Co-occurrence of blaNDM-1 with blaOXA-23 or blaOXA-58 in clinical multidrug-resistant Acinetobacter baumannii isolates in Algeria

The aim of this study was to characterise the mechanisms of carbapenem resistance in Acinetobacter baumannii strains isolated in an Algerian hospital. A total of 43 imipenem-resistant A. baumannii clinical isolates collected between 2010 and 2013 were identified using API 20NE and were confirmed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Antibiotic susceptibility testing was performed by the disk diffusion and Etest methods. Carbapenemase activity was detected using microbiological tests and PCR. Genetic transfer of the bla(NDM-1) gene was performed by conjugation using sodium azide-resistant Escherichia coli J53 as recipient strain. Clonal relationships were studied by multilocus sequence typing (MLST) using partial sequences of the csuE and bla(OXA-51) genes. All 43 A. baumannii isolates were resistant to imipenem with high minimum inhibitory concentrations (MICs) (> 32 mu g/mL). The strains harboured bla(OXA-23), bla(NDM-1), bla(OXA-58) and/or bla(OXA-24) genes. Co-existence of bla(NDM-1) and bla(OXA-23) or bla(OXA-58) was detected in two isolates and one isolate, respectively. NDM-1 plasmid transfer to E. coli J53 was successful only for one of the three strains harbouring both bla(NDM-1) and bla(OXA-23) or bla(OXA-58). The phylogenetic tree obtained from concatenation of the partial sequences of csuE and bla(OXA-51) showed that there was no genetic relationship between the isolates and the bla(NDM-1) resistance gene. Here we report for the first time the co-occurrence of bla(NDM-1) along with bla(OXA-23) or bla(OXA-58) in recent clinical isolates of A. baumannii from Northeast Algeria. These findings re-emphasise the dissemination and rapid spread of blaNDM-1 carbapenemase genes in multidrug-resistant clinical A. baumannii isolates in Algeria. (C) 2016 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.