Decontamination efficacy of three commercial-off-the-shelf (COTS) sporicidal disinfectants on medium-sized panels contaminated with surrogate spores of Bacillus anthracis.

In the event of a wide area release and contamination of a biological agent in an outdoor environment and to building exteriors, decontamination is likely to consume the Nation's remediation capacity, requiring years to cleanup, and leading to incalculable economic losses. This is in part due to scant body of efficacy data on surface areas larger than those studied in a typical laboratory (5×10-cm), resulting in low confidence for operational considerations in sampling and quantitative measurements of prospective technologies recruited in effective cleanup and restoration response. In addition to well-documented fumigation-based cleanup efforts, agencies responsible for mitigation of contaminated sites are exploring alternative methods for decontamination including combinations of disposal of contaminated items, source reduction by vacuuming, mechanical scrubbing, and low-technology alternatives such as pH-adjusted bleach pressure wash. If proven effective, a pressure wash-based removal of Bacillus anthracis spores from building surfaces with readily available equipment will significantly increase the readiness of Federal agencies to meet the daunting challenge of restoration and cleanup effort following a wide-area biological release. In this inter-agency study, the efficacy of commercial-of-the-shelf sporicidal disinfectants applied using backpack sprayers was evaluated in decontamination of spores on the surfaces of medium-sized (∼1.2 m2) panels of steel, pressure-treated (PT) lumber, and brick veneer. Of the three disinfectants, pH-amended bleach, Peridox, and CASCAD evaluated; CASCAD was found to be the most effective in decontamination of spores from all three panel surface types.

Detection and tracking of a novel genetically tagged biological simulant in the environment.

A variant of Bacillus thuringiensis subsp. kurstaki containing a single, stable copy of a uniquely amplifiable DNA oligomer integrated into the genome for tracking the fate of biological agents in the environment was developed. The use of genetically tagged spores overcomes the ambiguity of discerning the test material from pre-existing environmental microflora or from previously released background material. In this study, we demonstrate the utility of the genetically "barcoded" simulant in a controlled indoor setting and in an outdoor release. In an ambient breeze tunnel test, spores deposited on tiles were reaerosolized and detected by real-time PCR at distances of 30 m from the point of deposition. Real-time PCR signals were inversely correlated with distance from the seeded tiles. An outdoor release of powdered spore simulant at Aberdeen Proving Ground, Edgewood, MD, was monitored from a distance by a light detection and ranging (LIDAR) laser. Over a 2-week period, an array of air sampling units collected samples were analyzed for the presence of viable spores and using barcode-specific real-time PCR assays. Barcoded B. thuringiensis subsp. kurstaki spores were unambiguously identified on the day of the release, and viable material was recovered in a pattern consistent with the cloud track predicted by prevailing winds and by data tracks provided by the LIDAR system. Finally, the real-time PCR assays successfully differentiated barcoded B. thuringiensis subsp. kurstaki spores from wild-type spores under field conditions.

Efficient methods for large-area surface sampling of sites contaminated with pathogenic microorganisms and other hazardous agents: current state, needs, and perspectives.

The recovery operations following the 2001 attacks with Bacillus anthracis spores were complicated due to the unprecedented need for large-area surface sampling and decontamination protocols. Since this event, multiple reports have been published describing recovery efficiencies of several surface sampling materials. These materials include fibrous swabs of various compositions, cloth wipes, vacuum socks, and adhesive tapes. These materials have reported recovery efficiencies ranging from approximately 20% to 90% due to the many variations in their respective studies including sampling material, composition of surface sampled, concentration of contaminant, and even the method of deposition and sample processing. Additionally, the term recovery efficiency is crudely defined and could be better constructed to incorporate variations in contaminated surface composition and end user needs. While significant efforts in devising protocols for large-area surface sampling have been undertaken in the years since the anthrax attacks, there is still a general lack of consensus in optimal sampling materials and the methodology in which they are evaluated. Fortunately, sampling efforts are continuing to be supported, and the knowledge gaps in our procedures, methodology, and general understanding of sampling mechanisms are being investigated which will leave us better prepared for the future.

Surface sampling of spores in dry-deposition aerosols.

The ability to reliably and reproducibly sample surfaces contaminated with a biological agent is a critical step in measuring the extent of contamination and determining if decontamination steps have been successful. The recovery operations following the 2001 attacks with Bacillus anthracis spores were complicated by the fact that no standard sample collection format or decontamination procedures were established. Recovery efficiencies traditionally have been calculated based upon biological agents which were applied to test surfaces in a liquid format and then allowed to dry prior to sampling tests, which may not be best suited for a real-world event with aerosolized biological agents. In order to ascertain if differences existed between air-dried liquid deposition and biological spores which were allowed to settle on a surface in a dried format, a study was undertaken to determine if differences existed in surface sampling recovery efficiencies for four representative surfaces. Studies were then undertaken to compare sampling efficiencies between liquid spore deposition and aerosolized spores which were allowed to gradually settle under gravity on four different test coupon types. Tests with both types of deposition compared efficiencies of four unique swabbing materials applied to four surfaces with various surface properties. Our studies demonstrate that recovery of liquid-deposited spores differs significantly from recovery of dry aerosol-deposited spores in most instances. Whether the recovery of liquid-deposited spores is overexaggerated or underrepresented with respect to that of aerosol-deposited spores depends upon the surface material being tested.