Fig. 7.

The wild-type and prsW C. difficile strains were tested for growth or survival under various in vitro and in vivo conditions. (A) In vitro survival competition assays. Mixtures of wild-type and prsW mutant cells were exposed to water (untreated), bacitracin (0.5 mg/ml), or lysozyme (2.5 mg/ml) for 1 h. Experiments were performed on three independent days. The graph shows the results of one set of experiments (n=5). (B) In vivo competition assays with hamsters. Mixtures of wild-type and prsW mutant cells were orally inoculated into hamsters. At 5 days postinoculation, animals were sacrificed, and relevant organs (small intestine, cecum, and colon) were removed, homogenized, and plated for C. difficile. Experiments were performed on two independent days. The graph shows results from both sets of experiments (n=8). A mixture of wild-type and prsW mutant cells was also used to inoculate fresh BHIS medium and grown overnight at 37°C for the in vitro experiment. The numbers of wild-type and prsW mutant bacteria in all competition assays were determined by dilution plating onto BHIS agar and onto BHIS agar with Erm.