K. pneumoniae ompA mutants induce higher levels of IL-8 than wild-type strains by airway epithelial cells. A, ELISA of IL-8 released by A549 cells left untreated (CON) or infected for different time points with Kp52145 (gray bars) and 52OmpA2 (black bars) (n = 3). B, ELISA of IL-8 released by A549 cells left untreated (CON) or infected for 8 h with different K. pneumoniae strains (n = 3). C, ELISA of IL-8 released by A549 cells left untreated (CON) or infected for different time points with 52OmpA2 (gray bars) and 52145-ΔwcaK2ompA (black bars) (n = 3). D, ELISA of IL-8 released by NHBE cells left untreated (CON) or infected for 8 h with different K. pneumoniae strains (n = 3). E, adhesion (left) and internalization (right) of Klebsiella strains to A549 cells (n = 3). Gray bars, CPS-expressing strains; black bars, CPS negative strains. The data (A–E) are means and S.E. (error bars). A–D, *, p < 0.05 (for the indicated comparisons; one-way ANOVA). E, *, p < 0.05 (results are significantly different from the results for Kp52145; one-tailed t test).