Exou Contributes to Late Killing of Pseudomonas Aeruginosa - Infected Endothelial Cells

To ascertain the role of ExoU in late P. aeruginosa cytotoxicity, endothelial cells (EC) were exposed to wild type PA103, PA103∆exoU and PA103::exsA for 1h and to gentamicin in culture medium. After 24h, the viability of PA103-infected cells (33.7 ± 14.3%) was significantly lower than the viability of PA103∆exoU(77.7 ± 6.3%) or PA103::exsA(79.5 ± 23.3%) infected EC. P. aeruginosa cytotoxicity did not depend on the bacterial ability to interact with EC because the percentage of cells with associated PA103 (35.9 ± 15.8%) was similar to the percentage in PA103∆exoU(34.2 ± 16.0%) and lower than the percentage in PA103::exsA-infected cultures (82.9 ± 18.9%). Cell treatment with cytochalasin D reduced the PA103 internalization by EC but did not interfere with its ability to kill host cells.