FIG. 1.

Colonization and dissemination of ΔpsaA, Δcaf1, and ΔpsaA Δcaf1 mutant Y. pestis strains in C57BL/6J mice during bubonic plague. Mice were infected s.c. in the neck with ∼10² CFU of the wild-type (wt, diamonds) or ΔpsaA (triangles), Δcaf1 (squares), or ΔpsaA Δcaf1 (circles) mutant strain. Mice were sacrificed at 36, 48, and 72 h postinfection, and colonization of the superficial cervical lymph nodes (A), spleen (B), and lungs (C) 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 graph indicate a significant difference between the median number of CFU/g of tissue between the ΔpsaA and Δcaf1 groups, whereas 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 represent three independent experiments. The numbers of tissue samples harvested for the wild-type and ΔpsaA, Δcaf1, and ΔpsaA Δcaf1 mutant strains, respectively, were 20, 7, 14, and 14 at 36 h; 21, 7, 14, and 14 at 48 h; and 19, 7, 14, and 14 at 72 h.