هذا العمل ل يغني عن الرجع الساسي للمذاكرة Lecture 9 Anaerobic Bacteria • Important • Term • Extra explanaon • Addi7onal notes Objectives • Describe anaerobic bacteria including their sensitivity to oxygen and where they may be found in the environment and the human body. • Differentiate the various types of anaerobes with regard to atmospheric requirement (i.e. obligate anaerobes, Faculative anaerobes and aerotolerent anaerobes. • Describe how anaerobes, as part of endogenous microbiota, initiate and establish infection. • Name the endogenous anaerobes commonly involved in human infection. • Recognize specimens that are acceptable and unacceptable for anaerobic culture. • Give the clues(sign and manifestations) to anaerobic infection, name the most probable etiologic agents of the following(Wound botulism, gas gangrene, tetanus, Actinomycosis, Pseudomembranous colitis and bacterial vaginosis) • Describe the microscopic and colony morphology and the results of differentiating anaerobic isolates. • Discuss antimicrobial susceptibility testing of anaerobes including methods and antimicrobial agents to be tested. • Describe the major approaches to treat anaerobic-associated diseases either medical or surgical. Need oxygen Are poisoned Need oxygen because they An organism that because they cannot by oxygen, so cannot ferment or respire makes ATP by ferment or respire they gather at anaerobically. However, aerobic respiration if anaerobically. They the bottom of they are poisoned by high oxygen is present, gather at the top of the tube concentrations of oxygen. but is capable of the tube where the where the They gather in the upper switching to oxygen oxygen part of the test tube but fermentation or concentration is concentration not the very top. anaerobic respiration highest. is lowest. if oxygen is absent. Why can’t anaerobic bacteria survive in oxygen? The presence of oxygen leads to the production in cells of the superoxide radical (a negatively charged O2 molecule). Normally, the superoxide anion is lethal enough to kill almost any organism. Aerobic organisms and facultative anaerobes have the enzymes superoxide dismutase and catalase. These enzymes work together to convert superoxide to oxygen and hydrogen peroxide. * Lack cytochrome-cannot use oxygen as hydrogen acceptor * Most Lack Catalase & Peroxidase Anaerobiosis * Contain flavoprotein so in the presence of oxygen produce H2O2 which is toxic * Some lack enzyme superoxide dismutase so many killed , peroxide and toxic radicles * enzyme like fumarate reductase must be in reduced form to work Habitat: Normal Flora in… Oropharynx Gastrointestinal tract Female genital tract • Provetella melaninogenicus • Found mainly in the large colon in large numbers • Mainly in the • Total number of anaerobes = 10 • Fusobacteria 11 vagina • • While all aerobes (including E. coli) = 10 14 • examples are (1) B acteroides +Skin, Nose, • Veillonella fragilis (2) Bifidobacterium Endocervix and species Urethra § Pathophysiologic states § Antimicrobial agents, H-Blockers, antacids MODIFIED BY § Hormonal changes § Age Classification A. NON SPORE FORMINGN B.SPORE FORMING {MORE COMMON} GRAM POSITIVE BACILLI GRAM NEGATIVE BACILLI GRAM POSITIVE BACILLI (cocco bacilli) Actinomyces Clostridia Bacteroides • Propionobacterium • Bacteroides fragilis • CL .perfringens propionicum (resistant to penicillin) • Dominate the CL .Septicum o • p.acne • Prevotella spp indigenous flora • Bifidobacterium • Leptotricha buccalis • CL .novyi (colonization • LAEuobacterium • fusobacterium spp • CL .Histolyticum resistance) Commonly found • CTOBACILLUS (The main cause of pharyngitis ) o • CL .Difficile in infection • Actinomyces israelii f.nucleatum o Easy to overlook • CL .Tetani - Special precautions- • CL .Botulinum - Slow growth GRAM POSITIVE COCCI GRAM NEGATIVE COCCi Importance - Mixed infection o Difficult treatment • Peptococci • Viellonella sp. (diplococci) (staphylococcus) • Peptostreptococci (streptococci) • Account for 1/3 of all isolates Bacteroides species other * Flagyl (metronidazole) Bacteroides: • Resistant to 20% bile is the drug of choice. 