Fig. 4
Epidemic ribotype isolates of C. difficile are more virulent than non-epidemic isolates in the hamster model of CDI. For each isolate, groups (n = 5) were orally inoculated with a titration range of C. difficile spores as needed to define the LD50. a The graph compares the mean survival of each group inoculated with either non-epidemic or epidemic strains at specific log10 spore titers. Error bars represent the standard deviation of mean survival percentages at specific spore titers, and average LD50 values were calculated for each group with the variable slope model (Y = 100/ (1 + 10^((LogEC50 – x) * HillSlope))) and were determined to be significantly different using the extra sum-of-squares F test (p < 0.05). b The individual LD50 values for epidemic and nonepidemic ribotype isolates are shown. An asterisk denotes significant difference at p ≤ 0.05 (Student’s unpaired t test)