Clostridium difficile and the aetiology of pseudomembranous colitis.

Bacterial isolates from 5 patients with pseudomembranous colitis (P.M.C.) were screened for toxin production. Strains of Clostridium from 4 patients produced in vitro a toxin similar to that found in P.M.C. faecal suspension. These were identified as C. difficile. Use of the strains from 2 patients induced a fatal enterocolitis when inoculated orally into hamsters pretreated with vancomycin. The C. difficile that produced the toxin in vitro was then re-isolated from hamster caecal contents. These findings suggest that P.M.C. results from infection with C. difficile and that previous antibiotic therapy produces susceptibility to infection.