Clostridium difficile-associated diarrhea and colitis in adults. A prospective case-controlled epidemiologic study.

In a one-year period, 149 adult cases of Clostridium difficile-associated diarrhea and colitis were compared with 148 diarrhea-free controls. Eighty-seven percent were nosocomial and 75% were on surgical services. Endoscopy revealed pseudomembranes in 51% of the 109 cases in which stool cytotoxin was present, compared with 11% of the 40 cases that were culture-positive but cytotoxin-negative. Cases diagnosed only by stool culture showed essentially no differences from controls, 21% of whom had asymptomatic stool colonization. We estimate that only 20% of these cases had diarrhea due to C difficile. Compared with controls, cases diagnosed by the presence of cytotoxin or pseudomembranes were found to have been hospitalized longer at diarrhea onset, to have had more antecedent infections, and to have received clindamycin, multiple antimicrobials, and therapeutic antimicrobials more often than controls, but controls received prophylactic antimicrobials more frequently than cases. Cultures of the environment, patients, and personnel failed to detect a mechanism of acquisition.