Decontamination assessment of Bacillus anthracis, Bacillus subtilis, and Geobacillus stearothermophilus spores on indoor surfaces using a hydrogen peroxide gas generator

Biocide inactivation of Bacillus anthracis spores in the presence of food residues after a 10-min treatment time was investigated. Spores of nonvirulent Bacillus anthracis strains 7702, ANR-1, and 9131 were mixed with water, flour paste, whole milk, or egg yolk emulsion and dried onto stainless-steel carriers. The carriers were exposed to various concentrations of peroxyacetic acid, sodium hypochlorite (NaOCl), or hydrogen peroxide (H 2 O 2 ) for 10 min at 10, 20, or 30°C, after which time the survivors were quantified. The relationship between peroxyacetic acid concentration, H 2 O 2 concentration, and spore inactivation followed a sigmoid curve that was accurately described using a four-parameter logistic model. At 20°C, the minimum concentrations of peroxyacetic acid, H 2 O 2 , and NaOCl (as total available chlorine) predicted to inactivate 6 log 10 CFU of B. anthracis spores with no food residue present were 1.05, 23.0, and 0.78%, respectively. At 10°C, sodium hypochlorite at 5% total available chlorine did not inactivate more than 4 log 10 CFU. The presence of the food residues had only a minimal effect on peroxyacetic acid and H 2 O 2 sporicidal efficacy, but the efficacy of sodium hypochlorite was markedly inhibited by whole-milk and egg yolk residues. Sodium hypochlorite at 5% total available chlorine provided no greater than a 2-log 10 CFU reduction when spores were in the presence of egg yolk residue. This research provides new information regarding the usefulness of peroxygen biocides for B. anthracis spore inactivation when food residue is present. This work also provides guidance for adjusting decontamination procedures for food-soiled and cold surfaces.

Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Inactivation of Bacillus anthracis Spores by Liquid Biocides in the Presence of Food Residue

Hilgren

Swanson

Diez-Gonzalez

et al. 2007

“…The selection of potential surrogate species and strains of spore formers used here was based on (i) safety for handling; (ii) availability of type strains from a credible source, such as the ATCC; (iii) ability to yield relatively high titers of spores in a liquid medium from one or more commercial sources; (iv) representation from genera other than Bacillus; and (v) prior history of use as a surrogate/biological indicator (4,11,12,15). Review of the use of Bacillus subtilis and Bacillus atrophaeus strains as surrogates was complicated by the significant changes these taxa have undergone over the years, whereby strains now designated as B. atrophaeus have been referred to in the literature as "B. subtilis var.…”

Section: Hwmentioning

confidence: 99%

Identification by Quantitative Carrier Test of Surrogate Spore-Forming Bacteria To Assess Sporicidal Chemicals for Use against Bacillus anthracis

Majcher

Bernard

Sattar

2008

The spores of six strains of Bacillus anthracis (four virulent and two avirulent) were compared with those of four other types of spore-forming bacteria for their resistance to four liquid chemical sporicides (sodium hypochlorite at 5,000 ppm available chlorine, 70,000 ppm accelerated H 2 O 2 , 1,000 ppm chlorine dioxide, and 3,000 ppm peracetic acid). All test bacteria were grown in a 1:10 dilution of Columbia broth (with manganese) incubated at 37°C for 72 h. The spore suspensions, heat treated at 80°C for 10 min to rid them of any viable vegetative cells, contained 1 ؋ 10 8 to 3 ؋ 10 8 CFU/ml. The second tier of the quantitative carrier test (QCT-2), a standard of ASTM International, was used to assess for sporicidal activity, with disks (1 cm in diameter) of brushed and magnetized stainless steel as spore carriers. Each carrier, with 10 l (>10 6 CFU) of the test spore suspension in a soil load, was dried and then overlaid with 50 l of the sporicide being evaluated. The contact time at room temperature ranged from 5 to 20 min, and the arbitrarily set criterion for acceptable sporicidal activity was a reduction of >10 6 in viable spore count. Each test was repeated at least three times. In the final analysis, the spores of Bacillus licheniformis (ATCC 14580 T ) and Bacillus subtilis (ATCC 6051 T ) proved to be generally more resistant than the spores of the strains of B. anthracis tested. The use of one or both of the safe and easy-to-handle surrogates identified here should help in developing safer and more-effective sporicides and also in evaluating the field effectiveness of existing and newer formulations in the decontamination of objects and surfaces suspected of B. anthracis contamination.Bacillus anthracis, the etiologic agent of anthrax, is a sporeforming zoonotic pathogen (3). Its spores are hardy enough for weaponization and environmental dispersal (10); viable spores of the organism have been recovered after many decades from deliberately contaminated sites (6). The more-recent and malicious use of the spores of B. anthracis in the United States (14) clearly attests to the potential of this organism to cause mortality, morbidity, and general societal disruption and reemphasizes the importance of having available suitable remedial measures for countering any subsequent accidental or deliberate release of such spores.The biohazardous nature of B. anthracis mandates its handling in laboratories at biosafety level 3, also called containment level 3 (CL-3), in Canada. The availability of only a very limited number of such facilities seriously hampers experimentation with this increasingly significant pathogen, a recognized biothreat agent. This is especially true for developmental studies on decontamination agents, as such work is often conducted in settings without biosafety level 3 facilities. This study evaluated several potential bacterial surrogates for the spores of B. anthracis to enable a wider search for safer and more-effective liquid chemical sporicides to deal with the threat of anthrax. MATE...

