A patient was hospitalized after a road accident. The wounds became infected and the patient was treated with tobramycin, carbenicillin, and clindamycin. Five days after antibiotic therapy was initiated, the patient developed severe diarrhoea and pseudomembranous enterocolitis. Antibiotic associated diarrhoea and the more serious pseudomembranous enterocolitis can be caused by

Pseudomembranous enterocolitis and antibiotic-associated diarrhea are caused by an anaerobic Gram-positive rod, Clostridium difficile. Patients treated with antibiotics develop diarrhea that, in most cases, is self-limiting. However, in some instances, paicularly in those patients treated with ampicillin or clindamycin, a severe, life-threatening pseudomembranous enterocolitis develops. This disease has characteristic histopathology, and membranous plaques can be seen in the colon by endoscopy. It has been recently shown that C. difficile produces a protein toxin with a molecular weight of about 250,000. The "toxin" is, in fact, two toxins, toxin A and toxin B. Both toxins are always present in fecal samples, but there is approximately one thousand times more toxin B than toxin A. Toxin A has enterotoxic activity--that is, it elicits a positive fluid response in ligated rabbit ileal loops-- whereas toxin B appears to be primarily a cytotoxin.