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Antimicrobial agents and chemotherapy. 2008;52(9):2999- 3005. https://doi.org/10.1128/AAC.01684-07 PMid:185912 75 PMCid:PMC25335092230-8407https://doi.org/10.7897/2230-8407.097133https://t.ly/7OMn2MSA Google ScholarThis study aimed to investigate the virulence (adhesion and invasion) of clinically isolated multidrug resistant (MDR) A. baumannii on different mammalian cell lines. It also determined the role of the outer membrane protein (OmpA) extracted from such isolates in cytotoxicity to these cell lines. In this study, hundred thirty- seven clinical isolates were obtained from intensive care units (ICUs) at tertiary hospitals in Cairo, Egypt and were identified by API system. Identification was confirmed by polymerase chain reaction (PCR) amplification of the oxa-51 gene. Based on their susceptibility to different antimicrobial agents, tested by disc diffusion method, isolates were classified into different groups. Representative isolates of each group were assayed for adherence and invasion on HEp-2, A549 and Hela cells. OmpA was then extracted from selected strains. The cytotoxicity and caspase activation of the extracted OmpA was determined on different cell lines. The isolates were found to harbor the oxa-51 gene. Multidrug resistance was accompanied by higher binding capabilities on HEp-2 and A549 cells than Hela cells. A relation between cytotoxicity and Caspase activation was suspected among the isolates. These results suggested that apoptosis induced by OmpA of MDR A. baumannii might be attributed to caspase activation, though other mechanism could not be ruled out. In conclusion, A. baumannii has the ability to cause adhesion and invasion on respiratory cell other than other types of cells. OmpA has a vital role in the pathogenesis as it causes apoptosis to the respiratory cells.enUniversity of Adhesion, Invasion, A. baumannii, OmpA, cytotoxicity, caspaseArticlehttps://doi.org/10.7897/2230-8407.097133