Fig. 4.

Virulence potential of the Δcaf mutant of Y. pestis CO92 in both bubonic and pneumonic plague mouse models. The BALB/c mice were challenged subcutaneously (A and C) or intranasally (B) with the WT or Δcaf mutant of CO92 at the indicated doses. Mice were assessed for mortality during the duration of each experiment, and their percentages of survival were plotted. The Kaplan-Meier survival estimate was used to statistically analyze survival rates between WT- and Δcaf-infected mouse groups, and the corresponding P values are presented.