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Microbiology Revision

Microbiology Revision. Dr Anna Goyder and Dr Helen McKenna 19/03/13 - 21/03/13. Outline. 2 lectures x 90mins each: Bacteria and Abx Viruses and Antivirals Vaccinations Infections by system: - CNS - Cardio - Resp - GI/hepatitis - GU/gynae - Musculoskeletal Mycobacterial

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Microbiology Revision

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  1. Microbiology Revision Dr Anna Goyder and Dr Helen McKenna 19/03/13 - 21/03/13

  2. Outline 2 lectures x 90mins each: Bacteria and Abx Viruses and Antivirals Vaccinations Infections by system: - CNS - Cardio - Resp - GI/hepatitis - GU/gynae - Musculoskeletal Mycobacterial Zoonoses Protozoa

  3. Recap

  4. Bacteria simplified Gram positive Cocci staphylococcus streptococcus enterococcus Rods/bacilli ABCDL (see next slide) Gram negative Cocci the diplococci - neisseria (gonorrhoea, meningitidis ‘meningococcus’), moraxella Rods/bacilli ENTERICS - E Coli, salmonella, shigella, klebsiella, proteus, campylobacter, helicobacter, vibrio… ie most other things! Coccobacillihaemophilus, legionella, brucellosis, bordetella, chlamydia* rickettsia* *obligate intracellular Spiral spirochetes – treponema (syphilis), leptospira (Weil’s), borrelia (lyme)

  5. Gram + rods:ABCDL Actinomyces Bacillus (anthracis, cereus) Clostridium (difficile, botulinum, perfringens) Diphtheria (corynebacterium diphtheriae) Listeria

  6. Respiratory Tract Infections

  7. Lower Respiratory Tract Infections • Acute bronchitis: Medium airways Irritating cough/sputum Tightness, wheeze Mild fever Scattered crackles Normal CXR CAUSES: Viral with secondary bacterial infection in smokers/COPD (pneumococcus, Hib, Moraxella) Treatment: Bronchodilators, respiratory physiotherapy to mobilise secretions. 2. Pneumonia Alveoli Productive cough SICKER: fever, pleuritic pain Localised signs of consolidation (dull to percussion, crackles, bronchial breathing) CXR: lobar, bronchopneumonia ASSESS SEVERITY : CURB 65 C onfusion (AMTS <8) U rea >7 RR >30 BP < 90/60 >65 years old 0-1: outpatient 2: admit 3-5: consider HDU/ITU

  8. Community Acquired Pneumonia

  9. Which organism is responsible? 65 year old man presents to A&E Productive cough and pleuritic chest pain Rusty sputum: Gram positive cocci 30 year old pregnant woman presents to GP Recent flu-like symptoms for last week Now has productive cough and fever

  10. Hospital Acquired Pneumonia Inpatient > 48 h: • Staph aureus (including MRSA) • Aerobic Gram negative rods (Coliforms, Enterobacter, Pseudomonas) 3. Aspiration: Anaerobes (most likely RLL) 4. Fungi Now need to cover gram negative rods, including pseudomonas (and, if suspect aspiration – anaerobes) 1. Ciprofloxacin (or tazocin) 2. MRSA -> ADD vancomycin 3. VRSA -> ADD linezolid

  11. Pseudomonas Naturally resistant to a large range of antibiotics Develops resistance after unsuccessful treatment (porin modification) Anti-pseudomonals include: Aminoglycosides (gentamicin/amikacin) Quinolones (ciprofloxacin) Cephalosporins (ceftazidime – not ceftriaxone) Certain Penicillins (piperacillin) Carbapenems (Meropenem) Polymixin B and colistin All must be given intravenously – apart from ciprofloxacin

  12. Questions 40 year old woman admitted with pneumonia following holiday in Turkey. Bloods show hyponatraemia and deranged liver function. Which investigation is most likely to confirm the diagnosis? A Sputum culture B Urinary Ag C Blood culture D Bone marrow aspirate E LP

  13. 28 year old man admitted with SOB and fever. 2/7 itchy vesicular rash after contact with brother with chicken pox. T 39, HR120, BP 135/68, Sats 95% OA Chest: occasional fine crackles Which is the most important intervention? A Elective intubation within next 24h B Prednisolone C VZIg D IV aciclovir E Paracetamol

  14. 17 year old presents with 4/7 sore throat, headache and lethargy. Doctor prescribed course of amoxicillin for URTI. 2/7 later her symptoms persist and she develops a maculopapular rash. A Kawasaki Disease B Penicillin allergy C HIV seroconversion D Beta-lactamase producing streptococcal infection E Infectious mononucleosis

