Figure 2.

Attenuated virulence of the KIM/D27 Y. pestis pnp deletion mutant in a murine model of infection. Groups of 10 adult, female Swiss Webster mice were infected with a range of infectious doses (10⁵–10⁸) of either Y. pestis KIM/D27 parental (Lindler et al., 1990) or a derived pnp‐deleted mutant (Rosenzweig et al., 2005) strain via the IP route. Additionally, the complemented (compl) pnp mutant strain, in which the pKAK 7‐ plasmid encoded pnp gene was provided in trans, was used at an infectious dose of 1.0 × 10⁸. Per cent survival post infection was monitored and is graphically represented. Yersinia pestis strains were grown overnight in heart infusion broth (Gibco) and the appropriate dilutions were made to achieve the desired infectious dose. Mice were observed up to a period of 35 days post infection. Asterisks represent statistical significance (P < 0.05) as determined by the Kaplan–Meier's survival estimates.