Aetiology of antimicrobial-agent-associated colitis.

Clostridium difficile was isolated from the faeces of a patient with clindamycin-associated pseudomembranous colitis (P.M.C.). The presence of a preformed faecal toxin and the toxigenicity of both the faecal isolate of C. difficile and a reference strain of C. difficile were demonstrated by tissue-culture assay. The toxin of both strains of C. difficile and that in the patient's faeces were neutralised by heating and by incubation with antitoxin to C. sordellii, but not by incubation with antitoxin to C. histolyticum, C. oedematiens (novyi), C. welchii (C. perfringens) or C. septicum. These data implicate the toxin of C. difficile as a major, and perhaps the sole, cause of antimicrobial-agent-associated P.M.C. of man and suggest that the neutralisation of the faecal toxin of P.M.C. by C. sordellii antitoxin, as described by other investigators, may be a non-specific phenomenon.