Joseph P. Wood

Environmental Persistence of a Highly Pathogenic Avian Influenza (H5N1) Virus

Human cases of disease caused by highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype are rare, yet characterized with a mortality rate of approximately 60%. Tests were conducted to determine the environmental persistence of an HPAI (H5N1) virus on four materials (glass, wood, galvanized metal, and topsoil) that could act as fomites or harbor the virus. Test coupons were inoculated with the virus and exposed to one of five environmental conditions that included changes in temperature, relative humidity, and simulated sunlight. At time periods up to 13 days, the virus was extracted from each coupon, and quantified via cytopathic effects on Madin-Darby canine kidney cells. The virus was most persistent under the low temperature condition, with less than 1 log reduction on glass and steel after 13 days at low relative humidity. Thus, at these conditions, the virus would be expected to persist appreciably beyond 13 days.

Efficacy of liquid spray decontaminants for inactivation of Bacillus anthracis spores on building and outdoor materials

Aims:  To obtain data on the efficacy of various liquid and foam decontamination technologies to inactivate Bacillus anthracis Ames and Bacillus subtilis spores on building and outdoor materials.

Evaluation of peracetic acid fog for the inactivation of Bacillus anthracis spore surrogates in a large decontamination chamber

The purpose of this study was to evaluate the sporicidal (inactivation of bacterial spores) effectiveness and operation of a fogging device utilizing peracetic acid/hydrogen peroxide (PAA). Experiments were conducted in a pilot-scale 24 m(3) stainless steel chamber using either biological indicators (BIs) or bacterial spores deposited onto surfaces via aerosolization. Wipe sampling was used to recover aerosol-deposited spores from chamber surfaces and coupon materials before and after fogging to assess decontamination efficacy. Temperature, relative humidity, and hydrogen peroxide vapor levels were measured during testing to characterize the fog environment. The fog completely inactivated all BIs in a test using a 60 mL solution of PAA (22% hydrogen peroxide/4.5% peracetic acid). In tests using aerosol-deposited bacterial spores, the majority of the post-fogging spore levels per sample were less than 1 log colony forming units, with a number of samples having no detectable spores. In terms of decontamination efficacy, a 4.78 log reduction of viable spores was achieved on wood and stainless steel. Fogging of PAA solutions shows potential as a relatively easy to use decontamination technology in the event of contamination with Bacillus anthracis or other spore-forming infectious disease agents, although additional research is needed to enhance sporicidal efficacy.

Development and field testing of a mobile chlorine dioxide generation system for the decontamination of buildings contaminated with Bacillus anthracis.

The numerous buildings that became contaminated with Bacillus anthracis (the bacterium causing the disease anthrax) in 2001, and more recent B. anthracis - related events, point to the need to have effective decontamination technologies for buildings contaminated with biological threat agents. The U.S. Government developed a portable chlorine dioxide (ClO(2)) generation system to decontaminate buildings contaminated with B. anthracis spores, and this so-called mobile decontamination trailer (MDT) prototype was tested through a series of three field trials. The first test of the MDT was conducted at Fort McClellan in Anniston, AL. during October 2004. Four test attempts occurred over two weekends; however, a number of system problems resulted in termination of the activity prior to any ClO(2) introduction into the test building. After making several design enhancements and equipment changes, the MDT was subjected to a second test. During this test, extensive leak checks were made using argon and nitrogen in lieu of chlorine gas; each subsystem was checked for functionality, and the MDT was operated for 24h. This second test demonstrated the MDT flow and control systems functioned satisfactorily, and thus it was decided to proceed to a third, more challenging field trial. In the last field test, ClO(2) was generated and routed directly to the scrubber in a 12-h continuous run. Measurement of ClO(2) levels at the generator outlet showed that the desired production rate was not achieved. Additionally, only one of the two scrubbers performed adequately with regard to maintaining ClO(2) emissions below the limit. Numerous lessons were learned in the field trials of this ClO(2) decontamination technology.

Dry thermal resistance of Bacillus anthracis (Sterne) spores and spores of other Bacillus species: implications for biological agent destruction via waste incineration.

Aims:  To obtain needed data on the dry thermal resistance of Bacillus anthracis spores and other Bacillus species for waste incinerator applications.

Environmental Persistence of Bacillus anthracis and Bacillus subtilis Spores

There is a lack of data for how the viability of biological agents may degrade over time in different environments. In this study, experiments were conducted to determine the persistence of Bacillus anthracis and Bacillus subtilis spores on outdoor materials with and without exposure to simulated sunlight, using ultraviolet (UV)-A/B radiation. Spores were inoculated onto glass, wood, concrete, and topsoil and recovered after periods of 2, 14, 28, and 56 days. Recovery and inactivation kinetics for the two species were assessed for each surface material and UV exposure condition. Results suggest that with exposure to UV, decay of spore viability for both Bacillus species occurs in two phases, with an initial rapid decay, followed by a slower inactivation period. The exception was with topsoil, in which there was minimal loss of spore viability in soil over 56 days, with or without UV exposure. The greatest loss in viable spore recovery occurred on glass with UV exposure, with nearly a four log10 reduction after just two days. In most cases, B. subtilis had a slower rate of decay than B. anthracis, although less B. subtilis was recovered initially.

