Carbapenem resistance in Acinetobacter baumannii clinical isolates from northwest Iran: high prevalence of OXA genes in sync.

Abstract

Background and Objectives:Carbapenem treatment for Acinetobacter baumannii infections presently faces threats owing to the production of several types of carbapenemase enzymes, prevalence of which varies among different countries. We explored the current trend of antibiotic resistance in A. baumannii clinical isolates from North West Iran, sought the mechanism of carbapenem resistance and addressed the sequence type groups in carbapenem resistant A. baumannii (CRAB).Materials and Methods:A. baumannii (n=112) isolates were recovered from various clinical specimens of patients admitted in internal, surgery, burn, infectious diseases and various ICUs wards. Genetically confirmed A. baumannii isolates were screened for carbapenem resistance by the Kirby-Bauer and E-test and the presence of bla MBL, bla OXA-like, ISAba1 genes by PCR. Sequence groups were identified by multiplex PCR.Results:Multidrug-resistance (MDR) was a characteristic feature of all A. baumannii isolates. Frequency of oxacillinase genes in combination including bla OXA-51-like/bla OXA-23-like, bla OXA-51-like/blaOXA-24/40-likeand bla OXA-51-like/bla OXA-23-like/bla OXA-24/40-like was 82.1%, 36.6% and 25.8% respectively. Blending of oxacillinase and MBL genes was evident in eight bla OXA-23-like positive and 7 bla OXA-24-like positive isolates thereby depicting synchronous etiology of carbapenem resistance. Amongst CRAB isolates, 97.3% contained ISAba1 element and 50.9% belonged to the European clone II.Conclusion:Synchronicity among bla OXA-like with bla MBL and ISAba1 gene was a hallmark of this investigation. Though origin or route of transmission was not elucidated in this study but co-existence among OXA and MBL producing genes is a therapeutic concern demanding strict surveillance strategies and control programs to halt the dissemination of these isolates in the hospital setting.