Nowadays, due to the increasing resistance of Acinetobacter baumannii to antibiotics, it has been a problematic agent in clinical settings. As a significant nosocomial pathogen, A. baumannii isolates use resistant genes and biofilm development as means of survival. The aim of this study was to determine antimicrobial resistance patterns, aminoglycoside and carbapenems resistance genes, and biofilm formation among clinical isolates of A. baumannii. Materials and Methods: A cross-sectional study

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... as conducted from April 2018 to March 2019. In all, 133 nonduplicated isolates of A. baumannii were isolated from Yasuj and Bandar Abbas, located in Iran. Antimicrobial susceptibility was determined using disk diffusion. Carbapenem-and aminoglycoside-resistant genes were investigated by the polymerase chain reaction method. The ability to generate biofilms was evaluated using the microtiter plate method. Results: In this study, all isolates contained bla OXA-51-like and were confirmed as A. baumannii. High-level resistance was observed for carbapenems and aminoglycosides. The prevalence of oxacillinase genes blaOXA -23-like and bla OXA-24-like was 89 (66.9%) and 46 (34.6%), respectively. Moreover, the co-occurrence of bla-OXA-23-like and bla-OXA-24-like was 10 (7.5%). A total of 73 (54.9%) and 69 (51.9%) were positive for aac (3)-I and aph (3')-I, respectively. Furthermore, the coexistence of two genes was obtained in 55 (41.4%) isolates. The result demonstrates that 129 (97%) of isolated were strong, three (2.3%) moderate, and one (0.8%) weak biofilm producer. Conclusion: Results revealed that bla-OXA-23-like and aac (3)-I genes were the most prevalent resistance genes. Since a vast majority of isolates were drug-resistant with strong biofilms, infection control programs and policies should be frequently upgraded to control the transmission of drugresistant A. baumannii isolates in the future.