Campylobacter jejuni

C. jejuni - The Gutsy Glider

• Gram-negative, motile, curved (S-shaped or “gull-wing”) rod; oxidase ⊕.
• Thrives in heat (thermophilic) at 42°C and low oxygen (microaerophilic).
• Source: Undercooked poultry, unpasteurized milk, pets (puppies).
• Clinical: Common cause of invasive, inflammatory, bloody diarrhea.

⭐ Guillain-Barré Syndrome (GBS): Ascending paralysis triggered by autoimmune cross-reactivity with lipooligosaccharides. A major post-infectious sequela.

Pathogenesis - Invasion Games

• Adhesion & Motility: Utilizes adhesin protein CadF to bind to fibronectin and polar flagella for corkscrew motility to penetrate intestinal mucus.
• Invasion: Invades enterocytes in the jejunum, ileum, and colon via endocytosis, surviving within vacuoles.
• Toxin-Mediated Damage: Releases Cytolethal Distending Toxin (CDT), an A-B toxin.
  • CDT's B subunit binds to the cell.
  • CDT's A subunit (CdtB) acts as a DNase, causing dsDNA breaks, leading to cell cycle arrest in G2/M phase and apoptosis.

⭐ Molecular Mimicry: C. jejuni's lipooligosaccharide (LOS) can mimic human gangliosides (e.g., GM1), triggering autoimmune cross-reactivity that leads to Guillain-Barré syndrome (GBS).

Clinical Features - Gut Punch & Nerve Pinch

• Gastroenteritis (Acute Enteritis):

  • Incubation: 1-3 days.
  • Prodrome: Fever, headache, myalgias.
  • Main symptoms: Severe, crampy abdominal pain (can mimic appendicitis) followed by profuse, watery, and frequently bloody diarrhea (≥10 stools/day).
  • Usually self-limiting within one week.

• Post-Infectious Sequelae (1-3 weeks post-infection):

  ⭐ Campylobacter jejuni is the most common infectious precipitant of Guillain-Barré syndrome (GBS). The mechanism involves molecular mimicry between bacterial lipooligosaccharides and peripheral nerve gangliosides (anti-GM1 antibodies).

  • Guillain-Barré Syndrome: Acute, ascending, symmetric flaccid paralysis with ↓ or absent deep tendon reflexes (areflexia).
  • Reactive Arthritis: Asymmetric oligoarthritis, urethritis, conjunctivitis. Strong HLA-B27 association. 📌 "Can't see, can't pee, can't climb a tree."

Diagnosis & Treatment - Lab Hunt & Drug War

• Lab Diagnosis
  • Stool Culture: Gold standard, requires special conditions.
    • Grows at 42°C (thermophilic).
    • Microaerophilic (↑CO₂, ↓O₂).
    • Media: Skirrow's agar, Campy BAP.
  • Microscopy: Gram-negative, motile, S-shaped or "gull-wing" rods.
  • Biochemical: Oxidase-positive.
• Treatment
  • Mainstay: Supportive care (rehydration).
  • Severe Disease: Macrolides (e.g., Azithromycin).
  • ⚠️ High rates of fluoroquinolone resistance.

⭐ Campylobacter jejuni is the most common infectious antecedent to Guillain-Barré syndrome (GBS).

High‑Yield Points - ⚡ Biggest Takeaways

• Most common bacterial cause of gastroenteritis in developed countries, frequently from undercooked poultry.
• A curved, Gram-negative rod that is oxidase-positive and thrives at 42°C (thermophilic).
• Presents with fever, cramping abdominal pain, and inflammatory bloody diarrhea.
• Strongly associated with post-infectious Guillain-Barré syndrome (GBS) due to molecular mimicry.
• Can also lead to reactive arthritis as a long-term complication.
• Usually self-limited; macrolides are reserved for severe or prolonged illness.