1.B. Fragilis Group than B. Fragilis group Clindamycin can also • Bile sensitive • Resistant to many antibiotics~* be used. 2.B.Vulgaris • Resistant to kanamycin only Penicillin, kanamycin, vancomycin, colistin…etc 3.B.Thetaiotamicron • Some pigmented • No pigmentation of colonies or fluorescence 4. B.Uniformis Features of anaerobic infections Infections are always near to the site of the body which are habitat. *Infection from animal bites. ( ُخراج) .Deep abscesses * * The infections are also polymicrobial (caused by several types of microorganisms) * Gas formation, foul smell * Detection of "Sulphur granules"' due to Actinomycosis * Failure to grow organism from pus if not culture anaerobically. * Failure to respond to usual antibiotics. * Suppuration * Tissue destruction{gangrene} * Septic thrombophlebitis • Some have unique pathology: (Actinomycosis, Psedomembranous colitis, Gas Sulphur granules gangrene) One of the small yellow bodies found in the pus of actinomycotic What are the infection caused by these anaerobic organisms ? abscesses and consisting * Post operative wound infection of clumps of the * Brain abscess causative actinomycete * Dental abscesses * Lung abscess * Intra-abdominal abscess, appendicitis, diverculitis * All these infection can cause bacteremia * Infection of the female genital tract * Septic abortion * Puerperal infection or sepsis * Endometritis * Pelvic abscess or other abscess * Other infections a) Breast abscess in puerperal sepsis b) Infection of diabetic patients (diabetic foot infections). c) Infection of pilonidal sinus EPIDEMIOLOGY Almost all infections are indigenous except ( الكزاز - تشنج العضلت) Tetanus* (تسمم من أكل اللحوم) Infant ,wound botulism* * Gas gangrene { some cases } * Bites * C .difficile {nosocomial (acquired or occurring in a hospital) } PREDISPOSING FACTORS: • Trauma • Low O tension {Eh} • Cholecystitis • Trauma, dead tissue , deep wound • Obstruction • Impaired blood supply • Ulceration • Presence of other organisms • Diabetes mellitus • Foreign bodies • Pylephlebitis • Antibiotic therapy • Diverticula formation • Neoplasm How does Infections begin? Laboratory diagnosis: Disruption of barriers When anaerobic infection is v Trauma suspected; v Operations a) Specimens have to be collected from v Cancerous invasion of tissues the site containing necrotic tissue. Disruption of blood supply b) Pus is better than swabs. v Drops oxygen content of tissue c) Specimens has to be send to the v Decrease in Eh potential laboratory within 1/2 hour. (redox potential) d) Fluid media like cooked meat broth v Tissue necrosis are the best culture media. e) Specimens have to incubated anaerobically for 48 hours. ACTINOMYCOSIS Actinomyces are branching anaerobic or microaerophilic Gram positive bacilli. Source of the infection: normal flora and the host An intrauterine device (IUD or coil) is a usually normal host. small contraceptive device, often 'T'-shaped, often containing either copper or levonorgestrel, which is inserted into the uterus. They are one Primary site of the infection: mouth, lung, form of long-acting reversible contraception appendix, uterus with IUD* (chronic infection) which are the most effective types of reversible birth control. Infection can spread to: brain, liver, bone and blood. • Diagnosis: by Gram stain with sulfur granules and growth of molar tooth colonies. • Treatment: penicillin, clindamycin or tetracycline. Clostridium perfringens (CI . welchii) Cl. tetani (TETANUS) Morphology • Morphology gram +ve anaerobic with terminal spore Drum Stick large rods gram +ve with bulging endospores. appearance Laboratory diagnosis • Lives in soil and animal feaces. e,g horse and any wound can * Smear Gram stain Large Gram positive bacilli with few infected if contaminated by spores • Face & neck wounds are more dangerous or no WBCs. Clinical Features * Culture Incubation period 1-2 weeks (time from infection to the appearance of - Blood agar with haemolytic colonies (double symptoms) zone of haemolysis Symptoms: - Cooked meat medium Painful muscle spasm around infected wound and Contraction of * Gives the NAGLAR'S Reaction & toxin neutralization on muscles in the face called Trismus (Lockjaw) , Risus Sardonicus - Egg yolk medium & toxin is a phospholipase strychnine or back called araching of Back • Opisthotonus in children. Opistho meaning "behind" and tonos Can leads to the following diseases meaning "tension",due to extrapyramidal effect and is caused - Wound Contamination by spasm of the axial along the spinal column . - Wound infection Pathogenesis - Gas Gangrene - most important disease Mainly due to tetanospasmin which is powerful exotoxin - Gas Gangrene of the uterus in criminal abortion (protein) .This organism does not lead to invasion or Bacteraemia . Its - Food Poisoning : Spores are swallowed à Germinate in function to inhibit transmission of normal inhibitory messages from gut after 18 hours(Toxin production) à abdominal pain central nervous system at anterior horn cells of cord. and diarrhoea Pathogenesis Diagnosis Traumatic open wounds or compound fractures lead to Mainly by clinical and it is strict anaerobe very motile , spread on muscle damages and contamination with dirt etc, agar. v Mainly in war wounds, old age, low blood supply and amputation of thigh (required prophylaxis with Prevention penicillin) By vaccination Treatment Prevention and Treatment Cleaning of wound and removal of Foreign