FIG. 1.

Bacteria that do not express a translocation-competent T3SS fail to elicit rapid neutrophil recruitment to the lung. C57BL/6 mice were infected intranasally with 5 × 10⁴ CFU of PA103, ΔUT, pcrV::Tn5, or pscJ::Tn5 bacteria and then sacrificed at 4 h.p.i. (A) Bacterial recovery from lung tissue expressed as the ratio of output (CFU per lung) over input (inoculum per mouse); bars indicate geometric means. Bacterial recovery did not differ significantly between groups (P = 0.4, Kruskal-Wallis test). (B to D) Total cells (B), neutrophils (C), and macrophages (D) recovered from BAL fluid; lines indicate median values. Each point represents the value for an individual animal. Significantly more total cells and neutrophils were recovered from BAL fluid from PA103 and ΔUT strain-infected animals than from pcrV or pscJ strain-infected animals (P < 0.001, Kruskal-Wallis test followed by Dunn's posttest comparison). (E) Percentages of neutrophils and macrophages in BAL fluid samples; error bars indicate means ± standard errors of the means. ***, P < 0.001 for Dunn's multiple-comparison posttest. Data shown are from 3 independent experiments with 4 to 6 mice per group.