole. Also treat the iron deficiency anemia. such as creatinine phosphokinase (CPK). Prevention is best carried out by killing cysts, either by Strongyloides stercoralis cooking or freezing the pork meat prior to consumption. Mebendazole and thiabendazole have little effect Fig. 31-1. Individuals infected with Strongloides on muscle larvae but may be helpful. may complain of vomiting, abdominal bloating, diarrhea, anemia, and weight loss. Similar to hookworm infection, patients may develop a prurititic rash, lung symptoms Trichuris trichiura (cough or wheezing), and/or eosinophilia. When patients (Whipworm) infected with strongyloides are given immunosuppressive medications, such as prednisone, they can develop The next 2 worms, Trichuris trichiura and Enterobius a severe autoinfection. The filariform larvae will invade vermicularis, have very simple life cycles: there is no fi- the intestine, lung and other organs, causing pneumonia, lariform larvae stage, no tissue invasion, and no lung in- ARDS, and multi-organ failure. Patients with COPD volvement. Since there is no tissue invasion, the and asthma living in areas endemic for Strongyloides eosinophil count is not elevated. should have their stool and eosinophil count checked before steroid treatment! Fig. 31-2. Trichuris trichiura has a simple slow Diagnosis is made by identifying larvae in feces (no life cycle. Like the Congressional whip trying to move eggs). The enterotest, where a long nylon string is his party to a decision, the whipworm life cycle is swallowed and later pulled back out the mouth, may slow. Transmission occurs by ingestion of food conta- demonstrate larvae of Strongloides. Sputum exam minated with infective eggs. The eggs hatch in the

253 CHAPTER 31. HELMINTHS

Figure 31-2

gastrointestinal tract and migrate to the cecum and can be viewed under a microscope. At night the larger ascending large intestine. The mature adult will then adult females can sometimes be seen with the unaided produce thousands of eggs per day for about one year. eye, crawling across the perineal area. There is no There is no autoinfection, since the eggs must incu- eosinophilia, since there is no tissue invasion. bate in moist soil for 3-6 weeks before they become Treat with mebendazole or pyrantel pamoate, infective. avoid scratching, and change the sheets daily. Infected patients may have abdominal pain and diarrhea. Diagnosis is made by identifying eggs in fecal Fig. 31-3. Enterobius vermicularis. The female worm is specimens. The eggs look like footballs with bumps on like an intestinal (entero) bus. She drives out of the each end. The adults have the appearance of a bullwhip, anus every night and drops off her egg passengers on thus the common name. the perineum. If a pin (pinworm) pops her tire, seal Treat patients with mebendazole. the leak with some scotch tape. The scotch tape test is used to diagnose Enterobius vermicularis i nfection. Enterobius vermicularis (Pinworm) Blood and Tissue Nematodes The Enterobius' life cycle is very simple: The eggs are The blood and tissue nematodes are not spread by fe- simply ingested, and the pinworms mature in the cecum cal contamination, but rather by the bite of an arthro- and ascending large intestine. The female migrates to pod. These threadlike, round worms belong to the the perianal area (usually at night) to lay her eggs, family Filarioidea and so are called filariae. Adult fi- which become infectious 4-6 hours later. This infection lariae live in the lymphatic tissue and give birth to causes severe perianal itching. An infected individual prelarval forms (they do not lay eggs) called microfi- will scratch the perianal area and then reinfect himself lariae. The microfilariae burrow through tissue and or others (hand-to-mouth) because his hands are now circulate in the blood and lymphatic system. Microfilar- covered with the microscopic pinworm eggs. iae are picked up by bloodsucking arthropods, which This infection is more of a nuisance than it is danger- transmit them to another human. Disease is caused ous. The infected individual has a terribly itchy behind, by allergic reactions to both the microfilariae and usually at night. dead adult worms in the lymphatic system as well as Diagnosis is made by placing scotch tape firmly on the other organs (such as the eyes with Onchocerca volvu- perianal area. The scotch tape will pick up eggs, which lus infection).

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Figure 31-3

Onchocerca volvulus mans are the only reservoir, treating people in endemic areas for 10 years (as planned) will prevent the birth of This filarial infection is found in Africa and Central new microfilariae while all the adult worms (which have and South America. The larvae are transmitted to hu- long life spans) die of old age. mans by the bite of infected black flies. The microfi- If you know Spanish, ver means "to see." So: I VER lariae (larvae) mature into adults, which can be found with IVERmectin!! coiled up in fibrous nodules in the skin and subcutaneous tissue. After mating, the adults produce micro- Wuchereria bancrofti and Brugia malai filariae, which migrate through the dermis and connec- ( Elephantiasis) tive tissue. Patients will develop a pruritic skin rash with darkened pigmentation. The skin may thicken Wuchereria bancrofti and Brugia malai both cause a with the formation of papular lesions that are actually lymphatic infection that can result in chronic leg intraepithelial granulomas. The thickened skin may swelling. Wuchereria infection is endemic to the Pacific appear dry, scaly, and thick ("lizard skin"). Microfilar- Islands and much of Africa, while Brugia is endemic to iae may also migrate to the eye, causing blindness the Malay Peninsula and is also seen in much of South- (since the black fly vector breeds in rivers and streams, east Asia. Transmission occurs by the bite of an infected this is often referred to as "river blindness"). There mosquito. The transmitted microfilariae mature into are villages in endemic areas where most of the inhabi- adults within the lymphatic vessels and lymph nodes of tants are blind. the genitals and lower extremities. Mature adults mate, Diagnosis is made by demonstrating microfilariae in and their offspring (microfilariae) enter nearby blood superficial skin biopsies, or adult worms in a nodule. vessels. Microfilariae can often be seen in the eye (cornea and Small infections may only result in enlarged lymph anterior chamber) by slit lamp examination. nodes. Frequent infections in endemic areas result in A new drug, ivermectin, has revolutionized the acute febrile episodes, associated with headaches and treatment of Onchocerciasis. It kills microfilariae and swollen inguinal lymph nodes. Occasionally, following prevents the microfilariae from leaving the uteri of repeated exposures, fibrous tissue will form around adult worms. The manufacturer (Merck) has donated dead filariae that remain within lymph nodes. The fi- the drug to the World Health Organization for a pro- brous tissue plugs up the lymphatic system, which re- gram to eradicate Onchocerca from the planet. As hu- sults in swelling of the legs and genitals. The swollen

255 CHAPTER 31. HELMINTHS

rience allergic symptoms, including nausea, vomiting, hives and breathlessness, during the larval release. A common practice used to remove the worm involves driving a small stick under the part of the worms body that is looped out of the skin. The stick is slowly twisted each day to pull out the 100 cm Dracunculus.

Cutaneous Larval Migrans Also called creeping eruption, this intensely pruritic, migratory skin infection commonly occurs in the Southeastern U.S. The larvae of dog and cat hookworms penetrate the skin and migrate beneath the epidermis. As these larvae move (a few centimeters per day), an al- Figure 31-4 lergic response is mounted, resulting in a raised, red, itchy rash that moves with the advancing larvae. The dog hookworm Ancyclostoma braziliense and (edematous) areas become covered with thick, scaly other species are responsible. skin. This chronic disfiguring manifestation is called Human tissue-invasive nematodes such as the hook- elephantiasis because the extremities take on the ap- worm (Necator americanus) and Strongyloides sterco- pearance of elephant legs. ralis can produce similar creeping eruptions. Diagnosis is made by the identification of microfilar- Diagnosis is made by biopsy of the advancing edge of iae in blood drawn at nighttime. (For poorly understood the rash. reasons, very few organisms circulate during daylight hours. This is called Nocturnal periodicity.) Diagno- PLATYHELMINTHES sis can also be made by identification of positive antibody titers via immunofluorescence. (Flatworms) Diethylcarbamazine is the agent used to treat ele- Flatworms do not have a digestive tract. There are phantiasis. Lymphatic damage may require surgical 2 groups: correction. 1) Trematodes, also known as flukes, include the Fig. 31-4. There are two ( Di) women named Ethyl in freshwater-dwelling schistosomes. Both male and fe- this car: Di-ethyl-car. You will notice that there is an male members exist and mate within humans (not in elephant between Ethyl and Ethyl. You see, the drug the digestive tract, however). All flukes have a water Diethylcarbamazine is used to treat the filarial infec- snail species as an intermediate host. tions caused by Wuchereria bancrofti, Brugia malayi, 2) Cestodes, also known as tapeworms, live and Loa boa, and Onchocerca volvulus. These filariae chron- mate within the human digestive tract. Each tapeworm ically infect the lymphatics, causing lymph obstruction, has both male and female sex organs (hermaphrodites), giant swollen testicles, and elephant legs ("elephantia- so individual tape worms can produce offspring by sis"). Thus the elephant between the Ethyls. themselves.

