Clostridioides difficile Infection
A bacterial infection of the colon that causes severe diarrhoea, colitis, and potentially life-threatening complications. C. difficile often occurs after antibiotic use disrupts normal gut bacteria. Vancomycin (oral formulation) is a primary treatment, highlighting its role beyond intravenous hospital use.
Technical Context
C. difficile is a spore-forming, toxin-producing anaerobic bacterium causing antibiotic-associated diarrhoea and colitis. Pathogenesis: broad-spectrum antibiotics disrupt normal colonic microbiota → C. difficile spore germination and vegetative cell proliferation → toxin A (enterotoxin) and toxin B (cytotoxin) production → colonocyte damage, inflammation, and pseudomembrane formation. Severity: ranges from mild diarrhoea to fulminant colitis with toxic megacolon (mortality approximately 5-10% overall, higher in elderly/immunocompromised). Recurrence: approximately 20-25% after first episode, increasing with each subsequent recurrence. Vancomycin oral formulation (125-500mg QID for 10-14 days) is first-line treatment for initial and recurrent CDI — oral vancomycin is not significantly absorbed, achieving high colonic concentrations. Fidaxomicin (a macrocyclic antibiotic, not a peptide) is an alternative with lower recurrence rates. CDI illustrates how peptide antibiotics can be used topically within the GI tract (oral vancomycin for local colonic effect) as well as systemically.