Clostridium difficile colitis.

Clostridium difficile has become one of the commonest pathogens of the lower intestinal tract. This organism appears unique in that infection almost always occurs during or after antibiotic therapy, suggesting that some component of the normal microflora prevents colonization by C. difficile. Once it has overgrown in the colon, C. difficile releases several toxins which cause tissue damage and diarrhea. Infection can range from a simple self-limited diarrheal illness to fulminant colitis with perforation and megacolon. Assay of stool filtrates reveals the presence of cytotoxin in nearly all patients with antibiotic-associated pseudomembranous colitis, and in approximately one third to one half of those with less severe infections. Effective therapy is available in the form of oral vancomycin, although the expense of this antibiotic has led to the use of oral metronidazole or bacitracin, which appear to be equally efficacious and considerably cheaper. Although we have learned a great deal about C. difficile in the past decade, a number of fascinating puzzles remain. We know very little about the immune response to this organism or its toxin, or whether a vaccine might someday be feasible. Similarly, we have very little insight into what effects antibodies exert on the normal colonic flora and how these effects allow C. difficile infection in a small percentage of patients. Studies of this pathogen will undoubtedly lead to a fuller understanding of the enormously complex and still mysterious microbial ferment which lives within our gastrointestinal tract.