Dracunculus medinensis Trematodes (Guinea worm) (Flukes) This very interesting tissue-invasive nematode lives as a larval form inside intermediate hosts: African and Schistosoma Asian freshwater copepods (tiny crustaceans). When a (Blood Flukes) person drinks water containing the microscopic crus- Schistosomal infections are extremely common taceans, the larvae penetrate the intestine and move worldwide, second only to malaria as a cause of sickness deep into subcutaneous tissue, where the adults develop in the tropics. Schistosomes are found in freshwater. and then mate. The male is thought to die, but the female They penetrate through exposed skin and invade the ve- grows over the course of a year to a size of 100 cm!!! She nous system, where they mate and lay eggs. Since the then migrates to the skin and a loop of her body pokes out eggs must reach freshwater to hatch, schistosomes can- and exposes her uterus. When the uterus comes into con- not multiply in humans. tact with water, thousands of motile larvae are released. Persons infected with Dracunculus medinensis will expe- Fig. 31-5. The 3 major Schistosoma species worldwide.

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Species Geographic distribution Resides in veins Deposits eggs surrounding in: Schistosoma japonicum Eastern Asia I ntestinal tract Feces Schistosoma mansoni South America and Africa Intestinal tract Feces Schistosoma Africa Bladder Urine haematobium Figure 31-5 SCHISTOSOMES

The Schistosoma life cycle begins when their eggs urine. Instead, these eggs are whisked off by the blood- hatch in freshwater. Larvae emerge and swim until stream, where they are deposited in the liver, lung, or they find a freshwater snail. After maturing within brain. The immune system reacts against these eggs, these snails, the larvae are released and are now infec- walling them off as granulomas. The deposition of eggs tious to humans. Mature schistosomal larvae (called in the venous walls of the liver leads to fibrosis, which cercariae, which look like little tadpoles with oral causes blockage of the portal venous system and a suckers on one end and a tail on the other), penetrate backup of venous pressure into the spleen and mesen- through exposed human skin, and travel to the intra- teric veins (portal hypertension). Any blood vessels or hepatic portion of the portal venous system. At this lo- organs that these eggs get stuck in can become in- cation, the schistosomes rna`ture and mate. Depending flamed, with formation of granulomas and ulcers. Pa- on the species, the pair of schistosomes will migrate to tients may develop hematuria, chronic abdominal pain the veins surrounding either the intestine or the blad- and diarrhea, brain or spinal cord injury, or pulmonary der, where they lay their eggs. These eggs may enter the artery hypertension. lumen of the intestine or bladder, where they may be ex- Diagnosis is based on the demonstration of eggs in creted via feces or urine into a nearby stream or lake so stool or urine samples and high eosinophil counts in the that they can continue their life cycle. blood. Control is directed at the proper disposal of hu- Interestingly, the adult worms in the venous system man fecal waste and elimination of the snails that act are able to survive and release eggs for years, since they as the intermediate host. are not killed by the immune system. It is thought that schistosomes practice molecular mimicry (incorpora- Treatment tion of host antigens onto their surface, which fools the hosts immune system into thinking that the schisto- A group of quantum physicists got together to eradi- somes are NOT foreign). cate this horrible disease. They wanted a drug that kills However, cercariae (mature larvae) and eggs briskly all the flukes and tapeworms also. They succeeded so stimulate the immune system, and are responsible for Praise the quantum physicists! ( Note: This is a lie). the systemic illness caused by this infection. Praziquantel: This is truly a broad spectrum anti- helminthic agent covering cestodes and trematodes Clinical Manifestations alike. When treating patients with praziquantel, dont be surprised if there is an immediate exacerbation of Schistosomiasis has 3 major disease syndromes that symptoms. The death of these schistosomes evokes a occur sequentially: 1) Dermatitis as the cercariae pene- vigorous immune response. trate a swimmers skin, 2) Katayama fever as the grown adults begin to lay eggs, and 3) Chronic fibrosis of organs and blood vessels from chronic inflammation Cestodes around deposited eggs. (Tapeworms) Upon penetration through the skin, patients tran- siently develop intensely itchy skin (swimmers itch) Tapeworms are flatworms that live in the intestine of and rash. Katayama fever follows 4-8 weeks later their host. Since they lack a true digestive tract, they with symptoms that can include fever, hives, headache, suck up nutrients that have already been digested by weight loss, and cough. These symptoms may persist for their host. Tapeworms are hermaphrodites (both male 3 weeks. Lymph node, liver, and spleen enlargement and female organs in the same tapeworm), which en- with eosinophilia are common. ables a single tapeworm to produce offspring. Humans When the schistosomes set up their home in the veins are usually the host of the adult tapeworm while other surrounding the intestines or bladder, they begin re- animals may serve as intermediate hosts for the larval leasing eggs, many of which do not reach the feces or stages.

25 7 CHAPTER 31. HELMINTHS

Figure 31-6

Fig. 31-6. The tapeworm is long and flat (like a Fig. 31-7. Niclosamide is an alternative agent to typewriter ribbon) and consists of a chain of boxlike seg- praziquantel for treatment of tapeworm (cestode) infec- ments called proglottids. Let us examine the tape- tions. Picture a tapeworm wrapped around a nickel or worm from its head down: a nickel under tape. Albendazole and praziquantel are used for the treat- 1) Scolex: The most anterior segment of the tape- ment of Taenia solium larval cysticerci (see below). worm (the head), which has suckers and some-times hooks. 2) Immature proglottids. Taenia solium 3) Mature proglottids have both male and female sex ( Pork Tapeworm) organs. 4) Gravid proglottids contain fertilized eggs. Humans acquire this infection by ingestion of undercooked pork infected with larvae. The pork tapeworm All of the tapeworm infections can be treated with attaches to the mucosa of the intestine via hooks on its praziquantel or niclosamide. scolex and grows to a length of 2-8 meters. It releases

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Cysticerci in the brain tend to cause more symptoms, and this condition is called Neurocysticercosis. There are usually 7-10 cysts in the brain, causing seizures, obstructive hydrocephalus, or focal neurologic deficits. The cysts grow slowly and after 5-10 years begin to die and leak their fluid contents. The antigenic contents cause local inflammation and enhanced symptoms (more seizures, meningitis, hydrocephalus, and focal deficits). In endemic areas such as Mexico, Central and South America, the Philippines, and SE Asia, Cysticercosis is the most common cause of seizures. The diagnosis of cysticercosis is made with the help of a CAT scan or biopsy of infected tissue (brain or muscle), both of which may reveal calcified cysticerci. Newer serologic tests are also proving helpful in the diagnosis of cysticercosis. Symptomatic disease, especially neurocysticercosis, can be treated medically with dibendazole or praziquantel. Note that our immune system raises a red flag to mark this invasion: the elevation of the eosinophil level in the blood.

Taenia saginata ( Beef Tapeworm) Taenia saginata has the exact same life cycle as does Taenia solium, except that humans do not develop cysticerci when they ingest eggs, as do the intermediate hosts (cattle). For this reason, beef tapeworm infection is relatively benign. The beef tapeworm is acquired by the ingestion of larval cysticerci in undercooked beef muscle. The adult Figure 31-7 beef tapeworm develops and adheres (via suckers on its scolex) to the intestinal mucosa, where it may reach a length of over 10 meters and contain more than 2 thou- eggs in the human feces. When pigs graze on fields con- sand proglottids. taminated with the egg-infested human feces, they become the intermediate host. The eggs develop into Patients are usually asymptomatic, although they larvae that disseminate through the intestine and into may develop malnutrition and weight loss. Diagnosis muscle. In the animals muscle tissue, the larvae de- is made by identifying gravid proglottids and/or eggs velop into another larval form, the cysticercus. The in feces. cysticercus is a round, fluid-filled bladder with the larval form within. When a human eats insufficiently Diphyllobothrium latum cooked pork muscle, the larval cysticercus converts to (Fish Tapeworm) the adult tapeworm in the intestine, and the cycle continues (see Fig. 31-8). The fish tapeworm can grow to 45 meters in length. Infected individuals usually have minimal symp- It is acquired by ingesting larvae in raw freshwater toms. Diagnosis is made by demonstration of proglottids fish. The life cycle involves the human and 2 fresh- and/or eggs in a fecal sample. water intermediate hosts, a crustacean and a fish. The Cysticercosis occurs when humans play the role of adult tapeworms in the human intestine drop off their the pig and ingest eggs rather than encysted lar- gravid proglottids loaded with eggs. When the eggs vae. These eggs hatch within the small intestine, and end up in water, they convert to a motile larval form, the larvae migrate throughout the body, where they which is then ingested by a crustacean, which is then penetrate into tissue and encyst, forming cysticerci in i ngested by a freshwater fish (trout, salmon, pike, etc.), the human. Most commonly, the larvae encyst in the which is then ingested by a human-to end this long brain and skeletal muscles (see Fig. 31-8). sentence!

259 CHAPTER 31. HELMINTHS

CYSTICERCOSIS: HUMAN INGESTS EGGS. HATCHED LARVAE PENETRATE HUMAN MUSCLE, BRAIN, LIVER, HEART, AND FORM CYSTICERCI GRAVID PROGLOTTIDS PIGS INGEST AND EGGS EGGS PASS IN FECES 1 CYSTICERCI LARVAE DEVELOP LARVAE DEVELOP INTO ADULT HUMAN PIG AND MIGRATE INTO TAPEWORMS IN PIG MUSCLE HUMAN INTESTINE

HUMAN EATS CYSTICERCI PORK WITH u DEVELOP IN CYSTICERCI PIG MUSCLE

Figure 31-8. Pork tapeworm life cycle.

