2017/2018
Microbiology Phase 2a Wrap-up Session Krishanth Ganesan 24/1/19 The Peer Teaching Society is not liable for false or misleading information…
Microbiology Objectives Cover things you actually need to know Various tests for each organism Approach to antibiotics Resources The Peer Teaching Society is not liable for false or misleading information…
How to study Study microbiology by condition, not the organism Eg study infective endocarditis and its associated organisms, not staph aureus, strep pyogenes etc The things that they might test you with regards to organisms is recognising them on microscope (described in text eg gram –ve diplococci) or tests to identify a certain bug (+ve optochin test) The Peer Teaching Society is not liable for false or misleading information…
Approach to bacteria Determine if it is: Gram +ve or –ve Cocci, bacilli or others In clusters or chains The Peer Teaching Society is not liable for false or misleading information…
Bacteria - shapes Cocci Bacilli Spirochaete – eg Treponema pallidum (syphilis), borrelia burgdorferi (Lyme disease) The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram +ve or -ve Gram +ve: Purple Contains peptidoglycan that is stained by crystal violet Gram –ve: pink Has a lot less peptidoglycan that is not stained, by instead stained by safranin The Peer Teaching Society is not liable for false or misleading information…
Bacteria – staph vs strep Staph in clusters Strep in chains The Peer Teaching Society is not liable for false or misleading information…
Bacteria – Gram +ve cocci in clusters Catalase test: H2O2 + Staphylococci → Gas bubbles +ve = staph -ve = non staph The Peer Teaching Society is not liable for false or misleading information…
Bacteria – Gram +ve cocci in clusters Now that you know it’s a staph.. Is it staph aureus? Coagulase test +ve = staph aureus since it produces coagulase that converts fibrinogen to fibrin -ve = coagulase –ve staph The Peer Teaching Society is not liable for false or misleading information…
Bacteria – Gram +ve cocci in clusters Eg of coag –ve staph = staph epidermis The Peer Teaching Society is not liable for false or misleading information…
Bacteria – Gram +ve cocci in chains The Peer Teaching Society is not liable for false or misleading information…
Bacteria – Gram +ve cocci in chains Blood agar can undergo 3 types of haemolysis depending on the organism Beta haemolysis: complete Alpha: partial Gamma: none The Peer Teaching Society is not liable for false or misleading information…
Bacteria – alpha haemolytic strep Alpha haemolytic strep – only 2 important bugs, you want to know if it is strep pneumoniae If optochin +ve = strep pneumoniae (clear demarcated ring around optochin disc) Optochin resistant = strep viridians Strep pneumo on microscopy = Gram +ve diplococci The Peer Teaching Society is not liable for false or misleading information…
Bacteria – beta haemolytic strep Lancefield test – groups bacteria based on carbohydrate composition of bacterial antigen on cell wall, normally for beta-haemolytic strep A: Streptococcus pyogenes B: Streptococcus agalactiae D: Enterococcus, Strep bovis (group D is not beta- haemolytic) The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram +ve bacilli Gram +ve bacilli that are important Listeria monocytogenes Propionibacterium acne – acne Clostridium difficile – diarrhoea from antibiotic overuse (those starting with C) The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram –ve bacilli MacConkey agar: Contains bile salts, lactose & neutral red (pH indicator) Identifies bacteria that can ferment lactose (normally gram-ve enteric bugs) Ferment lactose -> produce acid -> pH drop <6.8= pink, or if pH>6.8, remains normal colour The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram –ve bacilli Yellow - non fermenters - salmonella, shigella, pseudomonas aeruoginosa, proteus mirabilis Pink - fermenters - e.coli, klebisella pneumoniae The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram –ve bacilli The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram –ve bacilli Done macconkey, it’s yellow: Perform oxidase test: Black/purple = +ve = pseudomonas or Neisseria(note it is cocci not bacilli) Additional anti-pseudomonal sensitivity tests required to identify pseudomonas Colourless = -ve = shigella, salmonella, proteus The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram –ve bacilli Proteus mirabilis: Swarms on many agars, difficult to identify other bacteria growing (normally urinary tract) CLED is used to inhibit proteus To identify proteus: urease test +ve The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram -ve cocci Neisseria meningitidis, gonorrhoea Moraxella catarrhalis Any Neisseria on microscopy: gram –ve diplococci The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram -ve other rods Comma/curved shaped: Vibrio cholera – rice water stool Helical shape: Campylobacter jejuni – bloody diarrhoea Helicobacter pylori – gastric and duodenal ulcer Coccobacilli: Haemophilus influenza The Peer Teaching Society is not liable for false or misleading information…