  15. Gastro/Hepatology • Diarrhoea and vomiting • Hepatitis

  16. Bacteria simplified Gram positive Cocci staphylococcus streptococcus enterococcus Rods/bacilli ABCDL – Bacillus, Clostridium, Listeria Gram negative Cocci the diplococci - neisseria (gonorrhoea, meningitidis ‘meningococcus’), moraxella Rods/bacilli ENTERICS - E Coli, salmonella, shigella, klebsiella, proteus, campylobacter, helicobacter, vibrio… ie most other things! Coccobacillihaemophilus, legionella, brucellosis, bordetella, chlamydia* rickettsia* *obligate intracellular Spiral spirochetes – treponema (syphilis), leptospira (Weil’s), borrelia (lyme)

  17. Gastro – D&V Incubation period 1-6 hrs: Staphylococcus aureus, Bacillus cereus* 12-48 hrs: Salmonella, Escherichia coli 48-72 hrs: Shigella, Campylobacter > 7 days: Giardiasis, Amoebiasis *vomiting subtype, the diarrhoeal illness has an incubation period of 6-14 hours – note shorter incubation time for vomiting bugs www.passmedicine.com

  18. Bacterial gastroenteritis

  19. Gastro - Salmonella Gram negative rods Not normally present as commensals in the human GI tract.  S. Enteritidis infection occurs following contamination with animal faeces

  20. C. Inhibitors of DNA synthesis Quinolones – Ciprofloxacin, Moxifloxacin, Levofloxacin(thinkCiprofloxaquin, Moxifloxaquin etc) Act on DNAGyrase Active mostly against Gram negatives – use for UTIs, bacterial gastroenteritis Recap:

  21. Bacterial gastroenteritis

  22. Gastro – E. Coli Most strains are harmless, flora Classified by virulence factors and diseases caused: • ETEC – enteroToxigenic, Traveller’s diarrhoea - produces two exotoxins, similar to cholera – heat labile toxin (LT) and heat stable toxin (ST) – watery osmotic diarrhoea, non-invasive, no fever • EPEC – enteroPathogenic, moderately invasive. Similar to shigella – Shiga toxin/verotoxin • EIEC – enteroInvasive – dysentery – causes host response - clinically identical to Shigella • EHEC – enteroHaemorrhagic – e.g. infamous O157:H7 strain – shiga toxin, inflammatory response, can cause Haemolytic Uraemic Syndrome

  23. Bacterial gastroenteritis

  24. C. difficile - SBA A 88-year-old patient develops profuse, offensive watery diarrhoea following a course of co-amoxiclav. Clostridium difficile diarrhoea is diagnosed. On examination, her observations are stable, she is apyrexial and has no abdominal signs. What is the most appropriate first-line therapy?A.Oral vancomycin B.Oral metronidazole C.Oral metronidazole + vancomycin D.Faecal transplant E.Probiotic yoghurt

  25. Gastro – Clostridium difficile Gram positive rod

  26. Gram positive rods:ABCDL Actinomyces Bacillus (anthracis, cereus) Clostridium (difficile, botulinum, perfringens) Diphtheria (corynebacterium diphtheriae) Listeria Recap:

  27. Gastro – Clostridium difficile Gram positive rod Exotoxin produced-> damages gut -> pseudomembranous colitis. Features Diarrhoea, abdominal pain a raised white blood cell count is characteristic if severe toxic megacolon may develop Hospital acquired infection (HAI) EPIDEMIC Associated with loss of normal gut flora – commonly after broad-spectrum antibiotics.

  28. Gastro – Clostridium difficile Diagnosis Clostridium difficile toxin (CDT) in the stool Management first-line therapy is oral metronidazole for 10-14 days if severe or not responding to metronidazole then oral vancomycin may be used for life-threatening infections a combination of oral vancomycin and intravenous metronidazole should be used

  29. Anaerobes OBLIGATE CANNOT use O2/grow where there is oxygen Bacteroides Clostridium Actinomyces Recap: • FACULATIVE • Can grow where there is OR isn’t oxygen • Staphylococcus, E. Coli, Listeria

  30. C. Inhibitors of DNA synthesis Quinolones – Ciprofloxacin, Moxifloxacin, Levofloxacin(thinkCiprofloxaquin, Moxifloxaquin etc) Act on DNAGyrase Active mostly against Gram negatives – use for UTIs, bacterial gastroenteritis Nitroimidazoles – Metronidazole Useful against anaerobes and protozoa Nitrofurantoin - UTIs Recap:

