FIG. 1.

Mouse model of in vitro colonization resistance to C. difficile. Mice (n = 8 per group) received daily subcutaneous antibiotics for 4 days. Six hours or 3 days after the final antibiotic dose, cecal contents were collected, and aliquots were inoculated with 10⁴ CFU/ml of C. difficile. Samples were incubated anaerobically for 24 h and then plated onto selective media to quantify C. difficile (lower limit of detection, 2.5 log₁₀CFU/ml). Data for three strains of C. difficile were pooled. Error bars represent standard errors of the means. Pip = piperacillin. Detection of C. difficile toxin by C. difficile Tox A/B II (Wampole Laboratories) is indicated below the x axis. *, P < 0.001 versus saline.