Bacteria – gram -ve other shapes Haemophilus influenza Gram –ve coccobacilli, requires factor X and V to grow Fastidious bacteria: requires chocolate agar which is blood agar but with lysed RBCs due to heating to 80 deg C (haem from factor X) Neisseria meningitidis also requires chocolate agar The Peer Teaching Society is not liable for false or misleading information…
Mycobacteria Most important = m. tuberculosis Can get bovine TB from m. bovis from cows The Peer Teaching Society is not liable for false or misleading information…
Mycobacteria Takes long to culture, have to be cultured with Löwenstein–Jensen medium mycolic acid in the cell wall does not absorb normal gram-staining: requires Ziehl-Neelsen stain to identify acid-fast bacilli The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Learn mechanism of antibiotics Much better to learn the empirical antibiotics used for each condition than trying to learn specific antibiotics for certain bugs Eg CURB65 - pneumonia Empirical antibiotics may differ from trust to trust when you start working Learn side effects of TB drugs The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Some bugs have definite antibiotics, such as: Vancomycin for MRSA Metronidazole for entamoeba histolytica, giardia Co-trimoxazole for PCP CURB65 score for pneumonia and their respective antibiotic regimens Vancomycin/metronidazole for C. difficile The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Important side effects: Folate antagonist eg trimethoprim and pregnancy Aminoglycoside such as gentamicin – ototoxicity, renal impairment C drugs for C.diff Carbapenems Ciprofloxacin (Quinolones) Co-amoxiclav (Penicillins) Cephalosporins (especially 2nd and 3rd generation) Clindamycin The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Learn mechanism of antibiotics Much better to learn the empirical antibiotics used for each condition than trying to learn specific antibiotics for certain bugs Empirical antibiotics may differ from trust to trust when you start working Some bugs have definite antibiotics, such as: Vancomycin for MRSA Metronidazole for entamoeba histolytica, giardia Co-trimoxazole for PCP The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Learn mechanism of antibiotics Much better to learn the empirical antibiotics used for each condition than trying to learn specific antibiotics for certain bugs Empirical antibiotics may differ from trust to trust when you start working Some bugs have definite antibiotics, such as: Vancomycin for MRSA Metronidazole for entamoeba histolytica, giardia Co-trimoxazole for PCP The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics Learn mechanism of antibiotics Much better to learn the empirical antibiotics used for each condition than trying to learn specific antibiotics for certain bugs Empirical antibiotics may differ from trust to trust when you start working Some bugs have definite antibiotics, such as: Vancomycin for MRSA Metronidazole for entamoeba histolytica, giardia Co-trimoxazole for PCP The Peer Teaching Society is not liable for false or misleading information…
Approach to antibiotics The Peer Teaching Society is not liable for false or misleading information…
Virus PCR normally if needed Infectious mononucleosis/glandular fever-like sx: Epstein-barr, cytomegalovirus, toxoplasmosis gondii (parasite), deadly in immunocompromised individuals HIV Upper respiratory tract infections Deadly bugs: smallpox etc (learn more in 3a, paediatric bugs) The Peer Teaching Society is not liable for false or misleading information…
Fungi Normally in immunocompromised individuals Candida albicans – treat with antifungal eg topical nystatin, oral fluconazole Pneumocystis pneumonia – treat with co-trimoxazole Aspergilliosis – CF, bronchiectasis patients The Peer Teaching Society is not liable for false or misleading information…
Helminths Very rare, need to know these at most: Wucheria bancroftii – filariasis causing lymphoedema Enterobius vermicularis – common in uk, itchy bum, spreads in household Schistosomiasis – causes squamous cell bladder cancer Hookworm - Worldwide cause of iron-deficiency anaemia Treatment: normally mebendazole The Peer Teaching Society is not liable for false or misleading information…
Protozoa Entamoeba histolytica: bloody diarrhoea, liver abscess Treat with metronidazole Malaria: learn in haematology, 5 types, plasmodium falciparum most important Giardia: diarrhoea due to alteration of intestinal villi, reducing absorption The Peer Teaching Society is not liable for false or misleading information…
Quiz What is the role of catalase test? A: identifies staph aureus B: identifies staph from non-staph C: identifies mycobacterium D: identifies fungi The Peer Teaching Society is not liable for false or misleading information…
