ABSTRACT
Aims: To determine the anti-cytotoxic effects of Lactobacillus rhamnosus GG (LGG) against extracellular and intracellular Clostridium difficile toxins. Study Design: Co-culture system. Place and Duration of Study: Division of Infectious Diseases, Department of Medicine, School of Medicine and Public Health and Department of Pathobiological Sciences, School of Veterinary Medicine, Madison, Wisconsin, between April 2010 and August 2011. Methodology: In this study, we investigated the effects of a probiotic LGG (Culturelle®) against a toxigenic C. difficile strain (ATCC 9689) and a non-toxigenic C. difficile strain (ATCC 700057) in a co-culture system. Co-cultures were prepared with 3 ml of 1:10, 1:100 or 1:1000 dilution of an overnight culture of LGG and 2 ml of 1:100 dilution of either the toxigenic or the non-toxigenic strain. Cytotoxic effects of cell-free culture supernatants (CFS) and cell lysates of the toxigenic strain on Vero cells were evaluated after coculturing. The relative abundance of toxin A (TcdA) and Toxin B (TcdB) genes in 72 h cocultures were determined using real time PCR. Results: In co-cultures with 1:10 or 1:100 dilution of LGG, counts of the toxigenic C. difficile strain were about one log unit lower than control pure cultures after incubation for 48 h. In all co-cultures, counts of the non-toxigenic strain were two log units lower than those of controls. Accordingly, LGG resulted in a significant decrease (p < 0.05) in the relative abundance of TcdA and TcdB in target DNA prepared from co-cultures containing the 1:10 or the 1:100 dilution of the probiotic. Co-culturing the toxigenic strain with the probiotic (1:10 and 1:100) decreased (P < 0.05) the cytotoxic effect of both extracellular and intracellular clostridial toxins resulting in up to 30% increase in cell viability. Conclusion: LGG inhibits the growth of C. difficile in a dose-dependent manner and protects cells from C. difficile induced cytotoxicity.