The large intestinal Diphyllobothrium latum tape- end in the cycle. Echinococcus shares many similarities worm provokes few abdominal symptoms, although it can with Taenia solium, with humans ingesting the eggs. absorb vitamin B12 to a significant degree. If vitamin B,2 These eggs hatch in the intestine and develop into lar- deficiency develops, anemia will occur. Diagnosis of in- vae. After penetrating through the intestinal wall, the fection is made by identification of eggs in the feces. larvae disseminate throughout the body. Most larvae are concentrated in the liver, but larvae may also infect Hymenolepis nana the lungs, kidney and brain. (Dwarf Tapeworm) Each larva forms a single, round fluid-filled "hydatid" cyst. These hydatid cysts can undergo asexual budding This is the smallest tapeworm that infects humans to form daughter cysts and protoscolices inside the orig- (only 15-50 mm in length), and it has the simplest life cy- inal cyst. They can grow to 5-10 cm in size. Each cyst cle. There are NO intermediate hosts. Humans ingest may cause symptoms because it compresses the organ eggs that grow into adult tapeworms, and the adult tape- around it (in the liver, lung, or brain). Humans are ex- worms pass more eggs that are again ingested by humans. tremely allergic to the fluid within the cyst, and if the An infected patient will complain of abdominal cyst bursts, the allergic reaction may be fatal. While the discomfort and occasionally nausea and vomiting. cysts of Echinococcus granulosus simply grow larger, Diagnosis is made by demonstration of eggs in a fecal only to spread if they rupture, E. multilocularis cysts sample. undergo lateral budding and spread. These spreading cysts can be misdiagnosed as a slowly growing tumor. Echinococcus granulosus and Diagnosis of the hydatid cyst employs similar tech- multilocularis niques as with Taenia soliums cysticerci cysts, using (Hydatid Disease, an Extra-intestinal Tapeworm CAT scanning and tissue biopsy. Only 10% of hydatid Infection) cysts cause symptoms, and treatment of these is difficult. The best thing to do is to cut them out of the liver, Fig. 31-9. Dogs and sheep perpetuate the life cycle of lung, or (yikes!) brain, but if the cyst fluid spills, out Echinococcusgranulosus and the human is only a dead- will pour daughter cysts, protoscolices, and highly

260

CHAPTER 31. HELMINTHS

_ HUMANS INGEST LARVAE MIGRATE EGGS INTO TISSUE

EGGS IN DOG SHEEP INGEST STOOL EGGS

LARVAE MIGRATE INTO TISSUE USUALLY ONLY A SINGLE TAPEWORM SHEEP HYDATID CYST FORMS IN TISSUE

HYDATID CYSTS FORM IN TISSUE

TISSUE WITH CYSTS RUPTURE CYST CAUSES TAPEWORMS INTO TISSUE DAMAGE TO INGESTED BY DOG RELEASE TAPEWORMS ORGANS

Figure 31-9. Echinococcus life cycle.

allergenic fluid. Optional treatment usually starts with References treatment for months with albendazole to kill the cysts (although this alone is rarely curative). The cyst is then Grove DI. Tissue Nematodes (Trichinosis, Dracunculiasis, Fi- exposed surgically and some of the cyst fluid is carefully lariasis. In: Mandell GL, Bennett JE, Dolin R. editors. Prin- aspirated. Saline, iodophors, or ethanol is next instilled ciples and Practice of Infectious Diseases. 4th edition. New York: Churchill Livingstone 1995;2531-2537. into the cyst to make sure the contents are dead. After King HK. Cestodes (tapeworms). In: Mandell GL, Bennett JE, about 30 minutes the cyst is cut out. Dolin R. editors. Principles and Practice of Infectious Dis- When a hydatid cyst is inoperable due to a tricky lo- eases. 4th edition. New York: Churchill Livingstone cation or a poor surgical candidate, therapy with alber- 1995;2544-2553. dazole is initiated and in some centers this is followed Liu LX, Weller PF. Drug therapy: Antiparasitic drugs. N Engl by CAT scan guided fine needle injection of ethanol into J Med 1996;334:1178-84. the cyst. Mahmoud AA. Trematodes (Schistosomiasis) and other Since dogs and sheep perpetuate the cycle, efforts to- flukes. In: Mandell GL, Bennett JE, Dolin R. editors. Prin- ward control should target these animals. Dogs in graz- ciples and Practice of Infectious Diseases. 4th edition. New ing countries should not be fed uncooked animal meat York: Churchill Livingstone 1995;2538-2544. and should be treated periodically with niclosamide. Rosenblatt JE. Antiparasitic Agents. Symposium On Antimi- crobial Agents-Part VII. Mayo Clin Proc 67:276-287, 1992. Fig. 31-10. Summary of the helminths. Sanford JP, Gilbert DN, et al. Guide To Antimicrobial Therapy 1996. Antimicrobial Therapy, Inc, Dallas Texas; 1996. Fig. 31-11. Summary of the anti-helminths drugs.

261 Figure 31-10 HELMINTHS Figure 31-10 (continued) M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple OMedMaster Figure 31-11 ANTI-HELMINTHS DRUGS M. Gladwin and B. Trattler, Clinical Microbiology Made Ridiculously Simple ©MedMaste CHAPTER 30. PROTOZOA

PART 4. PARASITES

CHAPTER 30. PROTOZOA

234 CHAPTER 30. PROTOZOA

NORMAL HOST

Entamoeba histolytica Giardia lamblia TROPHOZOITE TROPHOZOITE

BINUCLEATED PRECYST

NUCLEI GLYCOGEN VACUOLE CHROMATOID BODIES TETRANUCLEATED CYST

4 NUCLEI

Figure 30-1

It is estimated that 5% of U.S. adults harbor this or- 25% of Americans show serologic evidence of previous ganism, mostly asymptomatically. Outbreaks occur infection. It can cause outbreaks of diarrhea from when sewage contaminates drinking water. The organ- contaminated municipal water sources and in infants ism is also harbored by many rodents and beavers; in day care centers. Sporadic cases can occur in campers frequently develop Giadia abia infection travelers. after drinking from "clear" mountain streams. Cidi is ingested as a round oocyst that After ingestion of the cyst, Giadia abia converts contains 4 motile sporozoites. Its life cycle occurs to the trophozoite form and cruises down and adheres within the intestinal epithelial cells, and it causes di- to the small intestinal wall. The organism coats the arrhea and abdominal pain. These symptoms are self- small intestine, interfering with intestinal fat absorp- li miting in immunocompetent individuals. However, tion. The stools are therefore packed with fat, which has in immunocompromised patients (AIDS patients, can- a horrific odor! The patient will have a greasy, frothy cer patients, or organ transplant recipients who are diarrhea, along with abdominal gassy distension and receiving immunosuppressive therapy), this organism cramps. Since Giadia do NOT invade the intestinal causes a severe, protracted diarrhea that is life- wall, there is NO blood in the stool!!! threatening. These patients may have 3-17 liters of For diagnosis and control of Giardia: stool per day. Currently, there is no effective therapy. A new 1) Examination of stool for cysts or trophozoites. macrolide drug, azithromycin (see Chapter 17), is be- 2) Commercial immunoassay kit to detect Giardia ing studied. abia antigens in aqueous extracts of stool specimens. 3) Sanitation measures. Treat these patients with metronidazole (see Fig. Isospora and Microsporidia 30-2). These organisms cause a severe diarrhea in immunocompromised individuals. They are transmitted via the Cryptosporidium fecal-oral route. Fortunately, the combination of trimethoprim with sulfamethoxazole (see Chapter It is now apparent that this critter is everywhere! 19) is effective against Isospora, while albendazole Animals and humans are equally infected and about (see Chapter 31) can treat Microsporidia.

235 CHAPTER 30. PROTOZOA

236 CHAPTER 30. PROTOZOA

Figure 30-3

J 237 CHAPTER 30. PROTOZOA

Figure 30-4

238 CHAPTER 30. PROTOZOA

239 CHAPTER 30. PROTOZOA

Figure 30-6

240 Figure 30-7 CHAPTER 30. PROTOZOA

Figure 30-8 MALARIA

242 I CHAPTER 30. PROTOZOA

243 CHAPTER 30. PROTOZOA

Figure 30-10

244 CHAPTER 30. PROTOZOA

245 CHAPTER 30. PROTOZOA

246 CHAPTER 30. PROTOZOA

Figure 30-11

251 CHAPTER 31. HELMINTHS

Figure 31-1

252 CHAPTER 31. HELMINTHS

253 CHAPTER 31. HELMINTHS

Figure 31-2

254 CHAPTER 31. HELMINTHS

Figure 31-3

255 CHAPTER 31. HELMINTHS

256 CHAPTER 31. HELMINTHS

25 7 CHAPTER 31. HELMINTHS

Figure 31-6

258 CHAPTER 31. HELMINTHS

259 CHAPTER 31. HELMINTHS

HUMAN EATS CYSTICERCI PORK WITH u DEVELOP IN CYSTICERCI PIG MUSCLE

Figure 31-8. Pork tapeworm life cycle.

