Shigellosis (Bacillary Dysentery)
📖 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.
