Frequency of Resistance Phenotypes and Genotype of Acinetobacter Baumannii and Molecular Typing by PFGE in Patients Admit-ted to the Intensive Care Units of Zanjan Hospi-tals

Background: By acquiring resistance and through new mechanisms, Acinetobacter baumannii has turned into a global problem in nosocomial infections. The present study was conducted to determine the frequency of resistant strains and resistance genes and also molecular typing of hospital strains in the city of Zanjan.  Materials and Methods: A total of 250 clinical samples isolated from hospitalized patients in ICUs of Zanjan hospitals were cultured, and identified by the biochemical and blaOXA-51 gene tracking methods. The antibiotic susceptibility test was also run. The presence of integrons 1, 2 and 3, as well as oxacillinase genes was verified by PCR technique, and typing was carried out by the PFGE. The relationship of resistance genes with the antibiotic susceptibility pattern and clusters was determined. Results: Of the 250 samples, 68 isolates were identified as Acinetobacter, of which, 48 were Acinetobacter baumannii. 94% of the samples were identified as MDR strains, 46% as XDR strains, and 12% as PDR. The highest resistance of the 48 isolates of A. baumannii was attributed to ceftazidime, cefotaxime, and cotrimoxazole, and the highest susceptibility to Colistin (60%). The frequencies of resistance genes of integrons 1, 2, and 3 were 60%, 28%, and 0% respectively. The frequencies of carbapenem resistance genes for blaOXA-23, blaOXA-24, blaOXA-51, and blaOXA-58 were 74%, 24%, 100%, and 4%, respectively. The above samples were grouped into 26 palsutypes. Conclusion: In the study setting, resistance to Colistin showed an ascending trend, and high genetic diversity suggested diversity of A. baumannii strains.