Standard method for deposition of dry, aerosolized, silica-coated Bacillus spores onto inanimate surfaces
D Harnish1, B K Heimbuch, M McDonald
1Engineering Science Division, Applied Research Associates, Panama City, FL, USA.
Aims:
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 × 10(5) CFU cm(-2) ; coefficient of variation (CV) was <40% for 96% of samples. Laboratory B produced a mean loading concentration of 7·82 × 10(6) CFU cm(-2) ; 68% of samples demonstrated CV <40%.
Conclusions:
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.