Quiz What is the role of catalase test? A: identifies staph aureus B: identifies staph from non-staph C: identifies mycobacterium D: identifies fungi The Peer Teaching Society is not liable for false or misleading information…
Quiz What is the role of coagulase test? A: identifies staph aureus B: identifies staph from non-staph C: identifies mycobacterium D: identifies fungi The Peer Teaching Society is not liable for false or misleading information…
Quiz What is the role of coagulase test? A: identifies staph aureus B: identifies staph from non-staph C: identifies mycobacterium D: identifies fungi The Peer Teaching Society is not liable for false or misleading information…
Quiz For which group of bacteria should you do an optochin test? A: alpha-haemolytic staph B: alpha-haemolytic strep C: beta-haemolytic strep D: enterococcus The Peer Teaching Society is not liable for false or misleading information…
Quiz For which group of bacteria should you do an optochin test? A: alpha-haemolytic staph B: alpha-haemolytic strep C: beta-haemolytic strep D: enterococcus The Peer Teaching Society is not liable for false or misleading information…
Quiz Optochin +ve test: what is the bug? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Optochin +ve test: what is the bug? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Example of group A strep? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Example of group A strep? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Example of group B strep? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Example of group B strep? A: strep pneumoniae B: strep viridians C: strep pyogenes D: strep agalactiae The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following describes C. difficile? A: gram –ve bacilli B: gram –ve cocci C: gram +ve cocci D: gram +ve bacilli The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following describes C. difficile? A: gram –ve bacilli B: gram –ve cocci C: gram +ve cocci D: gram +ve bacilli The Peer Teaching Society is not liable for false or misleading information…
Quiz Antibiotic for C. difficile A: amoxicillin B: cefotaxime C: carbapenem D: metronidazole The Peer Teaching Society is not liable for false or misleading information…
Quiz Antibiotic for C. difficile A: amoxicillin B: cefotaxime C: carbapenem D: metronidazole The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following is gram +ve diplococci on microscopy A: Neisseria gonorrhoea B: strep pneumoniae C: Moraxella catarrhalis D: mycobacterium tb The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following is gram +ve diplococci on microscopy A: Neisseria gonorrhoea B: strep pneumoniae C: Moraxella catarrhalis D: mycobacterium tb The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following is gram -ve diplococci on microscopy A: Neisseria gonorrhoea B: strep pneumoniae C: Moraxella catarrhalis D: mycobacterium tb The Peer Teaching Society is not liable for false or misleading information…
Quiz Which of the following is gram -ve diplococci on microscopy A: Neisseria gonorrhoea B: strep pneumoniae C: Moraxella catarrhalis D: mycobacterium tb The Peer Teaching Society is not liable for false or misleading information…
Quiz When is chocolate agar important? To culture: A: mycobacterium tb B: haemophilus influenza C: Treponema pallidum D: Not important, blood agar can be substituted The Peer Teaching Society is not liable for false or misleading information…
Quiz When is chocolate agar important? To culture: A: mycobacterium tb B: haemophilus influenza C: Treponema pallidum D: Not important, blood agar can be substituted The Peer Teaching Society is not liable for false or misleading information…
Quiz MacConkey test – shows yellow, what possible bug? A: pseudomonas aeruginosa B: e.coli C: klebsiella pneumoniae The Peer Teaching Society is not liable for false or misleading information…
Quiz MacConkey test – shows yellow, what possible bug? A: pseudomonas aeruginosa B: e.coli C: klebsiella pneumoniae The Peer Teaching Society is not liable for false or misleading information…
Quiz MacConkey test – shows pink, what bug? A: pseudomonas aeruginosa B: staph aureus C: strep pneumoniae D: e.coli The Peer Teaching Society is not liable for false or misleading information…
Quiz MacConkey test – shows pink, what bug? A: pseudomonas aeruginosa B: staph aureus C: strep pneumoniae D: e.coli The Peer Teaching Society is not liable for false or misleading information…
Quiz Which stain is needed for mycobacteria? A: Lowenstein-Jensen stain B: Methylene blue C: Oxidase purple D: Ziehl-Neelsen stain The Peer Teaching Society is not liable for false or misleading information…
Quiz Which stain is needed for mycobacteria? A: Lowenstein-Jensen stain B: Methylene blue C: Oxidase purple D: Ziehl-Neelsen stain The Peer Teaching Society is not liable for false or misleading information…