Determination of antibiotic resistance pattern and prevalence of OXA-type carbapenemases among Acinetobacter baumannii clinical isolates from inpatients in Isfahan, central Iran

Abstract

Acinetobacter baumannii is one of the most important bacterial species with the ability to produce OXA-type carbapenemases. We aimed to evaluate the prevalence of OXA-type carbapenemases among clinical isolates of A. baumannii in three major hospitals of Isfahan. In this cross-sectional descriptive study, 153 non-repeated strains of A. baumannii were isolated from various clinical samples of hospitalized patients in Al-Zahra, Imam Mousa Kazem, and Shariati hospitals from October 2015 to October 2016. Antimicrobial susceptibility testing for imipenem, meropenem, ertapenem, cefepime, ceftazidime, ceftriaxone, piperacillin-tazobactam, gentamicin, amikacin, ciprofloxacin, and tetracycline was performed using the disk diffusion method. In order to identify bla-oxa genes, a multiplex polymerase chain reaction was used. The resistance rates in A. baumannii isolates to beta-lactam antibiotics including imipenem, ertapenem, meropenem, cefepime, ceftazidime, ceftriaxone, and piperacillin/tazobactam were 100, 100, 99.3, 97.4, 96.7, 97.4, and 98.6, respectively. PCR assay showed the presence of bla-oxa genes in all isolates. The bla-oxa-51 gene was recognized in all (100) isolates, 90.8 and 62.1 of isolates possessed the bla-oxa-23 and bla-oxa-24 genes, respectively, while the bla-oxa-58 gene was not detected in any of the isolates. Also, 56.2 of isolates had both the bla-oxa-23 and bla-oxa-24 genes simultaneously. We found that the prevalence of OXA-type carbapenemases among carbapenem-resistant A. baumannii isolates is high in Isfahan, with OXA-23 being the major carbapenemase mechanism responsible for the resistance phenotype.