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 l containing the target number (1 ؋ 10 6 , 1 ؋ 10 7 , or 1 ؋ 10 8 ) 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%.Biological terrorism has become a major concern in the United States since the anthrax spore-tainted letters in the fall of 2001 resulted in contamination and closure of the U.S. Postal Service Curseen-Morris Processing and Distribution Center (Brentwood Post Office), the Hart Senate Office Building, and the American Media Inc. office building in Boca Raton, FL. The contamination of infrastructure posed an unprecedented challenge of decontaminating over 20,000,000 cubic feet (ϳ1 million sq. ft.) of combined building interior space (6). The incident required concerted action from the government of the United States and the private sector to develop technologies for building interior cleanup. A number of liquid (29) and gaseous (3) products were granted crisis exemptions under the Federal Insecticide, Fungicide, and Rodenticide Act by the U.S. Environmental Protection Agency (EPA) for use as sterilants against Bacillus anthracis spores, but their application and efficacy in t...

Efficacy of chlorine dioxide (CD) gas generated by two distinct generation systems, Sabre (wet system with gas generated in water) and ClorDiSys (dry system with gas generated in air), was evaluated for inactivation of Bacillus anthracis spores on six building interior surfaces. The six building materials included carpet, acoustic ceiling tile, unpainted cinder block, painted I-beam steel, painted wallboard, and unpainted pinewood. There was no statistically significant difference in the data due to the CD generation technology at a 95% confidence level. Note that a common method of CD gas measurement was used for both wet and dry CD generation types. Doses generated by combinations of different concentrations of CD gas (500, 1,000, 1,500, or 3,000 parts per million of volume [ppmv]) and exposure times (ranging between 0.5 and 12 h) were used to evaluate the relative role of fumigant exposure period and total dose in the decontamination of building surfaces. The results showed that the time required to achieve at least a 6-log reduction in viable spores is clearly a function of the material type on which the spores are inoculated. The wood and cinder block coupons required a longer exposure time to achieve a 6-log reduction. The only material showing a clear statistical difference in rate of decay of viable spores as a function of concentration was cinder block. For all other materials, the profile of spore kill (i.e., change in number of viable spores with exposure time) was not dependent upon fumigant concentration (500 to 3,000 ppmv). The CD dose required for complete spore kill on biological indicators (typically, 1E6 spores of Bacillus atrophaeus on stainless steel) was significantly less than that required for decontamination of most of the building materials tested.

Despite the increasing prevalence of the nosocomial pathogen Acinetobacter baumannii, little is known about which genomic components contribute to clinical presentation of this important pathogen. Most whole-genome comparisons of A. baumannii have focused on specific genomic regions associated with phenotypes in a limited number of genomes. In this work, we describe the results of a whole-genome comparative analysis of 254 surveillance isolates of Acinetobacter species, 203 of which were A. baumannii, isolated from perianal swabs and sputum samples collected as part of an infection control active surveillance program at the University of Maryland Medical Center. The collection of surveillance isolates includes both carbapenem-susceptible and -resistant isolates. Based on the whole-genome phylogeny, the A. baumannii isolates collected belong to two major phylogenomic lineages. Results from multilocus sequence typing indicated that one of the major phylogenetic groups of A. baumannii was comprised solely of strains from the international clonal lineage 2. The genomic content of the A. baumannii isolates was examined using large-scale BLAST score ratio analysis to identify genes that are associated with carbapenem-susceptible and -resistant isolates, as well as genes potentially associated with the source of isolation. This analysis revealed a number of genes that were exclusive or at greater frequency in each of these classifications. This study is the most comprehensive genomic comparison of Acinetobacter isolates from a surveillance study to date and provides important information that will contribute to our understanding of the success of A. baumannii as a human pathogen. The Acinetobacter genus is comprised of 34 named species, many of which are found ubiquitously in the environment (1). The most clinically relevant species are members of what is known as the Acinetobacter calcoaceticus-baumannii (Acb) complex, which include A. baumannii, A. nosocomialis, A. pittii, and A. calcoaceticus (2). The organisms of the Acb complex are difficult to distinguish from each other using traditional culturing and molecular diagnostic methods employed in the current clinical microbiology laboratories (3). A. baumannii is the most frequently isolated Acinetobacter species in the health care setting (4), partly due to its ability to survive on abiotic surfaces for long periods of time (5), as well as its ability to rapidly develop antibiotic resistance (6). It is an important emerging nosocomial pathogen associated with common infections, multidrug resistance, and a high transmission rate within hospitals all over the world (7).Prior genomic studies of A. baumannii have mainly focused on multidrug-resistant strains and have identified key determinants associated with resistance (8-14). A genomic comparison of six clinical isolates of A. baumannii concluded that despite extensive genome-wide similarity, the resistance gene repertoire was highly variable, even in the genomically closely related isolates (10). In addition, anothe...

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