Investigation of oxacillinases type beta-lactamases in carbapenems resistant Acinetobacter baumannii clinical isolates

Abstract

Acinetobacter baumannii, one of the most important infectious agents spread in hospitals, is an opportunistic, Gram-negative, aerobic and nonfermentative pathogen causing outbreaks often in ICUs and difficulties in treatments due to multiple antibiotic resistance characteristics. Carbapenem resistance in A. baumannii is a growing public health concern and most often mediated by oxacillinases carbapenemases. Carbapenems are significant representatives of the group β-lactamases that are used in the treatment of A. baumannii. OXA-23, OXA-24, OXA-51 and OXA-58 are the most common type of OXA gene family members which are responsible for carbapenem resistance. This study aimed to identify the carbapenem resistant A. baumannii isolates in ICU and analyse OXA-23, OXA-24, OXA-51 and OXA-58 genes’ expressions by using reverse transcritptase-PCR. In this study, A. baumannii isolates collected from the respiratory tract samples obtained from the patients receiving treatment between June 2017 and January 2018 at the ICU in Amasya University Sabuncuoğlu Serefeddin Education and Research Hospital. Collected samples identified by VITEK-2 device. Resistance profiles of carbapenem-resistant strains against to cefepime, ceftazidime, ciprofloxacin, levofloxacin, amikacin, gentamicin, tetracycline, tigecycline and colistin antibiotics were determined by disk diffusion and minimum inhibition concentration tests. Moreover, OXA-23, OXA-24, OXA-51 and OXA-58 genes were investigated by reverse transcritptase-PCR. Identified 50 A. baumannii isolates were found to be 100% resistant to imipenem, meropenem, cefepime, ceftazidime and ciprofloxacin, 94% for levofloxacin, 68% for amikacin, 78% for gentamicin, 88% for tetracycline and 6% for tigecycline. It was detected that all samples are susceptible to colistin and showed multiple antibiotic resistance. As a result of molecular analyses, it was also determined that the expressions of only OXA-23 and OXA-51 genes in all isolates. This study is one of the first reports to analyse A. baumannii isolated from respiratory tract samples in terms of microbiological and molecular analyses.