Invasion of HCT-8 cells by Salmonella Typhimurium strains. (A) Time-points of 1 h and 4 h post-infection; (B) Time-points of 18 h, 24 h, and 48 h post-infection. The X-axis represents time (h) while the Y-axis represents average colony forming units (CFU) of bacteria per viable HCT-8 cell. The different Salmonella strains are color-coded according to the legend. Asterisk indicates significance of the mutant strain from the wild-type at p < 0.01 assessed at each time.