The importance of this research was to determine the prevalence of efflux pump genes among Acinetobacter baumannii isolates from hospitalized patients in Imam Reza hospital in Tabriz, Iran. Materials and Methods: This descriptive study was conducted in the Imam Reza hospital, Tabriz, IR Iran during June 2013 to March 2014. Twenty-six strains were isolated from female patients (42.6%) and thirty-five from male patients (57.4%). Clinical specimens were cultured for isolation of the microbial

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... s of A. baumannii. The isolated bacteria were identified using biochemical tests. Disk diffusion susceptibility test was used to determine the antimicrobial susceptibility, and E-test methods were also used. The prevalence of efflux pump genes was detected by PCR and sequencing methods. Results: The resistance of A. baumannii isolates against tested antibiotics was analyzed as follows: 51 (84%) to trimethoprim-sulfamethoxazole, 59 (98%) to ceftazidime, 60 (99%) to ciprofloxacin, 29 (48%) to amikacin, 46 (77%) to gentamicin, 30 (50%) to tobramicin, , 60 (99%) to imipenem" 60 (99%) to meropenem" 60 (99%) to ceftriaxon" 60 (99%) to cefepime" 60 (99%) to ofloxacin, 6 (11%) to colistin. By using E-test, 45 (73.3%) to imipenem, 57 (93.3%) to ciprofloxacin, 23 (38%) to amikacin were also analyzed. The prevalence of adeA, adeB, adeC, and abeM genes was 54 (88.5%), 61 (100%), 57 (93.9%), and 60 (98.3%), respectively. Conclusion: The result of this study showed high incidence of AdeABC efflux pump in MDR A. baumannii isolates and the growing number of nosocomial infections associated with XDR A. baumannii complex, leading to difficulties in antibiotic therapy.