FIG. 4.

Survival of Shigella-infected macrophages. Cells of macrophage cell line J774 were infected with wild-type and plasmid-cured Shigella flexneri strain CCUG 29416 grown in the presence of the compounds. The fluorescence intensity was measured in a microplate reader (Calcein, 485/535 nm; Sytox Orange, 535/595 nm), and the relative amounts of living cells and cells with the cell membrane destroyed, respectively, were calculated. The bars show the mean values from three samples, and the standard deviations were calculated according to a Gauss formula suitable for percentage values. Cells infected by wild-type Shigella without addition showed a value of around 40% living cells. The value for uninfected cells was set to 100% living cells.