Dysentery: Causes, Pathophysiology, Risk Factors, and Treatment

Dysentery = inflammatory diarrhea with visible blood and mucus, caused by invasive pathogens damaging the colonic mucosa.

Major Etiologies

• Shigella spp. (S. dysenteriae type 1 = most severe) — Shiga toxin → endothelial damage, HUS risk.
• Campylobacter jejuni — common foodborne; can trigger Guillain-Barré.
• Salmonella (non-typhoidal) — invasive strains.
• Entamoeba histolytica — amoebic dysentery; flask-shaped ulcers; liver abscess risk.
• EIEC (enteroinvasive E. coli) — Shigella-like.

Transmission

Fecal-oral: contaminated water/food, person-to-person (poor hygiene), fomites. Outbreaks in crowding, poor sanitation, travelers.

Pathophysiology

Pathogens invade colonic epithelium → inflammation, ulceration, exudation of blood/mucus, impaired absorption → frequent small-volume bloody stools, tenesmus, abdominal cramps, fever.

Risk Groups

• Children <5, elderly, immunocompromised
• Travelers to endemic areas
• MSM (Shigella, amebiasis)

Diagnosis

• Stool culture, PCR multiplex panel, O&P (ova & parasites), antigen tests.

Treatment

• Bacterial: Azithromycin (Shigella, Campylobacter), fluoroquinolones (adults), ceftriaxone (severe). Avoid antimotility agents if bloody/febrile.
• Amoebic: Metronidazole 750 mg TID × 7–10 d → paromomycin (luminal agent) to eradicate cysts.
• Supportive: ORS/IV fluids, electrolyte correction.

Prevention

Safe water, hand hygiene, food safety, sanitation. No licensed Shigella vaccine yet.