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Abstract

Yersinia pestis (YP) causes plague, and its potential for aerosol dissemination and rapid disease progression are of particular concern for defence against bioterrorism. The high morbidity and mortality rates associated with plague and the recent emergence of multidrug resistance makes YP a potential threat to humans. Growth of YP at temperatures of the flea vector (28º C) and of the mammalian host are known to induce different proteins, contributing to different virulence. Here, a study comparing the disease progression of YP in a primary pneumonic mouse plague model following pre-incubation at 28º C and at 37º C was conducted. Mice were exposed to two inhalational (intranasal and aerosol) routes of infection and the LD50, bacterial dissemination, cytokine/chemokine production, and tissue damage at different time points over the course of infection were determined. Pre-incubation of YP strain NCTC144 at 37º C increased tissue dissemination and disease progression between 48 and 72h compared to at 28º C. In both intranasal and aerosol model of infection there was an increase in the severity of tissue injury that correlated with increased cytokine/chemokine expression at 37º C. In the intranasal route, there was a distinct difference in infection pattern between the two temperatures, with virulence higher at 37º C. This distinction was absent in the aerosol model. The present study correlates well with earlier reports of YP disease pattern in mice. Our study further confirms that the virulence and pathogenesis of YP are dependant on incubation conditions and route of infection

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