Applied Biosafety

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.

The aim of this study was to quantify microbiologically the operator protection factor (OPF) and measure the extent of cross-contamination provided by a new Advisory Committee on Dangerous Pathogens (ACDP) containment level 4 cabinet line system (glove box line). To accomplish this goal, the cabinet line was filled with microbial tracer aerosol, and microbial air samplers were used to detect any release of microbial tracer, both inside and outside the cabinet line when procedures were carried out. These procedures mimicked normal working conditions and realistic accident scenarios. The operator protection factors (OPFs) and internal cross-contamination ratios were calculated.

The cabinet line gave OPFs of between >10⁶ and >10⁷ in all tests. No cross-contamination was detected when internal doors remained closed between the individual cabinets and the spine. However, low levels of microbial tracer were detected moving from the contaminated cabinet to the spine but not to other individual cabinets when cabinet doors were opened.

These experiments demonstrated that the cabinet line provides a high level of protection for the operator and that multi-agents can be manipulated simultaneously within the cabinet line without cross-contamination. In addition, data have been produced, within a large primary containment system, from which informed risk assessments and procedures can be written. Such data provide a basis with which to compare primary containment with alternative ways of working with dangerous pathogens, such as positive pressure-suited systems.

The disposal of microbiologically contaminated or potentially contaminated liquid waste is an important consideration for research facilities and other installations. Traditional methods include batch steam sterilization and chemical, thermo-chemical, or thermal disinfection kill-tanks. This report describes a new continuous effluent decontamination system that allows for the continuous collection, thermal sterilization, and cool-down of waste water prior to discarding from the facility. The verification of the safety, efficacy, and maintenance of the process required the development of specific microbiological test methods, which are described and discussed. The benefits of and considerations for using the system for liquid waste treatment and disposal–in comparison to traditional kill tanks—are discussed.