260

CHAPTER 31. HELMINTHS

_ HUMANS INGEST LARVAE MIGRATE EGGS INTO TISSUE

EGGS IN DOG SHEEP INGEST STOOL EGGS

LARVAE MIGRATE INTO TISSUE USUALLY ONLY A SINGLE TAPEWORM SHEEP HYDATID CYST FORMS IN TISSUE

HYDATID CYSTS FORM IN TISSUE

TISSUE WITH CYSTS RUPTURE CYST CAUSES TAPEWORMS INTO TISSUE DAMAGE TO INGESTED BY DOG RELEASE TAPEWORMS ORGANS

Figure 31-9. Echinococcus life cycle.

PART V. VERY STRANGE CRITTERS

CHAPTER 32. PRIONS (Proteinaceous Infectious Particles): Mad carnivorous cows, shaking cannibals, and a few good reasons to be a vegetarian. . .

Introduction: vocates for the protein-only theory find that the infectious agent consists only of prion proteins with little, if any, nu- The fancy name for Prion diseases is the transmissible cleic acid, whereas advocates for the viral theory argue spongiform encephalopathies (TSE); so named because that it remains possible for prions to contain extremely these diseases are transmissible and create spongiform small amounts, or protected, nucleic acid. pathological changes in the brain resulting in en- Laboratory data indicate that the prion protein (PrP) cephalopathy (i.e. causing brain damage). These diseases is the major (if not exclusive) component of prions. In are fatal neurodegenerative disorders of humans and short, prions are resistant to agents that modify nucleic other animals. The best known animal diseases are acids but susceptible to agents that modify proteins. scrapie in sheep and goats, and bovine spongiform en- The protein-onl hpothesis is the most widely ac- cephalopathy (BSE or mad cow disease) in cattle. cepted theory today. Four human prion diseases have been identified so far, all of which are VERY rare: Creutzfeldt-Jakob dis- If prions do not contain nucleic acids, how can they be ease (CJD), kuru ("shivering"), Gerstmann-Straussler- infectious? How do they replicate? What about the ge- Scheinker disease (GSS), and fatal familial insomnia (F F1). netic code dogma? Isnt it heretical to suggest that an agent without nucleic acids can replicate? Prion diseases share the following characteristics: Well, it turns out that PrP is encoded by an endogenous gene (for humans located on chromosome 20), but exists • Long incubation time (months to years) in two conformational isoforms, that is PrP has two dif- • Gradual increase in severity leading to death ferent (secondary and tertiary) protein structures: within months of onset • No host immune response • The cellular isoform of PrP is constitutively ex- • Non-inflammatory process in the brain pressed by normal animals, primarily in the brain • Neuro-pathological findings may include: and is called PrPC for cellular. The function of PrPC • Macroscopical examination is often normal. remains to be clarified. • Microscopical spongiform changes (small, appar- • The disease associated isoform of PrP is called PrP ently empty, microscopic vacuoles of varying sizes for scrapie. within the neural tissue), neuronal loss, and amyloid plaques (a pathological proteinaceous Whats the difference between the normal PrPC and substance deposited between cells) with accumu- PrPSC? Again, the conformation (that is structure) of lation of the prion protein (PrP). PrPSC is very different from PrPC, and is thought to be responsible for the development of disease: Aberrant me- Prion diseases are unique in being both inherited and tabolism of PrPSC results in accumulation of the protein infectious. There is also a sporadic manifestation with and brain injury. no obvious inherited or infectious etiology. However, The conformational change of PrPC is thought to be neural tissue from individuals affected by either inher- post-translational, and can apparently be induced by ited or sporadic (as well as infectious) form of prion dis- the presence of PrPSC, maybe with the interaction of eases is infectious! other proteins. Thereby a small amount of PrPSC will initiate a chain-reaction of conformational change of The Infectious Agent and Etiology: PrPC into PrPSC (see Fig. 32-1). This is the clue to the above raised question about The nature of the infectious agent is still under investi- replication of the prions if the infectious particles do not gation and debate. Briefly, two main theories are debated: contain nucleic acids. The prions do not need the genetic The protein-onl hpothesis and the viral hpothesis. Ad- software in the infectious particle-its already present

265 CHAPTER 32. PRIONS

Figure 32-1

266

CHAPTER 32. PRIONS

in the host as part of the genome! The amino acid se- ing the diseased). Kuru gradually disappeared after quence of the "sick" isoform of PrP (PrPSC) accumulating the cessation of this practice. One can speculate in a patients brain is encoded by the PrP gene of that whether that epidemic originated with an index particular individual! case of sporadic Creutzfeldt-Jakob disease (sCJD). • Iatrogenic cases of Creutzfeldt-Jakob disease (CJD) Dr. Stanley B Prusiner proposed the name prion for have been established through contaminated the agent causing transmissible spongiform en- (neuro) surgical instruments, dural and corneal grafts and administration of cadaveric pituitary cephalopathy to emphasize the nature of these proteina-ceous infectious particles, and later concluded that the hormones. infectious agent is PrP. He was awarded the Nobel Prize in Physiology or Medicine in 97 for the discovery Clinical Presentation: of prions. Until the mad cow disease epidemic in the UK in the Basically three different etiologies are thought to be early 1990s causing human new variant Creutzfeldt- involved relating to the nature of the disease: Jakob disease (vCJD), prion diseases were widely unknown to many physicians. The human prion diseases • Inherited: Mutations in PrP gene favoring sponta- are still VERY rare. Due to the large number of infected neous conformational change to PrPSC. The disease cattle which have entered the human food-chain and the is following an autosomal dominant pattern. possible long incubation time, it remains to be seen • Infectious: Exogenous PrPSc inducing conforma- whether the new variant Creutzfeldt-Jakob disease tional change of host PrPC into PrPSC. (vCJD) will turn into an epidemic. • Sporadic: Unknown; probably spontaneous conver- The prion diseases share many clinical features; all are sion of wild-type PrP or rare de novo mutations in characterized by neurological signs and symptoms: PrP gene leading to the conformational change to PrPS~. • Rapidly progressive dementia • Psychiatric symptoms • Cerebellar symptoms (e.g. ataxia) Transmission and Epidemiology: • Involuntary movements (e.g. myoclonic jerks, choreathetosis) Contaminated neural tissue has been shown to trans- • Ultimately fatal disease mit disease-even from species to other (i.e. crossing the "species-barrier", e.g. sheep to cattle, cattle to human Please refer to Fig. 32-2 for key features of individual etc). The route of transmission can be inoculation but diseases. also oral. This has significant implications for the epidemiology of the disease. Diagnosis: Infectivity of other tissues and body fluids (e.g. blood) are under investigation. The infectious particles are rela- • The gold standard for diagnosis of prion diseases is tively resistant to heat and many commonly used chem- histopathologic examination and immunostaining ical disinfectants as well as irradiation. for PrPSC of brain tissue. • Cerebro-spinal fluid (CSF) is normal except that • The bovine spongiform encephalopathy (BSE) epi- mildly elevated protein levels may be seen. Eleva- demic among cattle is attributed to the practice of tion of certain proteins (14-3-3 and S100 proteins) feeding cattle (contaminated) sheep offal (the nice may occur in the cerebro-spinal fluid (CSF) as wording is meat and bone meal), which basically is well as in serum (S100 protein), but this is not spe- the remainder of a butchered animal (bones etc), ac- cific for prion diseases and the utility remains to tually turning cattle into carnivores. This practice be established. has now been widely banned, although animal offal • Neuro-imaging tests (CT and MRI) may be normal, are still fed to other livestock than cattle. Ulti- and abnormal findings are generally not diagnostic. mately, transmission of the disease from mad cows • Serial EEG can be very helpful in the diagnosis of to humans causing a variant of Creutzfeldt-Jakob Creutzfieldt-Jakob disease. An abnormal pattern disease (new variant Creutzfeldt-Jakob disease, (period sharp wave complexes) are ultimately seen vCJD) has been established. Sale of meat on the in more than 2/3 of Creutzfeldt-Jakob disease pa- bone (e.g. T-bone steaks) has been banned to reduce tients. However, this abnormality is generally NOT the contamination risk from neural tissue. seen in new variant Creutzfeldt-Jakob disease. • The kuru epidemic among the Fore population • PrP is also present in lymphoreticular tissue, and of Papua New Guinea was probably transmitted the utility of tonsil and spleen biopsies are under in- through ritualistic cannibalism (as a rite of mourn- vestigation as diagnostic tools.

