A Novel Approach for Conducting Room-scale Vaporous Hydrogen Peroxide Decontamination of Virulent Bacillus anthracis Spores

Studies have been conducted to determine the efficacy of various decontamination technologies against virulent B. anthracis and surrogate spores within small, bench-scale chambers. This study assessed an approach for evaluating room-scale (~2,700 ft3) decontamination efficacy of vaporous hydrogen peroxide fumigation against B. anthracis Ames and B. subtilis spores deposited onto porous and non-porous indoor surface materials. Approximately 1x108 colony-forming units (CFU) of B. anthracis and B. subtilis spores were dried onto galvanized metal and ceiling tile coupons and then exposed to vaporous hydrogen peroxide. The materials contaminated with B. anthracis spores were placed inside a Class III biosafety cabinet (BSC III) that circulated vaporous hydrogen peroxide from within the decontaminated room, into and out of the BSC III. Identical materials inoculated in the same manner and at the same density with B. subtilis were placed both inside and outside of the BSC III to compare decontamination efficacy. Three fumigations were conducted using two sets of cycle parameters. The first set of cycle parameters for vaporous hydrogen peroxide exposure (10 minutes of conditioning at 12 g/min; 75 minutes of decontamination at 11 g/min) yielded log reductions in viable B. anthracis and B. subtilis spores ranging from 6.1 to 7.0 on all materials, while only 76% of the commercial biological indicators (1x106 CFU) evaluated in parallel were completely inactivated. The second set of cycle parameters (12 minutes of conditioning at 12 g/min; 104 minutes of decontamination at 8 g/min) yielded log reductions in viable B. anthracis and B. subtilis spores ranging from 6.7 to 7.4 on all materials and complete inactivation of biological indicators. These results demonstrate this method as a viable approach to assess room-scale fumigant decontamination efficacy against B. anthracis Ames spores.