Microbiology

Bacteria Gram positive Gram negative Cocci  Staphylococcus (clusters and catalase +ve) Diplococci ↘Coagulase +ve (aureus) – skin, ,  Neisseria , formation ↘meningitidis – meningitis ↘Coagulase -ve (epidermidis; saprophyticus) ↘gonorrhoeae –gonorrhoea, , pharyngitis, disseminated CONS = Contaminants (unless foreign bodies present) infection, arthritis

 Streptococcus (strips and catalase -ve)  Moraxella ↘α-haemolytic i.e. partially lyse RBCs ↘catarrhalis –URTI s, chronic lung disease exacerbations, pneumonia -pneumoniae – pneumonia, meningitis, URTIs, invasive -viridans group (mitis, mutans, salivarius, sanguinis, anginosus) – endocarditis, dental ↘β-haemolytic i.e. completely lyse RBCs -Group A strep (pyogenes) – skin, Rh fever, scarlet fever, strep throat, post-strep GN, erysipelas, nectrotising fascitis, strep toxic shock -Group B strep (agalactiae) – vaginal colonisation, neonatal infection ↘Non-haemolytic -Group D strep (bovis; equinus) – bacteraemia -Enterococcus (faecium; faecalis) –UTIs, bacteraemia, endocarditis, diverticulitis Rods (bacilli) Big and spore forming Enteric Non-enteric  Clostridium (anaerobic) Long Coccobacilli ↘difficile – C diff diarrhoea  E. Coli  ↘tetani – tetanus – UTIs, gastroenteritis, ↘influenzae neonatal meningitis ↘perfringens – gas gangrene Aerobic glucose + – pneumonia, meningitis,  Klebsiella epiglottits ↘botulinum – botulism lactose fermenting – pneumonia, UTIs (COLIFORMS –  Bordetella  Enterobacter ↘pertussis  Bacillus normal bowel flora) – LRTIs, UTIs, skin, intra- – abdominal, endocarditis ↘anthracis – anthrax (infected animal/product spores →  Garnerella cutaneous: black ulcer, lymphadenopathy, fever;  Citrobacter ↘vaginalis lung: pneumonia; or GI: haematemsis/diarrhoea) – UTIs – vaginosis ↘cereus – gastroenteritis (improperly refrigerated rice)  Salmonella  – gastroenteritis, typhoid Acinetobacter – nosocomial infections Small and non-spore forming  Shigella  Legionella  Listeria – gastroenteritis/  Proteus Aerobic glucose ↘pneumophilia ↘monocytogenes – gastroenteritis, septicaemia, – Legionnaires’ disease

ENTEROBACTERIACEAE – UTIs, nosocomial only fermenting meningitis, encephalitis, pneumonia, neonatal, endocarditis (water tanks/air conditioners (risks = soft cheeses, unpasteurized milk, meats)  Yersinia → atypical pneumonia) – yersinosis (diarrhoeal  Coxiella  Corynebacterium illness),  Serratia ↘burnetii ↘diphtheriae – diphtheria, colonisation – (livestock → flu- – nosocomial like illness, pneumonia,  Pseudomonas Aerobic non- granulomatous hepatitis, – pneumonia, UTIs, sepsis, fermenting endocarditis) Gastrointestinal, wound  Brucella  Bacteroides Anaerobic – (unpasteurized – intra-abdominal milk → long flu-like illness) Curved  Pasteurella  Vibrio – pasturellosis (cat bite → septic phlegmon) ↘cholerae – (dysentery)  Francisella  Campylobacter (microaerophilic) – tularaemia (tick/deer fly ↘jejuni – gastroenteritis (raw meat) bite → ulcer at site of entry,  Helicobacter fever/sepsis, lymphadenopathy) ↘pylori – gastritis Spirochetes  Treponema ↘pallidum – syphilis  Borrelia ↘burgdorferi – Lyme disease  Leptospira – leptospirosis (spread by rodents) Branching  Actinomyces (anaerobic) filamentous – dental, actinomycosis () growth  Nocardia (partially acid fast) – pneumonia, endocarditis, encephalitis, brain abscess, skin Pleomorphic  Chlamydia ↘trachomatis – cervicitis/urethritis ↘psittaci – psittacosis/pneumonia (spread by birds)  Rickettsiae – , , , , Rocky Mountain (all tick borne) Unique cell  Mycobacterium (acid fast) wall ↘tuberculosis – TB No cell wall  Mycoplasma ↘pneumoniae – pneumonia

© 2013 Dr Christopher Mansbridge at www.OSCEstop.com, a source of free OSCE exam notes for medical students’ finals OSCE revision . Antibiotics Gram Positive Gram Negative

Cocci Rods (bacilli) Class Subclass Antibiotic Enterococcus MRSA Staphylococcus Streptococcus Neisseria Haemophilus E. Coli and Β-lactamase Pseudomonas Anaerobes Atypical aureus (MSSA) meningitidis coliforms resistance* (except C. Diff) β-lactams Flucloxacillin β-lactam ring Large so not affected by ++++ + lodges in β-lactamase

bacterial cell Benzylpenicillin Staph secretes -Penicillinase wall penicillinase ++++ ++ -ESBL + Amoxicillin/ (β-lactamase that -Amp C destroys β-lactam - Carbapenemase ring of ) +++ + + Many resistant Co-Amoxiclav -Amp C (Amoxicillin + β- (resistant to inhibitor) MRSA is ++ -Carbapenemase lactamase inhibitor) ++ resistant to Tazocin (Piperacillin + β-lactams due ESBLs sensitive in vitro Not all β-lactamase inhibitor) to modification +++ but have variable +++ ++ of penicillin activity in vivo Carbapenems Meropenem binding protein -Carbapenemase

