Bacillus AnthracisSpore Inactivation by Fumigant Decontamination

Abstract

In 2001, envelopes containing virulent Bacillus anthracis spores were placed into the U.S. mail, resulting in contamination of mail processing and distribution facilities and office buildings. These spore-contaminated facilities were subsequently decontaminated primarily by fumigation with hydrogen peroxide, chlorine dioxide, and formaldehyde. These highly-publicized incidents resulted in increased public awareness of the threat to human health posed by Bacillus anthracis, and increased interest in sampling, detection, and decontamination of indoor surfaces, rooms, and buildings. Fumigants offer advantages over liquid application for decontaminating rooms or buildings due to the increased coverage of large surface areas and ease of cleanup. From 2001 to the present, however, no decontamination technology has been registered by the U.S. Environmental Protection Agency (EPA) for use against B. anthracis spores; rather, decontamination has been performed through the EPA's issuance of Crisis Exemptions. Since 2001, research and testing efforts have assessed the efficacy and maturity of sporicidal fumigants as well as the maturity, chemical toxicity, material compatibility, and ventilation requirements of these technologies. Several studies have been published in the scientific literature regarding fumigant inactivation of Bacillus spores; however, most decontamination studies with fumigants have utilized surrogates for B. anthracis surrogates, which can be more resistant to a specific type of fumigant (e.g., Geobacillus stearothermophilus and vaporous hydrogen peroxide) than virulent B. anthracis. Therefore, the purpose of this review is to summarize current knowledge available in the open scientific literature describing the inactivation of virulent B. anthracis spores by various fumigating agents with respect to key operational variables that can affect fumigant decontamination efficacy, such as fumigant concentration, contact time, operational temperature, and relative humidity.

Gaseous Decontamination Methods in High-containment Laboratories

“…Porous materials have also been found to require extended aeration periods after decontamination due to the occurrence of off gassing (Davies et al, 2010). A large amount of data has shown VHP/HPV to be compatible with a wide variety of materials although some studies have indicated it is incompatible with nylon, neoprenes, some anodized aluminum, and some epoxides (Davies et al, 2010;Rogers et al, 2008a). Decontaminations occurring in laboratories containing sensitive equipment, such as computers, cameras, incubators, and other heat-sensitive equipment, have indicated VHP/HPV is compatible with such equipment without any damaging effects (Davies et al, 2010;Hall et al, 2007;Heckert et al, 1997;Krause et al, 2001).…”

“…Conversely, organisms on nonporous materials such as glass and stainless steel were found to require much shorter inactivation times (Han et al, 2003;Krishnan et al, 2006b;Rastogi et al, 2009;Rastogi et al, 2010). Material compatibility studies have found GCD to be compatible with most materials such as paper, wood, epoxy, plastics, and stainless steel, but do indicate bleaching of some materials such as carpet (Rogers et al, 2008a). Further, when GCD is generated by off gassing from liquid chlorine dioxide, corrosion of non-coated metal surfaces was observed after repeated exposure .…”

“…Hydrogen peroxide is considered less toxic as it readily breaks down into water and oxygen with no toxic by-products or residues (Davies et al, 2010;Rogers et al, 2008a). The VHP/HPV decontamination technology also allows automated cycles and the ability to control and monitor conditions of the decontamination area, thus increasing the safety of the users.…”

“…One of the greatest disadvantages of formaldehyde gas is its negative effect on the environment due to its toxic properties. Formaldehyde gas is a known human carcinogen and is not environmentally friendly (Abraham, 2004;Rogers et al, 2008a). The negative environmental effects of this gas may limit where this procedure can be performed.…”

“…In these situations, liquid disinfectant wipe-down techniques can be time-consuming and difficult to standardize and may simply not be feasible (Krause et al, 2001). In these cases, gas decontamination methods are advantageous because of their ability to cover large surface areas and more difficult to reach areas (Rogers et al, 2008a).…”