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Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores.

Ryan SP, Lee SD, Calfee MW, Wood JP, McDonald S, Clayton M, Griffin-Gatchalian N, Touati A, Smith L, Nysewander M - World J. Microbiol. Biotechnol. (2014)

Bottom Line: 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.Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations.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.

View Article: PubMed Central - PubMed

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.

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.

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Experimental setup for the pAB spray testing. a Sample tubes with modified funnels holding sample coupons. b Front and c side views of the stage holding three coupons. Despite parallax, coupons were mounted such that they were in the radial center of the opening in the spray guard
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Fig1: Experimental setup for the pAB spray testing. a Sample tubes with modified funnels holding sample coupons. b Front and c side views of the stage holding three coupons. Despite parallax, coupons were mounted such that they were in the radial center of the opening in the spray guard

Mentions: For Decontamination Method 2 (spray application of pAB), each test or blank coupon was attached to a specially designed funnel that was connected to a conical vial to retain the runoff generated during the spraying (see Fig. 1). The coupon assemblies were mounted onto a stage that accommodated three assemblies (see Fig. 1). For each material type, inoculation method and contact time, two stages were used together holding a combined five replicate test coupons and one blank coupon. On each stage, a spray guard was placed approximately one inch in front of the coupon surfaces. The spray guard contained 2.5 cm holes aligned directly in front of each coupon, and allowed the spray to impact on the intended coupon surface while avoiding inadvertent spray to the nearest neighbor. All materials were sterilized between tests, prior to use, by autoclaving (121 °C for 60 min).Fig. 1


Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores.

Ryan SP, Lee SD, Calfee MW, Wood JP, McDonald S, Clayton M, Griffin-Gatchalian N, Touati A, Smith L, Nysewander M - World J. Microbiol. Biotechnol. (2014)

Experimental setup for the pAB spray testing. a Sample tubes with modified funnels holding sample coupons. b Front and c side views of the stage holding three coupons. Despite parallax, coupons were mounted such that they were in the radial center of the opening in the spray guard
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4150995&req=5

Fig1: Experimental setup for the pAB spray testing. a Sample tubes with modified funnels holding sample coupons. b Front and c side views of the stage holding three coupons. Despite parallax, coupons were mounted such that they were in the radial center of the opening in the spray guard
Mentions: For Decontamination Method 2 (spray application of pAB), each test or blank coupon was attached to a specially designed funnel that was connected to a conical vial to retain the runoff generated during the spraying (see Fig. 1). The coupon assemblies were mounted onto a stage that accommodated three assemblies (see Fig. 1). For each material type, inoculation method and contact time, two stages were used together holding a combined five replicate test coupons and one blank coupon. On each stage, a spray guard was placed approximately one inch in front of the coupon surfaces. The spray guard contained 2.5 cm holes aligned directly in front of each coupon, and allowed the spray to impact on the intended coupon surface while avoiding inadvertent spray to the nearest neighbor. All materials were sterilized between tests, prior to use, by autoclaving (121 °C for 60 min).Fig. 1

Bottom Line: 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.Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations.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.

View Article: PubMed Central - PubMed

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.

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.

Show MeSH
Related in: MedlinePlus