THE INVESTIGATION OF OXACILLINASE / METALLO-BETA-LACTAMASE GENES AND CLONAL ANALYSIS IN CARBAPENEM RESISTANT ACINETOBACTER BAUMANNII

Abstract

Introduction: Acinetobacter baumannii isolates cause multidrug resistant infections and serious nosocomial outbreaks. The increase in resistance to a variety of antibiotics and carbapenems globally forms a serious clinical problem. In our study, we aimed to investigate the presence of oxacillinase and metallo-beta-lactamase genes responsible for resistance in carbapenem resistant A. baumannii isolates isolated in our hospital and to reveal the clonal relationship between these isolates.

Materials and methods: A. baumannii isolates of identification was completed using traditional methods and a fully automatic identification kit. Carbapenem-resistant isolates were evaluated using the minimal inhibition concentrations (MIC) E-test method. Oxacillinase and metallo-beta-lactamase genes were researched using polymerase chain reaction (PCR). Pulsed-field gel electrophoresis (PFGE) experiment was completed to determine the clonal relationship of carbapenem-resistant isolates.

Results: When the antibiotic susceptibility of A. baumannii isolates are assessed, the most effective antibiotic for all isolates was found to be colistin with 97.1% susceptibility rate. All carbapenem resistant isolates were found positive for OXA-51, with 97% positive for OXA-23, and 5.7% positive for OXA-24. One isolates was found to have the VIM resistant gene. None of the isolates were found to have OXA-58, OXA-48, IPM, SPM, SIM, GIM and NDM-1 genes. In the clonal distribution of isolates 3 different pulsotypes were determined. Of these 38 were a, 11 were b and 3 were c pulsotypes. The majority of isolates (73%) were shown to belong to a single clone and this was assessed as the outbreak isolate.

Conclusion: In our study, colistin was the most effective antibiotic against A. baumannii. OXA-23 was the most common carbapenemase among A. baumannii isolates in our hospital. Carbapenem-resistant A. baumannii strains producing OXA-23 have the potential for outbreak. Monitoring of resistance mechanisms is important to identify appropriate treatment approaches and to prevent the spread of resistant strains.