FIG. 2.

C. difficile spores are inactivated by prolonged exposure to high-level hydrogen peroxide. (a) Viability of C. difficile M68 spores after exposure to 1% or 10% hydrogen peroxide for 1, 10, and 20 min. Data are representative of three separate experiments. Error bars indicate standard deviations. The broken horizontal line indicates the detection limit of 2 CFU/ml. (b) Spore strips containing either 10⁶ C. difficile M68 or G. stearothermophilus spores were exposed to 400 ppm hydrogen peroxide vapor for 1, 5, 20, or 60 min prior to culture of the bacteria to determine the efficacy of disinfection. Positive growth strip indicates that the spores were not inactivated by HPV. Six spore strips were tested per time point.