FIG. 1.

Kinetics of colonization of the respiratory tract of C57BL/6 mice by the RB50 and LPaV strains. Mice were intranasally inoculated with 5 × 10⁵ CFU of either the RB50 or LPaV strain in 25-μl droplets. At the indicated time points postinoculation, mice were sacrificed, and the bacterial burdens in the nasal septum, trachea, and lungs were enumerated. Each symbol indicates the results for a single mouse. The dashed line indicates the limit of detection. The bars indicate standard deviations. A statistical analysis was carried out using an unpaired two-tailed Student t test to compare the numbers of CFU obtained from the groups of RB50-infected mice to the numbers of CFU obtained from mice inoculated with the LPaV strain. The asterisks indicate P values (one asterisk, P ≤ 0.05; two asterisks, P ≤ 0.005; three asterisks, P ≤ 0.0005).