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Standard method for deposition of dry, aerosolized, silica-coated Bacillus spores onto inanimate surfaces




To evaluate a standard aerosolization method for uniformly depositing threat-representative spores onto surfaces.

Methods and Results

Lyophilized Bacillus anthracis ΔSterne spores, coated in silica, were aerosolized into a containment chamber and deposited onto nine surface types by two independent laboratories. Laboratory A produced a mean loading concentration of 1·78 × 105 CFU cm−2; coefficient of variation (CV) was <40% for 96% of samples. Laboratory B produced a mean loading concentration of 7·82 × 106 CFU cm−2; 68% of samples demonstrated CV <40%.


This method has been shown to meet the goal of loading threat-representative spores onto surfaces with low variability at concentrations relevant to the Department of Defense.

Significance and Impact of the Study

As demonstrated in 2001, a biological attack using anthrax disseminated as a dry powder is a credible threat. This method will provide a means to load spores onto surfaces that mimic a ‘real-world’ scenario of an aerosolized anthrax attack. The method has utility for evaluating sporicidal technologies and for nondecontamination studies, for example fate and transport or reaerosolization.

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