Molecular detection of AdeABC efflux pump genes in clinical isolates of Acinetobacter baumannii and their contribution in imipenem resistance

Backgrand: Multi-drug resistance due to Acinetobacter baumannii strains has become a significant challenge. Efflux pump plays a vital role in the development of resistance in this bacteria. The aim of this study was to evaluate the frequency of the AdeABC efflux pump genes and its role in resistance to imipenem in clinical isolates of A.baumannii. A total of 56 isolates of A.baumannii were collected from different clinical specimens of Valiasr hospital in the Arak –Iran and all isolates were identified by standard biochemical tests. The Antimicrobial susceptibility patterns were determined by disk diffusion method and minimum inhibitory concentrations of imipenemin via E-test strips with and without CCCP efflux pump inhibitor were determined according to CLSI guidelines. The PCR test was used to detect the AdeABC efflux pump genes in isolates. All A.bumannii isolates were resistant to cefotaxim, ceftazidim, cefepim, cefoxitin, azteronam, piperacillin-tazobactam and ciprofloxacin, as well as all isolates were resistant to imipenem according to the results of the E-test method. Imipenem MIC with efflux pump inhibitor not reduced in all isolates and showed no differences in imipenem activity. The adeA, adeB and adeC genes were found in 100%, 100% and 96.5% of isolates, respectively. AdeABC efflux system contributes to resistance to other antibiotics and resistance to imipenem has not been involved with this efflux system in A.baumanni isolates in current study and other mechanism such as carbapenemase enzymes play vital role to imipenem resistance in A.baumanni isolates.