Characterization of a mouse model of plague after aerosolization of Yersinia pestis CO92

Yersinia pestis is a Gram-negative bacterium, and the causative agent of bubonic plague and pneumonic plague. Because of its potential use as a biological warfare weapon, the plague bacterium has been placed on the list of category A select agents. The dynamics of pneumonic infection following aerosolization of the highly virulent Y. pestis CO92 strain have been poorly studied; therefore, the purpose of this study was to determine the LD₅₀ dose, bacterial dissemination, cytokine/ chemokine production and tissue damage in Swiss-Webster mice over a 72 h course of infection. We exposed mice in a whole-body Madison chamber to various doses of Y. pestis CO92 aerosolized by a Collison nebulizer, and determined that the LD₅₀ presented dose (Dp) of the bacterium in the lungs was 2.1 × 10³ c.f.u. In a subsequent study, we infected mice at a Dp of 1.3 × 10⁴ c.f.u., and harvested organs and blood at 1, 24, 48 and 72 h post-infection. Histopathological examination, in addition to measurement of bacterial dissemination and cytokine/chemokine analysis, indicated progressive tissue injury, and an increased number of animals succumbing to infection over the course of the experiment. Using these data, we were able to characterize the mouse plague model following aerosolization of Y. pestis CO92.