GI micbio

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GI micbio
2013-06-16 22:42:25

Helicobacter pylori
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  1. Bacteriology of helicobacter pylori
    • Gram Negative
    • Spiral-shaped bacterium
    • With 4-6 unipolar flagellae
    • Microaerophilic (5% O2)
    • Strongly urease positive
  2. Prevalence of H. pylori
    • Global prevalence >50%
    • developing countries > developed countries
  3. Mode of transmission of H. pylori
    • **Person-to-person
    • Gatro-oral
    • Faeco-oral
    • Oro-oral
    • Nosocomial due to contaminated endoscopes
    • Drinking water and food
  4. Risk factors of H. pylori
    • Poor socio-economical development
    • Low education
    • Poor hygiene condition in childhood
    • Crowded families
    • Absence of sanitary drinking water
    • Absence of sewage disposal facilities
  5. Pathology of H. pylori
    Chronic infection à chronic superficial gastritis + atrophy
  6. Foci of infection of H. pylori
    • Gastric antral epithelium and foci of peptic ulceration
    • Found in mucus gel layer over gastric epithelium and some may invade intracellularly into the epithelial cells and into lamina propria
  7. Virulence factors of H. pylori
    • Colonization: urease, motility, adherence
    • Persistence: inaccessibility to immune attack
    • Altered gastric physiology
    • Vacuolating cytotoxin (vacA gene), cytotoxin-associated gene A protein (cagA gene) à tissue injury and carcinogenesis
  8. 4 Diseases in Stomach caused by H. pylori
    • Chronic superficial gastritis
    • Peptic ulcer
    • Gastric adenocarcinoma of body and antrum
    • Gastric MALT lymphoma (mucosa-associated lymphoid tissue- type low grade B cell lymphoma)
  9. 5 types of diagnosis of H. pylori infection
    • BUSHA
    • Bacteriological diagnosis ** for antibiotic sensitivity test
    • Urease-based test
    • Stool antigen detection test
    • Histopathological diagnosis
    • Antibody detection **for epidemiological studies
  10. What is the sample taken for bacteriological diagnosis of H. pylori infection?
    Endoscopic gastric mucosal biopsies transported in sterile saline in microaerophilic culture à may give rise to sampling error
  11. What to look for in histopathological diagnosis of H. pylori infection?
    • Morphology
    • Position
    • Diffuse distribution
    • Presence of inflammation
  12. Special stain for H. pylori
    Warthin-Starry stain
  13. What are the samples for serology looking for H. pylori infection?
    • Urine
    • Saliva
    • Blood
  14. What’s the difference between enzyme immunoassay and immunochromatographic assays in stool antigen detection tests for diagnosis of H. pylori?
    • EIA: lab-based using monoclonal antibodies + better accuracy
    • Immunochromatographic assays: rapid in office setting + relatively low sensitivity
  15. What are the two types of urease-based tests?
    • Rapid urease test (using biopsies of gastric mucosa)
    • urea breath test
  16. What’s the difference between eradication and clearance?
    • Clearance = absence of detectable organisms immediately after stopping therapy
    • Eradication = absence of detectable organisms >/= 4 weeks after stopping therapy
  17. What are the Agents used for eradication of H. pylori?
    • Anti-ylori Can Really Make Tummy Better
    • Amoxicillin
    • PPI
    • Clarithromycin
    • Ranitidine bismuth citrate
    • Metronidazole (nitroimidazole)
    • Tetracycline
    • Bismuth
  18. Which of the eradication agents of H. pylori has resistance?
    • Nitroimidazole (e.g. metronidazole)
    • Clarithromycin
  19. What are the eradication regimens for H. pylori?
    • Triple therapy (PPI-based/ bismuth-based)
    • Ranitidine bismuth citrate-based therapy
    • Quadruple therapy and second-/third-line treatment
    • Sequential therapy
  20. What is triple therapy?
    • PPI-based: PPI + Clarithromycin + amoxicillin/ metronidazole (10-14 days)
    • Bismuth-based: bismuth + metronidazole + amoxicillin/ tetracycline
    • Yet both have low eradication power due to resistance to metronidazole/ clarithromycin
  21. What is ranitidine bismuth citrate-based therapy?
    Ranitidine bismuth citrate + clarithromycin + (amoxicillin/ metronidazole)
  22. What is quadruple therapy and second-/third-line treatment of H. pylori infection?
    • PPI + bismuth + two antibiotics (TM/ AC)
    • PPI + 3 antibiotics (MAC)
    • Levofaloxacin- or moxifloxacin-based regimens
  23. What is sequential therapy of H. pylori infection?
    5D of PPI + amoxicillin à 5D of PPI + C+ M
  24. What are the 4 normal intestinal defence mechanisms?
    • gastric acidity
    • intestinal motility
    • enteric normal flora -> colonization resistance
    • specific immunity
  25. What are the normal flora of the stomach?
    • alpha-hemolytic streptococci
    • lactobacilli
    • yeasts
    • swallowed oral bacteria
  26. What are the normal flora of the duodenum?
    • alpha-hemolytic streptococci
    • lactobacilli
    • transitory oral bacteria
  27. What are the normal flora of the colon?
    • enterobacteriaceae 
    • **anaerobes
  28. 4 Control measures of enteric infectios
    • public health measures
    • non-specific host factors
    • surveillance
    • vaccines
  29. Principles of therapy of infectious diarrhoea
    • Fluid replacement (oral rehydration solution ORS)
    • Antibiotics 
    • Antimotility agents (avoided in invasive infections)
  30. What are the 3 types of toxins and their respective examples?
    • secretory toxins e.g. Vibrio Colerae, enterotoxigenix E. Coli, Clostridium Perfringens
    • cytotoxins e.g. Shigella, enterohaemorrhagic E. Coli, Clostrium Difficile
    • neurotoxins e.g. Clostridium botulinum, Staphylococcus aureus, Bacillus cereus