FIGURE 3.

Intracellular survival of S. Typhimurium strains in D. discoideum. Individual infection assays were conducted to evaluate the intracellular survival of different S. Typhimurium strains in D. discoideum AX4. (A) Relative intracellular survival at different times post infection. All values were calculated as CFU_{t =x}/CFU_{t =0} and further normalized to the value of the wild-type strain at t = 1. (B) Variation in the population of viable amoeba during the infection assay. All values were calculated as cells/mL and further normalized to the value of amoeba infected with the wild-type strain at t = 0. Graphs show mean values ± SD from at least 7 independent assays. Statistical significance of differences in intracellular survival between each strain and the wild type at a given time was determined using a one-way ANOVA with Dunnett’s test (^∗P < 0.05; ^∗∗P < 0.01; ^∗∗∗P < 0.001). Statistical significance of differences in intracellular survival of a given strain at t = 1 versus t = 24 was determined using a one-way ANOVA with Dunnett’s test (^#P < 0.05; ^###P < 0.001).