Fig. 3

Mouse intranasal challenge model results. We compared the survival rates of 30 (3 × 10) mice exposed to the ΔFTT0482c, ΔFTT1538c, and ΔFTT1597 mutants for intranasal doses of ≥78 CFUs, with 10 mice exposed to wild-type strain doses of 320 CFU. Animals were monitored for 21 days. All mice exposed to the high-dose of the wild-type strain died by the end of the fifth day (blue line), whereas mice exposed to mutant strains had a slower time to death and survived in larger numbers 21 days post-exposure (purple, red, and orange lines). There was a statistically significant difference in the survival rate of mice exposed to mutant strains and mice exposed to the wild-type strain (p-value ≤10^-3). These results support the notion that each of the three mutants attenuates virulence when infected in mice via the intranasal route of infection