C. difficile toxin load in antibiotic-exposed animals receiving adoptive transfers 24 hours after C. difficile infection challenge (a). Animals weights 48 hours after infection challenge (b) and C. difficile CFU 24 hours after infection challenge (c). Engraftment of bacterial isolates in the intestinal microbiota of antibiotic-exposed animals two days following adoptive transfer of B. intestihominis, P. capillosus, B. hansenii, and/or C. scindens (d). Intestinal bacterial density (feces) from antibiotic-exposed mice administered suspensions containing 4 bacteria, C. scindens, or vehicle (PBS) as measured by quantitative RT-PCR of 16S rRNA genes (e). ****P<0.0001, ***P<0.001, **P<0.01, *P<0.05; Mann-Whitney (two-tailed) (a,b,d,e), Kruskal-Wallis with Dunn correction (c) (n=6–10 per group). Center values (mean), error bars (s.e.m.). Results were representative of at least two independent experiments. Numbers under group columns in (a) denote the number of mice with detectable engraftment of the given bacterium (out of 10 possible separately-housed animals per group) (d).