Makindo Medical Notes

📖 About

• Shigellosis (Bacillary Dysentery) is caused by Shigella spp. 🦠
• Transmission: Primarily faecal–oral route, often via contaminated hands, food, or water.

🌍 Epidemiology

• Endemic in tropical regions with poor sanitation.
• Outbreaks occur in closed communities: schools, care homes, prisons, military barracks.
• Highly infectious → as few as 10 organisms can cause disease.
• Hand hygiene is the most effective preventive measure 🧼.

🧬 Aetiology

• Gram-negative rods; highly acid-resistant.
• Invade colonic epithelial cells → mucosal ulceration & inflammation.
• Produce cytotoxins (e.g. Shiga toxin in S. dysenteriae) → colitis, systemic effects.

🔎 Microbiology

• S. dysenteriae → most severe, toxin-mediated, may be fatal in 48 h.
• S. flexneri → common in developing countries.
• S. boydii → less frequent.
• S. sonnei → mildest disease, common in the UK & developed countries.

⚠️ Exam pearl: S. sonnei = mild, self-limiting; S. dysenteriae = severe, fulminant, may cause HUS or death.

🩺 Clinical Features

• Acute watery diarrhoea, abdominal cramps, fever, malaise.
• Progresses to bloody diarrhoea, mucus, and tenesmus (“dysentery”).
• Vomiting in ~⅓ of cases.
• Usually self-limiting (3–7 days).

⚠️ Complications

• Rectal prolapse.
• Toxic megacolon / bowel obstruction.
• Reactive arthritis (Reiter’s syndrome) → esp. HLA-B27 positive.
• Haemolytic uraemic syndrome (HUS) → Shiga toxin effect.

🧾 Differential Diagnosis

• Inflammatory bowel disease (ulcerative colitis, Crohn’s colitis).
• Amoebic dysentery (Entamoeba histolytica).
• Campylobacter or Salmonella enteritis.

🔬 Investigations

• Stool culture → confirms diagnosis, identifies species, antibiotic sensitivity.
• Sigmoidoscopy (severe cases) → erythema, ulcers, pseudomembranes.
• Bloods: may show ↑ WCC, dehydration, electrolyte disturbance.

💊 Management

• 🧼 Hand hygiene → key to prevention & outbreak control.
• 💧 Rehydration: ORS for mild/moderate; IV fluids if severe dehydration.
• 💊 Antibiotics: Indicated in severe disease, outbreaks, immunocompromised, or healthcare settings.
  • First-line (UK): Ciprofloxacin 500 mg BD × 3 days.
  • Alternatives if resistant: Azithromycin or Ceftriaxone (guided by culture).
• ⛔ Avoid antimotility agents (loperamide) → risk of prolonging illness & complications.