FIG 6.

Induced expression of hilA increases epithelium disruption and secretion of proinflammatory cytokines by S. Paratyphi A. The integrity of the epithelial monolayer was determined for polarized Caco-2 cells infected at an MOI of 1:10 at 0, 3, 6, 8, 10, and 12 h p.i. and is shown as the change in transepithelial electrical resistance (TEER) from the time of infection (T0). S. Typhimurium SL1344 (A) and S. Paratyphi A 45157 (B) strains were grown under aerobic conditions to the late logarithmic phase in the presence of 100 μl/ml ampicillin and 50 mM arabinose. Data represent the means and SEM from three to five infections. An unpaired t test with two tails was used to determine the significance of the differences between S. Paratyphi A/pBAD18 and S. Paratyphi A/pBAD::hilA measurements. At 2 h p.i., supernatant was taken from the polarized Caco-2 cells and the concentration of secreted IL-8 (C) and Mip3α (D) was measured by ELISA. Data shown represent the means and standard deviations from three biological replicates. *, P < 0.05; **, P < 0.01; ***, P < 0.0001; ns, not significant.