Effect of inoculation method on the determination of decontamination efficacy against Bacillus spores

Decontamination studies investigating the effectiveness of products and processes for the inactivation of Bacillus species spores have traditionally utilized metering viable spores in a liquid suspension onto test materials (coupons). The current study addresses the representativeness of studies using this type of inoculation method compared to when coupons are dosed with a metered amount of aerosolized spores. The understanding of this comparability is important in order to assess the representativeness of such laboratory-based testing when deciding upon decontamination options for use against Bacillus anthracis spores. Temporal inactivation of B. anthracis surrogate (B. subtilis) spores on representative materials using fumigation with chlorine dioxide, spraying of a pH-adjusted bleach solution, or immersion in the solution was investigated as a function of inoculation method (liquid suspension or aerosol dosing). Results indicated that effectiveness, measured as log reduction, was statistically significantly lower when liquid inoculation was used for some material and decontaminant combinations. Differences were mostly noted for the materials observed to be more difficult to decontaminate (i.e., wood and carpet). Significant differences in measured effectiveness were also noted to be a function of the pH-adjusted bleach application method used in the testing (spray or immersion). Based upon this work and the cited literature, it is clear that inoculation method, decontaminant application method, and handling of non-detects (i.e., or detection limits) can have an impact on the sporicidal efficacy measurements.

Adsorption of Chlorine Dioxide Gas on Activated Carbons

Abstract Research and field experience with chlorine dioxide (ClO2) gas to decontaminate structures contaminated with Bacillus anthracis spores and other microorganisms have demonstrated the effectiveness of this sterilant technology. However, because of its hazardous properties, the unreacted ClO2 gas must be contained and captured during fumigation events. Although activated carbon has been used during some decontamination events to capture the ClO2 gas, no data are available to quantify the performance of the activated carbon in terms of adsorption capacity and other sorbent property operational features. Laboratory experiments were conducted to determine and compare the ClO2 adsorption capacities of five different types of activated carbon as a function of the challenge ClO2 concentration. Tests were also conducted to investigate other sorbent properties, including screening tests to determine gaseous species desorbed from the saturated sorbent upon warming (to provide an indication of how immobile the ClO2 gas and related compounds are once captured on the sorbent). In the adsorption tests, ClO2 gas was measured continuously using a photometric-based instrument, and these measurements were verified with a noncontinuous method utilizing wet chemistry analysis. The results show that the simple activated carbons (not impregnated or containing other activated sorbent materials) were the most effective, with maximum adsorption capacities of approximately 110 mg/g. In the desorption tests, there was minimal release of ClO2 from all sorbents tested, but desorption levels of chlorine (Cl2) gas (detected as chloride) varied, with a maximum release of nearly 15% of the mass of ClO2 adsorbed.

Optimizing acidified bleach solutions to improve sporicidal efficacy on building materials

Aims:  We evaluated whether lowering pH (with acetic acid) and raising free available chlorine (FAC) levels in bleach solutions would improve efficacy in inactivating Bacillus spores on different materials. We also determined how varying pH and FAC levels affected bleach stability.

Capture of methyl bromide emissions with activated carbon following the fumigation of a small building contaminated with a Bacillus anthracis spore simulant

A wide-area Bacillus anthracis spore contamination incident will present immense challenges related to decontamination capacity. For this reason, fumigation with methyl bromide (MeBr) has been proposed as a potential remediation option. Although a few bench-scale laboratory studies have been conducted to evaluate activated carbon for the capture of MeBr, these studies were conducted at conditions replicating commodity fumigation using relatively low MeBr concentrations, temperatures, and/or relative humidity (RH) levels. The more rigorous MeBr fumigation requirements to fully inactivate B. anthracis spores are much more of a challenge for an activated carbon system (ACS) to capture MeBr, and warrant their own investigation. Further, while the aforementioned studies have shown activated carbon to be a possible option for the capture of MeBr in gas streams, these tests were conducted at laboratory bench scale, and thus lack operational perspective and data. Thus, we present for the first time the results of a full-scale study to evaluate an ACS employed for the capture of MeBr at conditions that would be used for decontaminating a building structure contaminated with B. anthracis spores. Airflow rate, temperature, RH, and MeBr levels were measured within the ACS during its operation. Despite the relatively high humidity, temperature, and MeBr levels, the MeBr capture efficiency of the ACS was demonstrated to be more than 99%. The concentration of MeBr exhausted from the structure was reduced from 41,000 to 136 ppmv in 3.5 hr, corresponding to an overall atmospheric emission rate of less than 2 kg. The practical adsorption rate of the ACS was determined to be 4.83 kg MeBr/100 kg carbon. The information and data presented here will facilitate future use of this technology when fumigating with MeBr. Implications: This investigation presents data to characterize the performance of a full-scale activated carbon system (ACS) for the capture of methyl bromide (MeBr) used for the decontamination (fumigation) of a small building contaminated with Bacillus anthracis spores. The data presented on the ACS operation and performance characteristics such as adsorption capacity, breakthrough times, and removal efficiency of MeBr will facilitate future use of this technology when fumigating with MeBr. Efficient capture of MeBr following fumigation (whether for anthrax inactivation or agricultural commodities) will reduce emissions to the atmosphere, thereby lowering potential human exposure as well as mitigating depletion of stratospheric ozone.