Presence of Clostridium difficile toxin in guinea pigs with penicillin-associated colitis

Cecal filtrates from guinea pigs treated with penicillin contained a toxin which produced cytotoxic changes in HeLa cell cultures and was lethal to guinea pigs when administered intracecally. The cytotoxicity could be neutralized by Clostridium difficile and C. sordellii antitoxins, but not by other clostridial antitoxins. Rabbit immunization with toxic cecal extracts produced antibody which neutralized the cytotoxicity of guinea pig cecal extracts, of stool extracts from humans with antibiotic-associated colitis and of culture supernatant fluids of C. difficile. Treatment with vancomycin reduced the number of deaths and increased the survival time of penicillin-treated animals. No cytotoxin was present in cecal extracts from these guinea pigs. Gram-negative bacteremia was present in half the penicillin-treated animals, the sick ones as well as the healthy ones. Treatment with vancomycin did not decrease the incidence of bacteremia. Gram-negative bacteremia and changes in fecal flora were observed in some antibiotic-treated guinea pigs; all diseased animals, however, contained this cytotoxin. C. difficile was isolated from cecal contents of sick animals and these isolates produced the cytotoxin in vitro. The results suggest that C. difficile toxin can cause antibiotic-associated colitis in guinea pigs.