Abstract
The ability of viable and nonviable Saccharomyces boulardii to protect gnotobiotic mice from Clostridium difficile induced mortality was tested. With the exception of irradiated S. boulardii, which retained some activity, only viable yeast protected the mice from lethality. The survival of C. difficile infected mice was dependent on the dose of the yeast provided in the drinking water. Key words: Saccharomyces boulardii, Clostridium difficile, colitis, pseudomembranous colitis, gnotobiotic mice.