FIG. 3.

Colonization by and dissemination of ΔpsaA, Δcaf1, and ΔpsaA Δcaf1 mutant Y. pestis strains in C57BL/6J mice during pneumonic plague. Mice were infected i.n. with ∼10⁴ CFU of the wild-type (diamonds) or ΔpsaA (triangles), Δcaf1 (squares), or ΔpsaA Δcaf1 (circles) mutant strain. Mice were sacrificed at 12, 48, and 60 h postinfection, and colonization of the lungs (A) and spleen (B) was determined. Each symbol represents an individual animal. Black bars correspond to the median number of CFU/g of tissue for each group. The dashed line indicates the limit of detection. Asterisks in the table indicate a significant difference between the median number of CFU/g of tissue compared to either the wild-type or the ΔpsaA Δcaf1 mutant strain (*, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.005; na, not applicable; ns, not significant). The data are a combination of three independent experiments. The numbers of tissue samples harvested for the wild-type and ΔpsaA, Δcaf1, and ΔpsaA Δcaf1 mutant strains, respectively, were 9, 4, 10, and 10 at 12 h; 19, 11, 19, and 19 at 48 h; and 9, 12, 12, and 11 at 60 h.