Determining the Antibiotic Resistance Pattern and the Frequency of the Most Common Resistance Genes in Acinetobacter baumannii Complex Isolates from Two Medical Centers in Tehran

Background:Acinetobacter baumannii is a major cause of nosocomial infections.Today, the increasing trend of antibiotic resistance in this bacterium has created many therapeutic challenges.This study aimed to assess the antibiotic resistance pattern and the presence of the most important resistance genes in A. baumannii complex clinical isolates collected from two medical centers in Tehran.Materials & Methods: In this study, 73 clinical isolates of A. baumanii complex belong to patients hospitalized in Sina and Shariati hospitals in 2018 were obtained from the university's microbial collection.Standard biochemical tests and PCR (polymerase chain reaction) detection of the 16srRNA gene were performed to confirm A. baumannii complex isolates.Antibiotic sensitivity test was done using disk diffusion method.Isolates with resistance to three or more antibiotic classes were defined as multidrug-resistant (MDR).The frequency of genes encoding aminoglycoside-modifying enzymes and those responsible for resistance to beta-lactam antibiotics was determined using PCR method.Findings: A total of 73 isolates were confirmed as A. baumannii complex.The isolates showed the highest resistance (100%) to ciprofloxacin, cefotaxime, and ceftazidime They also showed high resistance to other antibiotics.Ninety-three percent of the isolates were classified as MDR.Genetic analysis confirmed the presence of bla OXA-2 , aphA6, and bla VIM genes in 100% of A. baumannii complex isolates.Furthermore, the isolates contained ant (87.67%), bla IMP (65.75%), aacC1 (76.71%), aadA1 (35.61%), and aadB (61.64%) genes. Conclusion:The prevalence of antibiotic-resistant A. baumannii complex strains has increased among hospitalized patients, leading to significant therapeutic challenges.