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Applied and Environmental Microbiology, June 2009, p. 3688-3694, Vol. 75, No. 11
0099-2240/09/$08.00+0 doi:10.1128/AEM.02592-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Quantitative Method To Determine Sporicidal Decontamination of Building Surfaces by Gaseous Fumigants, and Issues Related to Laboratory-Scale Studies
Vipin K. Rastogi,1*
Lalena Wallace,1,
Lisa S. Smith,1,
Shawn P. Ryan,2 and
Blair Martin3
BioDefense Team, R&T Directorate, U.S. Army Edgewood Chemical Biological Center, Aberdeen Proving Grounds, Maryland 21010,1 U.S. Environmental Protection Agency, Office of Research and Development/National Homeland Security Research Center, 109 T. W. Alexander Dr., Research Triangle Park, North Carolina 27711,2 U.S. Environmental Protection Agency, Office of Research and Development/National Risk Management Research Laboratory, 109 T. W. Alexander Dr., Research Triangle Park, North Carolina 277113
Received 12 November 2008/ Accepted 27 March 2009
Chlorine dioxide gas and vaporous hydrogen peroxide sterilant have been used in the cleanup of building interiors contaminated with spores of Bacillus anthracis. A systematic study, in collaboration with the U.S. Environmental Protection Agency, was jointly undertaken by the U.S. Army-Edgewood Chemical Biological Center to determine the sporicidal efficacies of these two fumigants on six building structural materials: carpet, ceiling tile, unpainted cinder block, painted I-beam steel, painted wallboard, and unpainted pinewood. Critical issues related to high-throughput sample processing and spore recovery from porous and nonporous surfaces included (i) the extraction of spores from complex building materials, (ii) the effects of titer challenge levels on fumigant efficacy, and (iii) the impact of bioburden inclusion on spore recovery from surfaces and spore inactivation. Small pieces (1.3 by 1.3 cm of carpet, ceiling tile, wallboard, I-beam steel, and pinewood and 2.5 by 1.3 cm for cinder block) of the materials were inoculated with an aliquot of 50 µl containing the target number (1 x 106, 1 x 107, or 1 x 108) of avirulent spores of B. anthracis NNR1
1. The aliquot was dried overnight in a biosafety cabinet, and the spores were extracted by a combination of a 10-min sonication and a 2-min vortexing using 0.5% buffered peptone water as the recovery medium. No statistically significant drop in the kill efficacies of the fumigants was observed when the spore challenge level was increased from 6 log units to 8 log units, even though a general trend toward inhibition of fumigant efficacy was evident. The organic burden (0 to 5%) in the spore inoculum resulted in a statistically significant drop in spore recovery (at the 2 or 5% level). The effect on spore killing was a function of the organic bioburden amount and the material type. In summary, a high-throughput quantitative method was developed for determining the efficacies of fumigants, and the spore recoveries from five porous materials and one nonporous material ranged between 20 and 80%.
* Corresponding author. Mailing address: E-3150 Kingscreek St. N., Aberdeen Proving Grounds, MD 21010. Phone: (410) 436-4856. Fax: (410) 436-2081. E-mail: vipin.rastogi{at}us.army.mil
Published ahead of print on 3 April 2009.
L.W. and L.S.S. made equal contributions to this work.
Applied and Environmental Microbiology, June 2009, p. 3688-3694, Vol. 75, No. 11
0099-2240/09/$08.00+0 doi:10.1128/AEM.02592-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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