267 CHAPTER 32. PRIONS

Figure 32-2

Treatment: Chesebro B. Prion Protein and the Transmissible Spongiform Encephalopathy Diseases. Neuron 1999; 24:503-506. Unfortunately, this paragraph is going to be very short. Gajdusek DC, Zigas V. Degenerative Disease of the Central No curative treatment is currently available. Nervous System in New Guinea. N Engl J Med 1957; 257: 974-978. Recommended Reviews: Gajdusek DC. Unconventional Viruses and the Origin and Disappearance of Kuru. Science 1977; 197:943-960. Belay ED. Transmissible Spongiform Encephalopathies in Harris DA. Prion Diseases. Nutrition 2000; 16:554-556. Humans. Annu Rev Microbiol (1999) 53;283-314. Johnson RT, Gibbs CJ. Creutzfeldt-Jakob Disease and Re- Johnson RT, Gibbs CJ. Creutzfeldt-Jakob Disease and Re- lated Transmissible Spongiform Encephalopathies. N Engl lated Transmissible Spongiform Encephalopathies. NEJM J Med 1998; 339:1994-2004. ( 1998)339;1994-2004. Prusiner SB. Novel Proteinaceous Infectious Particles cause Prusiner SB. Prions. PNAS (1998) 95;13363-13383. Scrapie. Science 1982; 216:136-144. Tyler KL. Prions and Prion Diseases of the Central Nervous Sys- Prusiner SB. Molecular Biology and Genetics of Neurodegen- tem (Transmissible Neurodegenerative Diseases). In Man- erative Diseases caused by prions. Adv Virus Res 1992; dell et al. Principles and Practice of Infectious Diseases 5th 41:241-280. edition Churchill Livingstone (2000) pp. 1971-1980. Prusiner SB. Prions. PNAS 1998; 95:13363-13383. Scott MR et al. Compelling Transgenic Evidence for Trans- Bibliography: mission of Bovine Spongiform Encephalopathy Prions to Humans. PNAS 1999; 96:15137-15142. Belay ED. Transmissible Spongiform Encephalopathies in Tyler KL. Prions and Prion Diseases of the Central Nervous Humans. Annu Rev Microbiol 1999; 53:283-314. System (Transmissible Neurodegenerative Diseases). In Bruce ME et al. Transmissions to Mice indicate that °New Mandell et al. Principles and Practice of Infectious Diseases Variant" CJD is caused by the BSE agent. Nature 1997; 5th edition Churchill Livingstone 2000; pp. 1971-1980. 389:498-501.

268

Chae 33. ONE STEP TOWARDS THE POST-ANTIBIOTIC ERA?

DEVELOPMENT AND SPREAD OF MECHANISM OF BACTERIAL ANTIMICROBIAL RESISTANCE GENETIC VARIABILITY

Wih he ce ideead ee of aibi- Geeic aiabii i eeia i de f icbia ic, e ae fcig baceia geeica chage ei cc. Thee ae 3 baic echai f ie. Thi aibiic Daii ha ed e- geeic aiabii eadig eiace ag baceia. high eia ai f baceia ha heae I1 Pi ai a cc i a ceide bae ceae a P-Aibiic Ea. Seea fac ae a- ai, hich i efeed a iceia ciaed ih eegece f eiace ag gai. chage. Thee ai a ae he age ie f These fac icde: a aiicbia age, iefeig ih i acii. 2) Maceia chage e i e- 1) Wideead, iaiae e f bad-ec aagee f age ege f DNA a a aibiic, eecia i dacae cee ad ICU. ige ee. Thee eaagee a icde (e.g. eae f ia iee ih aibiic). iei, dicai, iei, deei 2) Ue f aibiic i aia hbad ad fiheie aii f age eece f DNA f e ee ifeci ad iceae aia gh. cai f a baceia che ahe. 3) Eceie e f aiicbia eaai i 3) Aciii of feig DNA caied b aid, a ad ceaig i i -heahcae baceihage aabe geeic eee (ee faciiie. Chae 3). Thee feig eee gie he ga- 4) Iceaed be f icied a- i he abii ada aiicbia acii. ie eiig ged ce f aibiic. 5) Pged ia f debiiaed aie. 6) Ieaia ae ig he ee f e- MECHANISMS OF ANTIMICROBIAL ia baceia (e.g. Mcobacterium tuberculosis). RESISTANCE 7) Pe eadig iadeae aibiic age becae f he iceaig eee f adeae a- Thi geeic aiabii ca be fhe eaaed i iicbia hea. e ecific eiace echai. Thee echa- i f eiace ae a f: Fig. 33-1. decibe eig-ecific cibig fac 1) Eaic ihibii f aibiic eadig a- ad eia ai dced i e deai. ibiic iacii. F eaiig aiicbia eiace ed ad 2) Aeai of baceia ebae e- bea, hee ae ceai icie ha cie e e f aibiic i baceia. hd e. Fi, gie fficie ie ad dg e, 3) Pi of aibiic eff hich acie aiicbia eiace i eege. Thee ae ai- he aibiic f he baceia. icbia hich eiace ha eea a- 4) Aeai of baceia ei age hich eaed. Secd, he deee f eiace i ae hee age ecgiabe aibiic. geie, eig f ee hgh iee- Secific eae icde: diae high ee. The ecei he e i he di- • Aeai f iba age ie ec afe f geeic ifai b aid • Aeai of ce a ec age a, hich ca e i iediae high ee e- • Aeai of ciica ee iace. Thid, gai ha ae eia e 5) Ba of aibiic ihibii aig bace- dg ae ie bece eia he. C- ia fid aeae aha ie he e eiace ag a ca f dg eiace - aha i bced b a aibiic. ie cae f aibiic ae bh ibe (e.g. Seccc pneumoniae). Fh, ce eiace a- Eaic Ihibii ea, i i ie decie , if a a. Fifh, he e f aiicbia b a e e affec he i he Eaic ihibii i e f he c eeded a e a he iediae eie. de f aiicbia eiace. F eae,

269 CHAPTER 33. ONE STEP TOWARDS THE POSTANTIBIOTIC ERA?

Figure 33-1 CHAPTER 33. ONE STEP TOWARDS THE POST-ANTIBIOTIC ERA?

Staphylococcus aureus resistance to beta-lactam an- glycosides, may result from alteration of ribosomal tibiotics (e.g. penicillin) is due mainly to the production binding sites. Failure of the antibiotic to bind to its tar- of beta-lactamases, enzymes that inactivate these an- get sites on the ribosome disrupts its ability to inhibit tibiotics by splitting the beta-lactam ring. Enterococci protein synthesis and cell growth. Ribosomal resistance and gram-negative bacilli resistance to aminoglycosides to streptomycin may be significant but is fairly uncom- is also commonly due to modifying enzymes that are mon with gentamicin, tobramycin and amikacin. Ribo- coded by genes on plasmids or the chromosome. somal resistance can also be associated with decreased intracellular accumulation of the drug. Examples in- Alterations of Bacterial Membranes clude Staphylococcus aureus and Enterococci species re- istance to macrolides. Outer Membrane Permeability: Many penicillins have activity against gram-positive bacteria but not against gram-negative bacteria because gram-negative bacteria Alterations of Cell Wall Precursor Targets: Resis- have a lipid bilayer that acts as a barrier to the penetra- tance of Enterococci to vancomycin has been classified tion of antibiotics into the cell. Only when these penicillins as A, B, or C based on levels of resistance. Class A re- are able to get inside the cell are they able to work. Passage sistance is considered high level resistance and is asso- of hydrophilic (water-soluble) antibiotics through this ciated with the vanA gene. The vanA gene is carried on outer membrane is facilitated by the presence of porins, a plasmid and encodes an inducible protein that is in- proteins that form water-filled diffusion channels through volved in cell wall synthesis in E. Coli. These proteins which antibiotics can travel. Mutations resulting in the are responsible for synthesizing peptidoglycan precur- loss of specific porins can occur and may lead to increased sors that have a different amino acid sequence from the resistance to penicillins. Pseudomonas aeruginosa resis- normal cell wall peptidoglycan. This newly modified tance to imipenem is a perfect example of this mechanism. peptidoglycan binds glycopeptide antibiotics with reduced affinity, thus leading to resistance to vancomycin Inner Membrane Permeability: Aminoglycosides re- and teicoplanin. Classes B (vanB) and C (vanC) resis- quire active electron transport ("proton motive force") tance phenotypes are considered to have moderate which means that a positively charged aminoglycoside and low-level resistance respectively. The recent detec- molecule is "pulled" across cytoplasmic membranes of the tion of decreased susceptibility to vancomycin among internal negatively charged cell. The energy generation or Staph yloccus aureus is also quite scary. Improvements the proton motive force that is required for substrate trans- are being made in the ability of clinical laboratories to port into the cell may be altered in mutants resistant to characterize these resistant isolates. aminoglycosides. Staphylococcus resistant to aminoglycosides is an example. These aminoglycoside-resistant or- Alterations of Critical Enzymes: Beta-lactam anti- ganisms with altered proton motive force occur rarely, but biotics inhibit bacteria by binding covalently to penicillin develop in the course of long-term aminoglycoside therapy. binding proteins (PBPs) also called transpeptidases (see Page 114) in the cytoplasmic membrane. These target pro- Promotion of Antibiotic Efflux teins are necessary for the synthesis of the peptidoglycan that forms the cell wall of bacteria. Alterations of PBPs that The primary mechanism for decreased accumulation of prevent successful binding can lead to beta-lactam resis- tetracycline is due mainly to active efflux of the antibiotic tance. In gram-positive bacteria, resistance to beta-lactam across the cell membrane. Decreased uptake of tetracy- antibiotics may be associated either with a decrease in the cline from outside the cell also accounts for decreased affinity of the PBP for the antibiotic or with a decrease in accumulation of tetracycline inside resistant cells. Tetra- the number of PBPs produced by the bacterium. cycline resistance genes are generally inducible by subtherapeutic concentrations of tetracycline which emphasizes the importance of adequate dosing. Pseudomonas Bypass of Antibiotic Inhibition aeruginosa and Staphylococcus aureus are bugs that display this type of resistance to tetracycline. This system Another mechanism for acquiring resistance to specific may also represent a potential mechanism of resistance to antibiotics is by the development of auxotrophs, which the newer quinolones, but has not been found to be com- have growth factor requirements different from those mon among quinolone-resistant clinical isolates. of the wild strain. These mutants require substrates that normally are synthesized by the target enzymes, Alterations of Bacterial Protein Targets and thus, if the enzyme is blocked and the substrates are present in the environment, the organisms are Alterations of Ribosomal Target Sites: Resistance able to grow despite inhibition of the synthetic enzyme. to a wide variety of antiribosomal agents, including This is particularly concerning because the bacteria is tetracyclines, macrolides, clindamycin, and the amino- able to create additional pathways to meet growth

