USMLE

Helicobacter pylori

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Bacteria - Gram Negative
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  8. Pseudomonas aeruginosa: Overview
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  16. Enterohemorrhagic E. Coli (EHEC)
  17. Enterotoxigenic E. Coli (ETEC)
  18. Klebsiella pneumoniae
  19. Campylobacter jejuni
  20. Vibrio spp.
  21. Helicobacter pylori
  22. Borrelia burgdorferi (Lyme Disease)
  23. Leptospira interrogans
  24. Treponema pallidum: Overview
  25. Treponema pallidum: Diagnosis
  26. Congenital syphilis
  27. Chlamydia: Overview
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  30. Rickettsia rickettsii
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  32. Anaplasma vs. Ehrlichia
  33. Coxiella burnetii (Q fever)

Helicobacter pylori 

  • Characteristics
    • Gram negative rod
      • First test in algorithm, narrows scope of bacteria
    • Curved/spiral-shaped
    • Oxidase +
      • All gram negative curved rods are oxidase positive 
    • Urease +
      • Produces ammonia, creating alkaline environment
      • Helps H pylori survive in acidic gastric mucosa
    • Catalase +
    • Has flagella (motile)
  • Pathogenesis
    • Commonly colonizes antrum of the stomach 
      • Most often the prepyloric area (less acidic)
      • Destroys somatostatin-producing delta cells in the antrum, contributing to increased acid production
    • Increased acid production and local inflammatory reaction to bacteria causes ulcer formation
  • Presentation
    • Gastritis
      • Early manifestation of H pylori infection
      • Presents with dyspepsia, bloating, belching, and epigastric pain
      • Over time, results in potential complications
        • Atrophic chronic gastritis
        • Gastric cancer (adenocarcinoma)
        • Gastric lymphoma (MALTomas)
    • Gastric or Duodenal ulcers 
      • Increased acid production causes destruction of mucus layer, compounded with local inflammatory reaction to bacteria
      • H. pylori is the most common cause of peptic ulcers, especially in the duodenum
  • Diagnosis
    • Urea breath test
    • Fecal antigen test
    • Endoscopy with gastric biopsy 
      • H. pylori may be seen under the microscope
      • Urease may be detected from biopsy of gastric mucosa
  • Treatment
    • Triple therapy
      • Amoxicillin 
        • metronidazole is used if allergic to penicillins
      • Clarithromycin
      • Proton pump inhibitor (omeprazole)
    • Bismuth-based quadruple therapy if concerned about macrolide resistance 
      • Bismuth subcitrate, PPI, metronidazole, tetracycline