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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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Related in: MedlinePlus

Log reduction in viable spores as a function of chlorine dioxide fumigation time. Plots show the average and standard deviation of the log of the measured CFU values at each time point on the test coupons (y) divided by the average of the positive controls (yo). The fits to the data and 95 % confidence intervals are also shown. Aerosol inoculation is in black and liquid inoculation is in gray
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Fig2: Log reduction in viable spores as a function of chlorine dioxide fumigation time. Plots show the average and standard deviation of the log of the measured CFU values at each time point on the test coupons (y) divided by the average of the positive controls (yo). The fits to the data and 95 % confidence intervals are also shown. Aerosol inoculation is in black and liquid inoculation is in gray

Mentions: The reduction in viable spores recovered from the liquid- and aerosol-inoculated test coupons was evaluated as a function of exposure time for fumigation with ClO2, spraying with pAB, or immersion in pAB. The average log of the reduction (with standard deviation) is plotted as a function of time for each of the decontamination treatments in Figs. 2, 3 and 4. Additionally, the data fits using Eq. (2) and the 95 % confidence intervals are plotted. Where confidence intervals do not overlap, significant difference in the resulting fits is suggested. The rate of decontamination can be observed in Figs. 2, 3 and 4 as the increasing magnitude of LR as a function of time.Fig. 2


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)

Log reduction in viable spores as a function of chlorine dioxide fumigation time. Plots show the average and standard deviation of the log of the measured CFU values at each time point on the test coupons (y) divided by the average of the positive controls (yo). The fits to the data and 95 % confidence intervals are also shown. Aerosol inoculation is in black and liquid inoculation is in gray
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: Log reduction in viable spores as a function of chlorine dioxide fumigation time. Plots show the average and standard deviation of the log of the measured CFU values at each time point on the test coupons (y) divided by the average of the positive controls (yo). The fits to the data and 95 % confidence intervals are also shown. Aerosol inoculation is in black and liquid inoculation is in gray
Mentions: The reduction in viable spores recovered from the liquid- and aerosol-inoculated test coupons was evaluated as a function of exposure time for fumigation with ClO2, spraying with pAB, or immersion in pAB. The average log of the reduction (with standard deviation) is plotted as a function of time for each of the decontamination treatments in Figs. 2, 3 and 4. Additionally, the data fits using Eq. (2) and the 95 % confidence intervals are plotted. Where confidence intervals do not overlap, significant difference in the resulting fits is suggested. The rate of decontamination can be observed in Figs. 2, 3 and 4 as the increasing magnitude of LR as a function of time.Fig. 2

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