271 CHAPTER 33. ONE STEP TOWARDS THE POST-ANTIBIOTIC ERA?

Table 33-2

272 CHAPTER 33. ONE STEP TOWARDS THE POST-ANTIBIOTIC ERA? requirements in response to a particular pathway being sounds really simple, but proper and adequate blocked by the antibiotic. For example, "thymidine de- handwashing by healthcare professionals can pre- pendent" bacteria like enterococci are able to utilize vent many cases of infection due to virulent and exogenous supplies of thymidine for enzyme activity antibiotic-resistant pathogens. and are thus highly resistant to trimethoprim which 5) Utilize education to achieve therapeutic and pre- blocks endogenous production of thymidine by bacterial ventative goals. Patients and families should be enzymes. counseled as to when antibiotics are needed, how to take them correctly and for the proper duration. Education can also be used to foster earlier DECREASING ANTIMICROBIAL detection of therapeutic failure, which may be critical when treating patients who may be in- RESISTANCE fected with antibiotic-resistant pathogens. Our In order to minimize antibiotic resistance in your pa- communities must be cautioned against buying tients you must employ these resistance management cleaning products with antimicrobial properties as approaches: well as using feed lot antibiotics.

1) Withhold antibiotics in situations where they References are not likely to benefit the patient for self-limited viral infections such as "the common cold". Symp- Elliott TSJ, Lambert PA. Antibacterial Resistance in the In- tomatic treatment and supportive measures are tensive Care Unit: Mechanisms and Management. British the most appropriate care and antibacterial agents Medical Bulletin 55:259-276, 1999. Fridkin SK, Gaynes RP. Antimicrobial Resistance in Inten- are not indicated. sive Care Units. Clinics in Chest Medicine 20:303-16, 1999. 2) Use the narrowest spectrum antimicrobial Jones, RN. The Impact of Antimicrobial Resistance: Changing agent possible to treat an infection. For example, Epidemiology of Community-acquired Respiratory-tract In- a semisynthetic penicillin or even oral penicillin fections. Am J Health-Syst Pharm 56:S4-S11, 1999. would be a much better choice for treatment of a Liu HH. Antibiotic Resistance in Bacteria: A Current and Fu- staphylococcal infection than a broad spectrum ture Problem. RheumaDerm 1999; 59:387-396. fluoroquinolone or cephalosporin. This works well Mayer KH, Opal SM, Medeiros AA. Mechanisms of Antibiotic provided the organism is known or likely to be sus- Resistance. Basic Principles in the Diagnosis and Manage- ceptible to the narrower spectrum antibiotic. ment of Infectious Diseases 2000; 15:236-252. 3) Base decisions about broadness of empiric Neely AN, Holder IA. Antimicrobial Resistance. Burns 25:17-24, 1999. antibiotic coverage on the severity of illness. Reece SM. The Emerging Threat of Antimicrobial Resistance: For example, in the case of a patient who is clini- Strategies for Change. The Nurse Practitioner 24:70-86, cally stable and not at risk for significant morbidity 1999. if a resistant pathogen is not treated immediately, Virk A, Steckelberg JM. Clinical Aspects of Antimicrobial Re- it may be appropriate to begin a narrow spectrum sistance. Symposium on antimicrobial agents. Mayo Clin agent while awaiting culture and susceptibility Proc 2000; 75:200-214. data. 4) Emphasize prevention of infection through careful hygiene, especially handwashing and other measures to control the spread of pathogens. It

273 INDEX

3TC, 231 atovaquone, 250 A subunit, 12 atypical Mycobacteria, 106 abacavir, 227, 232 Augmentin, 117 ABCD, 155 autotrophs, 7 ABLC, 155 azidodideoxythymidine (AZT), 225 abscess, 36 azithromycin, 235 Acanthamoeba, 237 AZT, 202, 225 acid-fast stain, 106 aztreonam, 122 acquired immunodeficiency syndrome, 192, 198 B subunit, 12 actinomycetes, 151 B-cell lymphoma, 200 acute post-streptococcal glomerulonephritis, 25 Babesiosis, 244 acyclovir, 231 bacillary angiomatosis, 88 adenoviridae, 210 bacilli, 4 adhesins, 8 Bacillus, 38 aerobes, 6 B , 38 aerotolerant anaerobes, 7 B , 39 aflatoxin, 151 bacteremia, 12 African sleeping sickness, 246 Bacteroides fragilis, 64 AIDS related complex, 196 Bacteroides melaninogenicus, 65 AIDS, 192, 198 B , 248 albendazole, 235 B , 88 alpha-hemolytic streptococci, 22 B , 88 amantadine, 175, 229, 232 basal body, 8 amastigotes, 245 BCG vaccine, 104 Ambisome, 156 beef tapeworm, 259 amikacin, 128 Bejel, 95 aminoglycosides, 128 benznidazole treatment, 248 aminopenicillins, 116 beta-hemolytic streptococci, 22 amoxicillin, 116 beta-lactam ring, 114 amphoteracin B, 144, 155 beta-lactamase inhibitors, 117 Amphotericin B colloidal dispersion, 155 BK polyomavirus, 210 Amphotericin B lipid complex, 155 Blastomyces, 147 amphotericin B deoxycholate, 156 Bordet-Gengou medium, 70 ampicillin, 116 B , 69 amprenavir, 228, 232 B , 96 anaerobic gram-positive cocci, 65 B , 98 A , 252 botulism, 39 anergy, 140 bovine spongiform encephalopathy, 265 anthrax, 38 Branhamella catarrhalis, 52 anti-C5a peptidase, 23 Brill-Zinsser disease, 87 anti-viral medications, 224 Brucella, 75 antigenic drift, 173, 174 B , 255 antimetabolites, 141 bubonic plague, 73 arboviruses, 214 bunyaviridae, 216 ARC, 196 Burkitts lymphoma, 207 ArgyII-Robertson pupil, 93 C carbohydrate, 22 artemether, 240, 250 CA proteins, 193 artesunate, 250 calcium alginate swab, 70 A , 251 Caliciviridae, 219 aspergilloma, 151 California encephalitis, 216 aspergillosis, 151 C , 62 Aspergillus flavus, 151 C , 63 athletes foot, 145 Candida albicans, 146, 150, 200

27,5 INDEX candidiasis, 150 condyloma latum, 91 capsid proteins, 193 cord factor, 102 capsid, 16, 161, 163 core polysaccharide, 3 capsomer, 163 Coronaviridae, 219 capsule b, 68 Corynebacterium, 45 capsules, 9 Corynebacterium diphtheriae, 45 carboxypenicillins, 117 Coxiella burnetti, 88 carbuncle, 36 Coxsackie A and B, 218 Carol Burnett, 89 creeping eruption, 256 caseous necrosis, 104 Creutzfeldt-Jakob disease, 265 cat-scratch fever, 88 croup, 175 catalase, 6 cryptococcosis, 149 catalase reaction, 22, 31 Cryptococcus neoformans, 149, 200 cefpodoxine, 120 Cryptosporidium, 235, 237 ceftriaxone, 131 cutaneous larval migrans, 256 cell wall, 3 Cyclospora cayetanensis, 234, 249 cellulitis, 36 cysticercus, 259 cephalosporins, 117 cytomegalovirus, 200, 206 cercariae, 257 d4T, 202, 227 cestodes, 256 dalfopristin, 27 Chagas disease, 247 Dane particle, 184 chagoma, 247 darkfield microscope, 5 chemoheterotrophs, 7 ddC, 195, 202, 228, 231 chemotaxis, 8 ddl, 195, 202, 231 chickenpox, 205 delaviridine, 228, 232 C , 83 Dengue fever, 216 C , 83 Dermacentor andersoni, 85 C , 79 Dermacentor variabilis , 85 Chlamydia, 78 dermatophytoses, 145 chloramphenicol, 126 dicloxacillin, 116 chloroquine, 243 didanosine, 195, 202, 225, 227, 231 cholera, 62 dideoxycytidine, (ddC), 202, 228, 232 choleragen, 62 dideoxyinosine, (ddl), 202, 231 chromoblastomycosis, 146 diethylcarbamazine treatment, 256 chromotoid bodies, 234 dimorphic fungi, 144 ciprofloxacin (Cipro), 139 dimyristoylphosphatidylcholines, 155 CKR5, 196 dimyristoylphosphatidylglycerols, 155 Cladosporium, 156 Diphyllobothrium latum, 259 clarithromycin, 67, 127 distearoylphosphatidylglycerol, 156 clavulinic acid, 117 DNA viruses, 162, 166, 168 clindamycin, 127 DNAases, 23 clofazimine, 136 DPT, 41 Clostridium, 38, 39 Dracunculus medinensis, 256 C Duffy antigens, 242 C , 42 dwarf tapeworm, 256 C , 42 Ebola virus, 221, 223 C , 40 Echinococcus granulosus, 260 cloxacillin, 116 echoviruses, 218 clue cells, metronidazole, 69 edema factor, 39 CMV retinitis, 226 efavirenz, 228, 232 CMV, 200, 206 Ehrlichia canis, 88 coagulase, 31, 32 Ehrlichia chaffeensis, 88 cocci, 4 Ehrlichiosis, 88 Coccidioides immitis, 200 elementary body, 79 cold agglutinins, 111 elephantiasis, 255 complement fixation test, 111 ELISA test, 201

