Inhibition of in vitro cell adherence of Clostridium difficile by Saccharomyces boulardii

The influence on the adherence of Clostridium difficile to Vero cells of the yeast Saccharomyces boulardii, the yeast fractions (cytoplasm and cell wall) and the culture supernatant was investigated in vitro. C. difficile adherence was significantly inhibited when bacteria were pre-incubated with the whole yeast and the cell wall fraction; this adherence inhibition was dose-dependent. The cell wall fraction also acts upon the target cultured cells inasmuch as the level of adherence was significantly decreased when Vero cells were preincubated with it. The same experiments carried out in the presence of an inhibitor of serine proteases resulted in no inhibition of bacterial adherence. These results suggest that the yeast could inhibit adherence of C. difficile to cells thanks to its proteolytic activity but also through steric hindrance.