Colitis associated with metronidazole therapy.

A 46-year-old woman was treated with oral metronidazole for trichomonal vaginitis and developed diarrhea, which persisted for five weeks. Tissue culture assay of stool supernatant showed a cytopathic toxin that was neutralized by Clostridium sordellii antitoxin, and cultures yielded Clostridium difficile, which produced a similar or identical cytotoxin in vitro. This isolate proved sensitive to metronidazole at 0.25 microgram/ml. Prior reports have indicated that metronidazole may also be used therapeutically in patients with antibiotic-associated colitis ascribed to other agents. The patient presented here shows the enigma that the same agent used for therapy of colitis may also cause this complication.