High prevalence of OXA-type carbapenemases among Acinetobacter baumannii strains in a teaching hospital of Tehran.

Nosocomial infection caused by carbapenem-resistant Acinetobacter baumannii (CRAB) has created a public health concern all around the world. In this study, 100 isolates of CRAB from hospitalized patients during 2015-2016 at Imam Khomeini Hospital were investigated to determine the rates of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains using Kirby-Bauer disk diffusion method. The minimum inhibitory concentrations (MICs) of six antibiotics were determined by broth microdilution method. Multiplex polymerase chain reaction (PCR) was performed to detect blaOXA-51 like and blaOXA-58 like , blaOXA-23 like , and blaOXA-24 like that are encoding resistance to carbapenems. All CRAB isolates were MDR and XDR and 2% of them were pandrug-resistant (PDR), whereas colistin, polymyxin B, and tigecycline were the most effective agents. All isolates were positive for blaOXA-51 like by PCR. The frequency of blaOXA-23 like and blaOXA-24 like was 81% and 22%, respectively. Findings of this study showed that very few therapeutic options remained for the treatment of CRAB infections and blaOXA-23 like is a dominant resistance gene in CRAB at this hospital.