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Infective colitis is inflammation of the colon caused by bacterial, viral, or parasitic pathogens, leading to mucosal injury, diarrhea, and systemic symptoms.

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It can range from mild self-limiting illness to severe life-threatening colitis (e.g., fulminant C. difficile).

Etiopathology

A. Bacterial Causes

• Enteroinvasive: Shigella, Salmonella, Campylobacter jejuni, Yersinia enterocolitica, E. coli O157:H7
• Toxin-mediated: Clostridioides difficile (pseudomembranous colitis)
• Others: Mycobacterium tuberculosis, Vibrio cholerae (secretory component but may cause colitis in prolonged infection)

B. Viral Causes

• CMV (immunocompromised)
• Adenovirus
• Rotavirus (children)

C. Parasitic Causes

• Entamoeba histolytica (amebic colitis)
• Schistosoma
• Strongyloides (immunocompromised)

Pathophysiology

• Pathogen adherence/invasion → mucosal inflammation, ulceration
• Some (e.g., E. coli O157:H7) produce toxins → hemorrhagic injury