FIG. 6.

The Δppk1 mutant is defective for long-term intracellular survival in an epithelial cell model of infection. Wild-type (WT), Δppk1, and ppk1* strains were grown to mid-log phase in MH broth. At the zero time point, semiconfluent or confluent monolayers of INT407 cells were inoculated with bacteria at MOIs of ∼100 (A) and ∼20 (B). After 3 h, the cells were washed, and gentamicin was added at 150 μg/ml to all wells for 2 h to kill extracellular bacteria. Gentamicin was washed from the cells at 5 h, and invaded intracellular bacteria were harvested and plated for enumeration (inv). To all remaining wells, fresh media containing 10 μg of gentamicin/ml and 3% fetal bovine serum were added. After an additional 2 h (2h IC) or 18 or 19 h (18h or 19h IC) of incubation, cells were washed, and surviving intracellular bacteria were harvested. For all time points, experiments were performed in triplicate, and error bars are shown.