276 INDEX

EMB agar, 54 Francisella tularensis, 74 Embden-Meyerhof pathway, 7 FTA-ABS test, 95 endotoxins, 4, 12, 50 fungal antibiotics, 155 endospores, 10 fungi, 144 E , 234 furuncle, 36 enterics, 54 fusin, 196 Enterobacteriaceae, 56 fusion protein, 175 E , 254 Fusobacterium, 65 enterotest, 249 gag, 194 enterotoxins, 11, 32 gametocytes, 242 Enterobacter, 57 gamma-hemolytic streptococci, 22 enterovirus, 217 ganciclovir, 224, 225 env, 194 G , 69 envelope, viral, 164 gas gangrene, 42 epimastigotes, 245 generalized transduction, 18 Epstein-Barr virus, 200, 206, 207 genciclovir, 231 ergosterol in fungi, 144 Gerstmann-Straussler-Scheinker disease, 265 erythema chronicum migrans, 97 gentamicin, 128 erythema infectiosum, 212 Ghon complex, 105 erythema marginatum, 24 Ghon focus, 105 erythema nodosum leprosum, 136 G , 234 erythrocytic cycle, malaria, 242 glomerulonephritis, 25 erythrogenic toxin, 23 gonorrhoeae, 51 erythromycin, 127 gp120, 193 Escherichia coli, 56 gp41, 193 eucaryotes, 5 gram stain, 1 exfoliatin, 32 gram-negative cell, 2, 5 exo-erythrocytic cycle, malaria, 242 gram-positive cell, 2, 4 exosporium, 11 griseofulvin, 155, 157 exotoxins, 11 group antigen, 194 extra cytoplasmic adenylate cyclase, 70 group B streptococci, 25 F protein, 175 group D streptococci, 27 F plasmids, 20 Guinea worm, 256 F-plasmid, 19 gummas, 92 F1 virulence factor, 73 H antigen, 55 facultative anaerobes, 6 H subunit, 12 facultative intracellular organisms, 11 H , 69 famciclovir, 231 H , 69 fatal familial insomnia, 265 H, , 68 fermentation, 7 Hansens disease, 107 Fifth disease, 212 hantavirus pulmonary syndrome, 216 filamentous hemagglutinin (FHA), 70 heat-labile toxin, 39 filariae, 254 heat-stable toxin, 39 fimbriae, 8 helical symmetry capsids, 164 fimbrial antigens, 71 H , 63 fish tapeworm, 259 helminths, 247 Fitz-Hugh-Curtis syndrome, 83 hemagglutinin, 172 flagella, 8 hemolysins, 32 flatworms, 256 hemolytic uremic syndrome, 56 flaviviridae, 216 hemorrhagic fever, 216 flesh-eating streptococcus, 24 hepatitis A virus, 180 flucloxacillin 116 hepatitis B virus, 182 fluconazole, 157 hepatitis C virus, 188 flukes, 256 hepatitis E virus, 188 fluoroquinolone antibiotics, 139 hepatitis delta virus, 187 foscarnet, 231 hepatitis, viral, 180

277 INDEX candidiasis, 150 condyloma latum, 91 capsid proteins, 193 cord factor, 102 capsid, 16, 161, 163 core polysaccharide, 3 capsomer, 163 Coronaviridae, 219 capsule b, 68 Corynebacterium, 45 capsules, 9 Corynebacterium diphtheriae, 45 carboxypenicillins, 117 Coxiella burnetti, 88 carbuncle, 36 Coxsackie A and B, 218 Carol Burnett, 89 creeping eruption, 256 caseous necrosis, 104 Creutzfeldt-Jakob disease, 265 cat-scratch fever, 88 croup, 175 catalase, 6 cryptococcosis, 149 catalase reaction, 22, 31 Cryptococcus neoformans, 149, 200 cefpodoxine, 120 Cryptosporidium, 235, 237 ceftriaxone, 131 cutaneous larval migrans, 256 cell wall, 3 Cyclospora cayetanensis, 234, 249 cellulitis, 36 cysticercus, 259 cephalosporins, 117 cytomegalovirus, 200, 206 cercariae, 257 d4T, 202, 227 cestodes, 256 dalfopristin, 27 Chagas disease, 247 Dane particle, 184 chagoma, 247 darkfield microscope, 5 chemoheterotrophs, 7 ddC, 195, 202, 228, 231 chemotaxis, 8 ddl, 195, 202, 231 chickenpox, 205 delaviridine, 228, 232 C , 83 Dengue fever, 216 C , 83 Dermacentor andersoni, 85 C , 79 Dermacentor variabilis , 85 Chlamydia, 78 dermatophytoses, 145 chloramphenicol, 126 dicloxacillin, 116 chloroquine, 243 didanosine, 195, 202, 225, 227, 231 cholera, 62 dideoxycytidine, (ddC), 202, 228, 232 choleragen, 62 dideoxyinosine, (ddl), 202, 231 chromoblastomycosis, 146 diethylcarbamazine treatment, 256 chromotoid bodies, 234 dimorphic fungi, 144 ciprofloxacin (Cipro), 139 dimyristoylphosphatidylcholines, 155 CKR5, 196 dimyristoylphosphatidylglycerols, 155 Cladosporium, 156 Diphyllobothrium latum, 259 clarithromycin, 67, 127 distearoylphosphatidylglycerol, 156 clavulinic acid, 117 DNA viruses, 162, 166, 168 clindamycin, 127 DNAases, 23 clofazimine, 136 DPT, 41 Clostridium, 38, 39 Dracunculus medinensis, 256 C Duffy antigens, 242 C , 42 dwarf tapeworm, 256 C , 42 Ebola virus, 221, 223 C , 40 Echinococcus granulosus, 260 cloxacillin, 116 echoviruses, 218 clue cells, metronidazole, 69 edema factor, 39 CMV retinitis, 226 efavirenz, 228, 232 CMV, 200, 206 Ehrlichia canis, 88 coagulase, 31, 32 Ehrlichia chaffeensis, 88 cocci, 4 Ehrlichiosis, 88 Coccidioides immitis, 200 elementary body, 79 cold agglutinins, 111 elephantiasis, 255 complement fixation test, 111 ELISA test, 201

276 INDEX

277 INDEX herpes simplex, 200, 204 lepromin skin test, 109 herpes zoster, 200 leprosy treatment, 135 heterophil antibody, 207 leprosy, 107 heterotrophs, 7 Leptospira, 99 Hfr cell, 19 lethal factor, 39 HHV-8, 200, 207, 208 leukocidins, 32 H , 200 lipase, 32 Histoplasma, 147 lipid A, 4 HIV, 192 Liposomal amphotericin B, 156 HIV prophylaxis, 229 Listeria monocytogenes, 45 HLA-DR (1 + 4), 98 Listeria, 45 hookworm, 249 lockjaw, 41 Hutchinsons teeth, 93 Loefflers medium, 45 hyaluronidase, 23, 32 long terminal repeat sequences, 193 hydatid disease, 260 LPS, 3, 50 Hymenolipis nana, 260 LTRs, 193 hyphae, 144 Lyme disease, 96 hypnozoites, 242 Lymphogranuloma venereum, 83 icosahedral symmetry capsids, 163 lysogenic conversion, 19 IgA1 protease, 50 lysogenic immunity, 17 imidazoles, 157 M protein, 22, 172 imipenem, 120 MacConkey agar, 54 impetigo, 36 mad cow disease, 265 inclusion conjunctivitis, 81 MAI, 106, 200 India ink stain, 10, 144 malaria, 240 indinavir, 202, 228, 232 Marburg virus, 221, 223 influenza, 173 measles virus, 176 initial body, 79 mebendazole treatment, 254 interferon, 230, 233 mefloquine, 243 interferon alpha, 187 melarsoprol, 250 interleukin-1, 12 meningitis, 50 interleukin-2, 229 meningococcal disease, 50 Intralipid, 156 merozoites, 242 isoniazid, 133 methicillin, 116 I, 235, 237 methicillin-resistant staphylococcus aureus, 36 Isospora, 233 metronidazole, 234, 236 itraconazole, 155, 157 microaerophilic bacteria, 7 ivermectin treatment, 255 microfilariae, 254 Ixodes ticks, 96 M, 235 Jarisch-Herheimer phenomenon, 95 MIP1-Alpha, 196 JC polyomavirus, 210 MIP1-Beta, 196 jock itch, 145 MMR vaccine, 175 K antigen, 55 molds, 144 kala-azar, 246 molecular mimicry, 257 Kaposis sarcoma, 200 molluscum contagiosum, 209 Katayama fever, 257 mononucleosis, 206, 207 ketoconazole, 144, 157 Monospot test, 207 K , 57 mumps virus 175 Kopliks spots, 176 murein lipoprotein, 2 L subunit, 12 mycelia, 144 lamivudine, 187, 195, 202, 227, 231 mycobacteria, 5 L , 72 Mycobacterium avium-intracellulare, 106, 110, 200 Legionnaires pneumonia, 71 Mycobacterium avium-complex, 106, 110, 200 Leishmania, 245 Mycobacterium chelonei, 110 leishmaniasis, 240 Mycobacterium fortuitum, 110 leonine facies, 109 Mycobacterium kansasii, 110

