FIG 8.

Competitive index of the ΔtroR mutant against the WT strain (A) and CΔtroR complemented strain (B) in an intranasal mouse model. Groups of five BALB/c mice were intranasally infected with a 1:1 mixture of either the ΔtroR mutant and the WT strain (group 1) or the ΔtroR and CΔtroR strains (group 2). The blood, heart, liver, spleen, lung, kidney, and brain samples from the infected mice were collected at 12 h after infection. Bacteria recovered from the samples of mice in group 1 were analyzed by colony PCR to determine the competitive index (CI: the ratio of ΔtroR mutant to WT in each sample divided by that in the inoculum). Bacteria recovered from the samples of mice in group 2 were analyzed for spectinomycin susceptibility to determine the CI (the ratio of ΔtroR mutant to CΔtroR complemented strain in each sample divided by that in the inoculum). Mean CI values were compared to 1 (equal competitiveness) using the two-tailed paired t test to determine whether the difference in competitiveness was significant. As there were not enough bacterial cells recovered from the brain of one mouse in group 1, the data shown for this tissue are from four mice. As bacteria recovered from the lungs of two mice in group 2 were contaminated with other microbes, the data shown for this tissue are from three mice.