FIG. 5.

Invasion kinetics of L. monocytogenes EGD-e, ΔfliF, and ΔfliI strains in two different cell types: Caco-2 cells (A) and bone marrow-derived macrophages (B). Bacteria grown overnight at 30°C (or 37°C) were used to infect cell monolayers (100 bacteria per cell for Caco-2 cells; 0.1 bacteria per cell for macrophages). The temperatures given in the figure are the temperatures of bacterial growth before infection. All the infections were carried out at 37°C. After 30 min of infection, cells were washed and reincubated in fresh medium containing gentamicin in order to kill extracellular bacteria. After incubation (time given in abscissa) following washing, cells were lysed, and viable bacteria were counted on BHI agar plates. Values and error bars represent the means and standard deviations of the numbers of bacteria per well (three wells per assay and two different assays).