278 INDEX

Mycobacterium leprae, 107 parasites, 230 Mycobacterium marinum, 110 Parvoviridae, 166, 212 Mycobacterium scrofulaceum, 110 Pasteurella multocida, 76 Mycobacterium tuberculosis, 102, 200 PCP, 200, 235 Mycobacterium ulcerans, 110 pelvic inflammatory disease, 51 mycolic acid, 102 penicillin, 114 mycoplasma, 5 penicillin G, 115 Mycoplasma pneumoniae, 111 penicillin V, 115 mycoside, 102 penicillinase, 32, 115 mycotoxins, 151 pentamidine, 250 myonecrosis, 42 peptidoglycan layer, 1, 3 Naegleria fowleri, 237 peroxidase, 6 nafcillin, 116 pertactin, 71 NC proteins, 193 Pertussis toxin, 69, 70 Necator americanus, 251 Phialophora, 146 necrotizing fasciitis, 23, 24 picornaviridae, 217 nef, 194 pili, 8 Negri bodies, 220 pinta, 96 Neisseria catarrhalis, 52 pinworm, 254 Neisseria gonorrhoeae, 51 piperacillin, 117 Neisseria meningitidis, 50 pityriasis versicolor, 144 nelfinavir, 228, 232 plasmodia, 240 nematodes, 251 platyhelminthes, 256 neomycin, 128 pleomorphic bacteria, 4 neuraminidase, 172 Pneumocystis carinii, 238, 239 neuroaminidase inhibitors, 229 Pneumocystis carinii pneumonia, 200 neurotoxins, 11 pol, 194 nevirapine, 202, 228, 232 poliovirus, 217 new enteroviruses, 218 polyomavirus, 210 niclosamide treatment, 258 Pontiac fever, 71 nifurtimox treatment, 248, 250 porin, 3 NNRTIs, 227 pork tapeworm, 258 nocardia, 151 potassium iodide, antifungal, 158 nocturnal periodicity, 256 Potts disease, 106 Norwalk virus, 219 poxviridae, 166, 209 nucleocapsid protein, 172, 193 PPD skin test, 104 nystatin, 144, 155, 157 praziquantel, 257 O antigen, 3, 55 primaquine, 243 0-specific side chain, 3 prions, 265 obligate aerobes, 6 pristinomycins, 27 obligate anaerobes, 7 procaryotes, 5 omeprazole, 67 proglottids, 258 Onchocerca volvulus, 255 progressive multifocal leukoencephalopathy, 210 oncogenes, vira1190 promastigotes, 245 onychomycosis, 145 prophage, 17 opportunistic infections, 200 protease, 193, 194 optochin sensitivity, 27 protease inhibitor, 228, 232 oral hairy leukoplakia, 200 protective antigen, 39 Orthomyxoviridae, 172 protein A, 32 oseltamivir, 229, 232 Proteus and Rickettsia, 57 oxacillin, 116 Proteus mirabilis, 57 p24, 193 protozoa, 234 papilloma virus, 209 pseudomembrane, 45 papovaviridae, 209 pseudomembranous colitis, 127 parainfluenza virus, 175 pseudomembranous enterocolitis, 42 paramyxoviridae, 175 Pseudomonas aeruginosa, 63

279 INDEX

P , 64 schizont, 242 psittacosis, 83 scolex, 258 pyrantel pamoate treatment, 254 scotch tape test, 254 pyrazinamide, 134 scrapie, 265 pyrimethamine, 250 scrofula, 106 Q fever, 88 scrub typhus, 87 Quellung reaction, 10, 27 self-transmissible plasmid, 19 quinine, 239 sepsis, 12 quinolone, 131 septic shock, 12 quinupristin, 27 Serratia, 58 Ranke complex, 105 sex pilus, 9, 19 RANTES, 196 Shiga toxin, 58 reduviid bug, 247 Shigella, 58 relapsing fever, 98 shingles, 205 respiratory syncytial virus, 175 smallpox, 209 reticulate body, 79 specialized transduction, 18 retroviruses, 191 spectinomycin, 130 rev, 194 spirochetes, 5, 91 reverse transcriptase, 190 spores, 144 Reyes Syndrome, 174 S , 146 rhabdoviridae, 220 sporozoites, 242 rheumatic fever, 24 sprotrichosis, 146 rhinovirus, 217, 219 staphylococci, 31 ribavirin, 187, 216, 230, 233 S , 26 rickettsia, 83 S , 31, 32 R , 86 S , 36 R , 86 S , 36 R , 84 staphylokinase, 32 R , 87 stavudine, 202, 227, 231 R , 87 sterile pyuria, 106 rickettsialpox, 86 stibogluconate treatment, 250 rifampin, 134 streptococcal pharyngitis, 23 Rift Valley fever, 216 streptococcal toxic shock syndrome, 23, 24 rimantadine, 229, 232 streptococci, 22 risus sardonicus, 41 S , 27 ritonavir, 228, 232 S , 27 river blindness, 255 S , 27 RNA viruses, 161,166 S , 26 RNA-dependent RNA polymerase, 162 S , 26 R , 88 S , 26 R , 88 streptokinase, 23 Rocky Mountain spotted fever, 84 streptolysin O, 23 rotavirus, 219 streptolysin S, 23 roundworms, 251 streptomycin, 128, 135 RP59500, 27 S , 251 RPR tst, 93 subacute sclerosing panencephalitis, 178 RSV, 175 sulbactam, 117 rubivirus, 214 sulfatides, 102 rule of sixes, 93 superoxide dismutase, 6 saber shins, 93 suramin treatment, 250 saddle nose, 93, 109 Synercid, 27 Salmonella, 58 syphilis, 91 saquinavir, 202, 228, 232 T-cell death, 198 saprophytes, 144 T-strain Mycoplasma, 111 scalded skin syndrome, 32, 34 tabes dorsalis, 92 schistosomes, 256 Taenia Saginata, 259

280 INDEX

Taenia solium, 258 Tsutsugamushi fever, 87 tapeworms, 256 tuberculosis, 102 tat, 194 tuberculosis treatment, 133 tazobactam, 117 tularemia, 74 tellurite agar, 45 tumor necrosis factor, 12 tetanospasmin, 41 typanosoma cruzi, 242 tetany, 41 typhoid fever, 59 tetracycline, 128 typhus, 86 thalidomide, 136 Unasyn, 117 Thayer-Martin VCN media, 51 Ureaplasma urealyticum, 111 thiabendazole treatment, 253 ureidopenicillins, 117 thrush, 150 V virulence factor, 73 ticaricillin, 117 V3 loop, 201, 202 Timentin, 117 valacyclovir, 231 tinea capitis, 145 vancomycin, 140 tinea corporis, 145 vancomycin resistant enterococci, 27 tinea cruris, 145 varicella-zoster virus, 205 tinea nigra, 144 VDRL, 93 tinea pedis, 145 Vi antigen, 58 tinea unguium, 145 Vibrio cholera, 62 TNF, 12 Vibrio parahaemolyticus, 62 tobramycin, 128 vidarabine, 233 togaviridae, 214 viral load, 198 TORCH viruses, 205, 216 viral replication, 166 toxic shock syndrome toxin, 33 VRE, 27 toxins, 11 W virulence factor, 73 Toxoplasma gondii, 238 walking pneumonia, 111 tracheal cytotoxin, 70 warts, 210 trachoma, 80 wax D, 103 transduction, 16 Weils disease, 100 transformation, 16 Weil-Felix reaction, 84 transpeptidase, 114 West Nile virus, 216 transposons, 21 western blot test, 201 trematodes, 256 whipworm, 253 trench fever, 88 whooping cough, 70 Treponema pallidum, 91 wood tick 85 Treponema subspecies, 95 Woods light, 145 triazoles, 157 Wuchereria bancrofti, 255 Trichinella spiralis, 253 xenodiagnosis, 248 Trichomonas vaginalis, 236 yaws, 96 Trichuris trichiura, 253 yeast, 144 trifluridine, 233 yellow fever, 216 trimethoprim and sulfa, 141, 235 Y , 61 trismus, 41 Y , 73 trophozoite, 242 zalcitabine (ddC), 195, 202, 227, 231 tropical spastic paraparesis, 191 zanamavir, 229, 232 Trypanosoma, 245 ZDV, 194, 202, 225, 228, 231 trypanosomes, 241 zidovudine (ZDV), 194, 202, 225, 228, 231 trypomastigotes, 245 zoster, 205 tsetse fly, 241 Zosyn, 117

28 1