FIG 1.

Germination and outgrowth of C. difficile spores in C. difficile brucella broth with thioglycolic acid and l-cystine (CDBB-TC) under aerobic culture conditions versus C. difficile brucella broth (CDBB) under anaerobic culture conditions. At time zero, 10⁴ CFU/ml of spores were added to the medium and incubated at 37°C. The aliquots were removed at the specified time points and diluted 1:1 in either phosphate-buffered saline (PBS) or absolute ethanol, serially diluted in PBS, and plated on prereduced selective plates inside an anaerobic chamber. The ethanol-shock method provides a measurement of the spore concentration, whereas the samples diluted in PBS provide a measurement of the total C. difficile count. The data shown are for C. difficile strain VA 17, an epidemic restriction endonuclease analysis (REA) type BI strain; similar results were obtained for C. difficile strain VA 11. Error bars indicate standard errors.