Antibiotic of choice for +++ ESBL/Amp C Target cell wall nd +++ 2 gen Cefuroxime Cefuroxime doesn’t -ESBL (but sensitive to penetrate BBB cephamycins)

3rd gen / ++ -Amp C Ceftazidime is used Cephalosporins Cefotaxime ++++ -Carbapenemase for pseudomonas only (best agent) 4th gen Cefepime -ESBL (variable) Cephalosporins -Carbapenemase +++ (variable) +++ Glycopeptides Vancomycin/ Inhibit peptidoglycan links in cell wall Teicoplanin +++ +++ ++ + Some strains resistant (VRE)

Aminoglycosides Some cross resistance Inhibit 30S ribosomal subunit + + +++ with ESBL and +++ use oxygen carbapenemase dependent active transport Tetracyclines Doxycycline Inhibit 30S ribosomal subunit ++ +/- ++ Lincosamides Clindamycin ++ Inhibit 50S ribosomal subunit ++ ++ ++

protein synthesis Macrolides Erythromycin/ ++ Inhibit 50S ribosomal subunit Clarithromycin/ ++ +++ Azithromycin (gram -ve)

Target Misc Chloramphenicol Inhibit 50S ribosomal subunit ++ + + + + + +/- ++

Fluroquinolones Ciprofloxacin Some cross resistance Inhibit DNA gyrase + +++ +++ with ESBL and ++ +++ carbapenemase Not alone

Misc Metronidazole Inhibit DNA +++

DNA Trimethoprim + ++

Co-trimoxazole Some cross resistance Target + (sulfamethoxazole + ++ ++ with ESBL and trimethoprim) carbapenemase Nitrofurantion ++ ++ Atypical pneumonias: legionella (gram –ve), mycoplasma Coliforms (lactose-fermenting ): E. Coli, enterbacter, klebsiella Anaerobes: clostridium (gram +ve rod), bacteroides (gram -ve rod) Other important bacteria to know antibiotics for: mycobacterium (gram +ve rod); clostridium difficile (gram +ve rod); chlamydia (gram –ve) *β-lactamase resistance: β-lactamases are enzymes produced some bacteria which break down the β-lactam ring of certain β-lactam antibiotics and cause resistance. Penicillinase is produced by several bacteria, most notably staphylococcus; the other β-lactamases (ESBL, Amp C, carbapenemase) are mainly produced by some enterobacteriaceae. © 2013 Dr Christopher Mansbridge at www.OSCEstop.com, a source of free OSCE exam notes for medical students’ finals OSCE revision . Coverage Needed Gastroenteritis/diarrhoea → ceftriaxone/ciprofloxacin/azithromycin Community acquired pneumonia  Salmonella enteritidis  Streptococcus pneumoniae  Shigella  Haemophilus influenza (if not vaccinated)  Campylobacter  Atypicals  E. coli (enterotoxic)

If immunocompromised (i.e. malnourished, alcoholic, diabetic, on long term steroids), also: staphylococcus aureus, coliforms, TB Less common: , bacillus cereus, staphylococcus aureus If severely immunosuppressed (i.e. HIV with CD4<200, transplant recipient): pneumocystis carinii, cryptococcus, CMV, varicella zoster virus, influenza, fungal If been at risk, also: clostridium difficile, , salmonella typhi infections If dysentery: shigella, vibrio cholera, amoeba Don’t forget viral, parasitic and non-infectious causes! Hospital acquired pneumonia  Staphylococcus aureus (including MRSA) Skin/joints/bone  Anaerobes  Staphylococcus aureus  Coliforms  Streptococcus pyogenes

 Pseudomonas For wound/ulcer infections or severe/necrotising cellulitis, also: anaerobes For burns, also: anaerobes, pseudomonas For post-surgical wounds, also: gram negative bacilli (e.g. E. coli, kelbsiella, pseudomonas), enterococci, MRSA, CONS Colonising bacteria in chronic respiratory ill health (may or may not cause infection e.g. exacerbation) NB. wound colonising bacteria (colonise exudate without necessarily causing infection) include: coliforms, enterococcus, anaerobes  Streptococcus pneumoniae  Meningitis   Nisseria meningitidis (meningococcal)  Staphylococcus aureus  Streptococcus pneumonia (pneumococcal)  Pseudomonas  Haemophilus influenza (if not vaccinated)  Listeria (if >65y or immunocompromised) In cystic fibrosis, also: burkholderia cepacia If neonatal: group B streptococcus, E. coli/coliforms, listeria (rare) Upper respiratory tract infections  Streptococcus pneumoniae Urine  Streptococcus pyogenes 1. E. coli  Haemophilus influenzae 2. Staphylococcus saprophyticus  Moraxella catarrhalis 3. Non-E. Coli enterobacteriaceae (klebsiella, enterobacter, proteus), pseudomonas, enterococci, staphylococci (CONS/aureus)

Cavitating pneumonia Less common organisms (3) are associated with: catheters, hospital, structural abnormalities and instrumentation  Streptococcus pneumoniae  Staphylococcus aureus  Klebsiella  Viridans group streptococci and other streptococci (e.g. bovis)  TB  Enterococci  Anaerobes  Staphylococcus aureus and coagulase negative staphylococci (e.g. epidermidis)  Intra-abdominal (including biliary)  HACEK organisms Normal bowel flora:  Anaerobes e.g. bacteroides Surgical prophylaxis  Coliforms  Need to cover skin ± intra-abdominal  Enterococcus Sepsis of unknown origin  Need to cover skin, chest, urine, meningitis, intra-abdominal © 2013 Dr Christopher Mansbridge at www.OSCEstop.com, a source of free OSCE exam notes for medical students’ finals OSCE revision .