title: Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores.
abstract: Decontamination studies investigating the effectiveness of products and processes for the inactivation of Bacillus species spores have traditionally utilized metering viable spores in a liquid suspension onto test materials (coupons). The current study addresses the representativeness of studies using this type of inoculation method compared to when coupons are dosed with a metered amount of aerosolized spores. The understanding of this comparability is important in order to assess the representativeness of such laboratory-based testing when deciding upon decontamination options for use against Bacillus anthracis spores. Temporal inactivation of B. anthracis surrogate (B. subtilis) spores on representative materials using fumigation with chlorine dioxide, spraying of a pH-adjusted bleach solution, or immersion in the solution was investigated as a function of inoculation method (liquid suspension or aerosol dosing). Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations. Differences were mostly noted for the materials observed to be more difficult to decontaminate (i.e., wood and carpet). Significant differences in measured effectiveness were also noted to be a function of the pH-adjusted bleach application method used in the testing (spray or immersion). Based upon this work and the cited literature, it is clear that inoculation method, decontaminant application method, and handling of non-detects (i.e., or detection limits) can have an impact on the sporicidal efficacy measurements.
authors.affiliation: US EPA, Office of Research and Development, National Homeland Security Research Center, MD E343-06; 109 TW Alexander Dr., Research Triangle Park, NC, 27711, USA, ryan.shawn@epa.gov.
authors.forename: Shawn P
authors.initials: SP
authors.lastname: Ryan
authors.forename: Sang Don
authors.initials: SD
authors.lastname: Lee
authors.forename: M Worth
authors.initials: MW
authors.lastname: Calfee
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Wood
authors.forename: Stella
authors.initials: S
authors.lastname: McDonald
authors.forename: Matt
authors.initials: M
authors.lastname: Clayton
authors.forename: Nicole
authors.initials: N
authors.lastname: Griffin-Gatchalian
authors.forename: Abderrahmane
authors.initials: A
authors.lastname: Touati
authors.forename: Luther
authors.initials: L
authors.lastname: Smith
authors.forename: Melissa
authors.initials: M
authors.lastname: Nysewander
mesh_terms: D000336:Aerosols; D001412:Bacillus subtilis / Q000187:drug effects* / Q000502:physiology*; D057886:Bleaching Agents / Q000494:pharmacology; D017606:Chlorine Compounds / Q000494:pharmacology; D003666:Decontamination / Q000379:methods*; D004202:Disinfectants / Q000494:pharmacology; D004866:Equipment Contamination; D005651:Fumigation; D006863:Hydrogen-Ion Concentration; D010087:Oxides / Q000494:pharmacology; D013171:Spores, Bacterial / Q000187:drug effects
chemical_list: D000336:Aerosols; D057886:Bleaching Agents; D017606:Chlorine Compounds; D004202:Disinfectants; D010087:Oxides; C025109:chlorine dioxide