Mucosal association by Clostridium difficile in the hamster gastrointestinal tract

For many organisms, mucosal association is an important virulence determinant. Although studied in detail for other intestinal pathogens, this aspect of pathogenicity has not been studied for Clostridium difficile. We compared the ability of an avirulent non-toxigenic strain (M-1), a highly virulent toxigenic strain (B-1), and a poorly virulent toxigenic strain (BAT) of C. difficile to adhere to different regions of the gastrointestinal tract of hamsters pre-treated with clindamycin. Strain B-1 associated with the gut mucosa significantly better than strain M-1 (p less than 0.001) for all sites other than the caecum, and achieved significantly higher levels in the caecal contents (p less than 0.001). The same was true when strain B-1 was compared with strain BAT except that there was no significant difference for the large bowel mucosa. To assess the possible role of toxin in promoting mucosal association, e.g., by compromising host defences or exposing masked adherence sites, strain M-1 was given to animals after intra-caecal administration of crude toxin preparations from strain-B1, which were heat-inactivated in control experiments. The addition of this toxin increased significantly the mucosal association of M-1 for the small bowel only, whereas the inactivated toxin had no significant effect. These results imply that there may be intrinsic differences between strains in their ability to colonise and associate with the gut mucosa, which may partly depend on their ability to produce toxin. These differences do not correlate with cell-surface hydrophobicity or the presence of plasmids, flagella or fimbriae.