  31. A. Cell wall synthesis inhibitors β-lactams 1. Penicillins Crossreactivity – caution if hx anaphylaxis 2. Cephalosporins 1st generation – gram + > - 2nd generation – gram + and - 3rd generation – gram - > + - have T in them – T for ‘third’ cefotaxime, ceftazidime, ceftriaxone 3. Carbapenems B R O A D spectrum Recap: Glycopeptides Require therapeutic drug monitoring (TDM) 1. Vancomycin Usually IV – covers MOST GRAM + incl MRSA - but NOT VRE! Exception - oral vancomycin – for C. Difficile diarrhoea (where metronidazolehas failed) 2. Teicoplanin Vancomycin – negligible systemic absorption – used ORALLY for C. Diff

  32. Gastro – Clostridium difficile Relative risk (RR) of developing Clostridium difficile following antibiotic therapy: Clindamycin: RR = 31.8 Cephalosporins: RR = 14.9 Ciprofloxacin: RR = 5.0 Second and third generation cephalosporins more assoc with C. Difficile than first generation www.passmedicine.com

  33. Protozoa in Gastroenteritis

  34. C. Inhibitors of DNA synthesis Quinolones – Ciprofloxacin, Moxifloxacin, Levofloxacin(thinkCiprofloxaquin, Moxifloxaquin etc) Act on DNAGyrase Active mostly against Gram negatives – use for UTIs, bacterial gastroenteritis Nitroimidazoles – Metronidazole Useful againstanaerobesand protozoa Nitrofurantoin - UTIs Recap:

  35. Protozoa in Gastroenteritis

  36. GI EMQ 1 A 24-year old medical student preparing for his finals reports a 4 week history of abdominal pain, foul-smelling greasy diarrhoea and increased flatulence. Please choose one answer from the adjacent list • Salmonella enteritidis • Salmonella typhi • Shigella • ETEC • EHEC • EIEC • Vibrio cholerae • Giardia Lamblia • Entamoeba Histolytica • Campylobacter Jejuni • Bacillus Cereus • Clostridium difficile • Clostridium perfringens • Rotavirus • Norovirus

  37. GI EMQ 2 An 18-year old Imperial student comes to the GP with a 4 hour history of vomiting, which began at lunchtime. He wonders if it might be related to the leftovers he had for breakfast that morning following his Chinese New Year celebrations last night. Please choose one answer from the adjacent list • Salmonella enteritidis • Salmonella typhi • Shigella • ETEC • EHEC • EIEC • Vibrio cholerae • Giardia Lamblia • Entamoeba Histolytica • Campylobacter Jejuni • Bacillus Cereus • Clostridium difficile • Clostridium perfringens • Rotavirus • Norovirus

  38. GI EMQ 3 A 40-year-old female patient reports loose stools for a week ever since returning from Morocco last week. She otherwise feels well. Please choose one answer from the adjacent list • Salmonella enteritidis • Salmonella typhi • Shigella • ETEC • EHEC • EIEC • Vibrio cholerae • Giardia Lamblia • Entamoeba Histolytica • Campylobacter Jejuni • Bacillus Cereus • Clostridium difficile • Clostridium perfringens • Rotavirus • Norovirus

  39. GI EMQ 4 A 25-year-old patient comes to see the clinic you are running whilst on your elective. She reports a lengthy history of bloody diarrhoea and weight loss. On examination, her abdomen is soft but tender, particularly in the right upper quadrant. Please choose one answer from the adjacent list • Salmonella enteritidis • Salmonella typhi • Shigella • ETEC • EHEC • EIEC • Vibrio cholerae • Giardia Lamblia • Entamoeba Histolytica • Campylobacter Jejuni • Bacillus Cereus • Clostridium difficile • Clostridium perfringens • Rotavirus • Norovirus

  40. Gastro/Hepatology • Diarrhoea and vomiting • Hepatitis

  41. Viral hepatitis SBA: Which one of the following statements best describes the prevention and treatment of hepatitis C?A.No vaccine is available and treatment is only successful in around 10-15% of patients B.No vaccine and no treatment is available C. A vaccine is available and treatment is successful in around 50% of patients D. A vaccine is available but no treatment has been shown to be effective E.No vaccine is available but treatment is successful in around 50% of patients

  42. Hepatitis B vs C

  43. Hep B You wish to screen a patient for hepatitis B infection. Which one of the following is the most suitable test to perform?A. HBcAg B. HBsAg C. Hepatitis B viral load D. anti-HBs E. HBeAg

  44. Hepatitis B serology

  45. Hepatitis B serology

  46. Hepatitis B serology

  47. Hepatitis A, D, E Hepatitis A, E – faecal-oral transmission Hepatitis D – co-infects patients already infected with Hepatitis B

  48. Urinary Tract

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