Multigeneration cross contamination of mail with Bacillus species spores by tumbling

Evaluation of standardized sample collection, packaging, and decontamination procedures to assess cross-contamination potential during Bacillus anthracis incident response operations

Sample collection procedures and primary receptacle (sample container and bag) decontamination methods should prevent contaminant transfer between contaminated and non-contaminated surfaces and areas during bio-incident operations. Cross-contamination of personnel, equipment, or sample containers may result in the exfiltration of biological agent from the exclusion (hot) zone and have unintended negative consequences on response resources, activities and outcomes. The current study was designed to: (1) evaluate currently recommended sample collection and packaging procedures to identify procedural steps that may increase the likelihood of spore exfiltration or contaminant transfer; (2) evaluate the efficacy of currently recommended primary receptacle decontamination procedures; and (3) evaluate the efficacy of outer packaging decontamination methods. Wet- and dry-deposited fluorescent tracer powder was used in contaminant transfer tests to qualitatively evaluate the currently-recommended sample collection procedures. Bacillus atrophaeus spores, a surrogate for Bacillus anthracis, were used to evaluate the efficacy of spray- and wipe-based decontamination procedures. Both decontamination procedures were quantitatively evaluated on three types of sample packaging materials (corrugated fiberboard, polystyrene foam, and polyethylene plastic), and two contamination mechanisms (wet or dry inoculums). Contaminant transfer results suggested that size-appropriate gloves should be worn by personnel, templates should not be taped to or removed from surfaces, and primary receptacles should be selected carefully. The decontamination tests indicated that wipe-based decontamination procedures may be more effective than spray-based procedures; efficacy was not influenced by material type but was affected by the inoculation method. Incomplete surface decontamination was observed in all tests with dry inoculums. This study provides a foundation for optimizing current B. anthracis response procedures to minimize contaminant exfiltration.

Multigeneration Cross-Contamination of Mail with Bacillus anthracis Spores

The release of biological agents, including those which could be used in biowarfare or bioterrorism in large urban areas, has been a concern for governments for nearly three decades. Previous incidents from Sverdlosk and the postal anthrax attack of 2001 have raised questions on the mechanism of spread of Bacillus anthracis spores as an aerosol or contaminant. Prior studies have demonstrated that Bacillus atrophaeus is easily transferred through simulated mail handing, but no reports have demonstrated this ability with Bacillus anthracis spores, which have morphological differences that may affect adhesion properties between spore and formite. In this study, equipment developed to simulate interactions across three generations of envelopes subjected to tumbling and mixing was used to evaluate the potential for cross-contamination of B. anthracis spores in simulated mail handling. In these experiments, we found that the potential for cross-contamination through letter tumbling from one generation to the next varied between generations while the presence of a fluidizer had no statistical impact on the transfer of material. Likewise, the presence or absence of a fluidizer had no statistically significant impact on cross-contamination levels or reaerosolization from letter opening.