Nontoxigenic Clostridium difficile protects hamsters against challenge with historic and epidemic strains of toxigenic BI/NAP1/027 C. difficile.

Nontoxigenic Clostridium difficile (NTCD) has been shown to prevent fatal C. difficile infection in the hamster model when hamsters are challenged with standard toxigenic C. difficile strains. The purpose of this study was to determine if NTCD can prevent C. difficile infection in the hamster model when hamsters are challenged with restriction endonuclease analysis group BI C. difficile strains. Groups of 10 hamsters were given oral clindamycin, followed on day 2 by 10(6) CFU of spores of NTCD strain M3 or T7, and were challenged on day 5 with 100 CFU of spores of BI1 or BI6. To conserve animals, results for control hamsters challenged with BI1 or BI6 from the present study and controls from previous identical experiments were combined for statistical comparisons. NTCD strains M3 and T7 achieved 100% colonization and were 100% protective against challenge with BI1 (P ≤ 0.001). M3 colonized 9/10 hamsters and protected against BI6 challenge in the colonized hamsters (P = 0.0003). T7 colonized 10/10 hamsters, but following BI6 challenge, cocolonization occurred in 5 hamsters, 4 of which died, for protection of 6/10 animals (P = 0.02). NTCD colonization provides protection against challenge with toxigenic BI group strains. M3 is more effective than T7 in preventing C. difficile infection caused by the BI6 epidemic strain. Prevention of C. difficile infection caused by the epidemic BI6 strain may be more challenging than that of infections caused by historic BI1 and non-BI C. difficile strains.