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Clostridioides difficile is a gram-positive, spore-forming anaerobic bacterium that causes antibiotic-associated colitis and pseudomembranous colitis. C. difficile infection (CDI) is the leading cause of healthcare-associated infectious diarrhea and can range from mild diarrhea to life-threatening toxic megacolon. Risk factors include recent antibiotic use, advanced age, hospitalization, and immunosuppression.
C. difficile produces two major toxins (TcdA and TcdB) that cause epithelial cell damage, inflammation, and increased intestinal permeability. The organism typically establishes infection after normal colonic flora is disrupted by antibiotics, allowing C. difficile spores to germinate and proliferate. Toxin production leads to colonic inflammation, fluid secretion, and in severe cases, pseudomembrane formation consisting of inflammatory debris and fibrin.
Diagnosis is based on clinical presentation of diarrhea (≥3 loose stools in 24 hours) with recent antibiotic exposure, combined with positive stool testing for C. difficile toxins or toxigenic organisms. Treatment involves discontinuing inciting antibiotics when possible and initiating targeted therapy with oral vancomycin or fidaxomicin for initial episodes. Severe cases may require IV metronidazole, higher vancomycin doses, or surgical intervention, while recurrent infections may benefit from fecal microbiota transplantation.