“…In addition, it is critical that the coupons are prepared so that the inoculation is representative of contamination as it occurs in the field. Liquid inoculation protocols that use suspended spores in aqueous buffers have been the primary methods used to prepare test surfaces for biological agent decontamination and detection studies (15,16,20). Liquid inoculation methods offer advantages in that they allow relatively easy control of the number of spores and the contaminated area.…”

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confidence: 99%

Development of an Aerosol Surface Inoculation Method for Bacillus Spores

Ryan

Snyder

2011

A method was developed to deposit Bacillus subtilis spores via aerosolization onto various surface materials for biological agent decontamination and detection studies. This new method uses an apparatus coupled with a metered dose inhaler to reproducibly deposit spores onto various surfaces. A metered dose inhaler was loaded with Bacillus subtilis spores, a surrogate for Bacillus anthracis. Five different material surfaces (aluminum, galvanized steel, wood, carpet, and painted wallboard paper) were tested using this spore deposition method. This aerosolization method deposited spores at a concentration of more than 10 7 CFU per coupon (18-mm diameter) with less than a 50% coefficient of variation, showing that the aerosolization method developed in this study can deposit reproducible numbers of spores onto various surface coupons. Scanning electron microscopy was used to probe the spore deposition patterns on test coupons. The deposition patterns observed following aerosol impaction were compared to those of liquid inoculation. A physical difference in the spore deposition patterns was observed to result from the two different methods. The spore deposition method developed in this study will help prepare spore coupons via aerosolization fast and reproducibly for bench top decontamination and detection studies.In response to the 2001 Bacillus anthracis spore incidents in the United States, many studies have investigated various technologies to sample media, detect biological agents, and decontaminate materials (3,9,10,(17)(18)(19)21). These laboratory studies typically use small coupons and laboratory inoculants to simulate the materials and biological agents that occur in field events. In these studies, test coupons should have reproducible numbers of viable spores on varied surface types. In addition, it is critical that the coupons are prepared so that the inoculation is representative of contamination as it occurs in the field. Liquid inoculation protocols that use suspended spores in aqueous buffers have been the primary methods used to prepare test surfaces for biological agent decontamination and detection studies (15,16,20). Liquid inoculation methods offer advantages in that they allow relatively easy control of the number of spores and the contaminated area. However, it is unclear whether surfaces contaminated by liquid inoculation methods are representative of surfaces contaminated with aerosolized Bacillus anthracis spores. Therefore, it is necessary to investigate the impact of various spore deposition methods on Bacillus anthracis decontamination and detection studies.The conventional particle deposition method via aerosolization is comprised of an aerosol generating system, such as a particle nebulizer, to introduce the spores into a chamber and a second chamber to allow the spores to settle onto the target material surfaces. The spore surface concentrations are controlled by varying settling time and the initial aerosolized spore concentration in the chamber. tested various methods of collecting ...