Consistency and Reproducibility of Bioaerosol Delivery for Infectivity Studies on Mice

Questions about the clinical significance of an antimicrobial resin use don personal respirators led system to generate consistent test bioaerosols for use in animal studies. The hypothesis was proposed that an aerosol delivery system based on the Collision nebulizer can be designed and engineered to provide, at selectable concentrations, a respiratory challenge of bioaerosol particles that is verifiably consistent in time and that can be fed in separate experiments through treated and untreated filters to deliver a consistent challenge to a small-animal model of human respiration. To verify this hypothesis, such an experimental filtration system was designed and built. Challenge trials were performed with MS2 bacteriophage and Bacillus atrophaeus. Over 30 to 40 minutes, the particle size distribution (PSD) was measured, and viability of microorganisms collected in All-Glass Impingers (AGI-4s) was determined. Concentrations of particles and microorganisms downstream of the filter were too low to measure, and the viable counts for MS2 bacteriophage were not measured at all owing to problems with the assay method. However, in each experiment, the coefficients of variations (CVs) of time-series measurements of the total particle count, count median diameter, and geometric experiments with viability data, all CVs of time-series measurements of upstream viable airborne concentration were less than 26%. This CV is somewhat higher than has been reported in the literature for tests with airborne Bacillus spores, but the plating method used to measure the viability may have introduced additional variation that was not caused within the system itself. It can be reasoned based on this data that the system can provide a sufficiently steady aerosol challenge to be used for later studies using a small-animal model of human respiration. The system provides a design for an animal exposure system incorporating aerosol filtration, which is a capability previously unreported. The original document contains color images. All DTIC reproductions will be in black and white.