The study aimed to performed a deep phenotypic and genotypic analysis of fifteen clinical carbapenem-resistant strains isolated in Madagascar form 2008 to 2016.. Molecular characterization of carbapenem-resistant Acinetobacter baumannii strains isolated in Madagascar

Objectives: The present study aimed to perform a deep phenotypic and genotypic analysis of fifteen clinical carbapenem-resistant Acinetobacter baumannii (CRAb) strains isolated in Madagascar between 2008 and 2016 from diverse sources. Methods: Carbapenem-resistant isolates were subjected to susceptibility testing. A genetic analysis to assess the presence of antibiotic resistance determinants, insertion sequences, integrons, genomic islands and potential virulence factors was performed by whole genome sequencing for all strains. The presence of some efflux pumps and porin genes was also assessed in CRAb isolates.Results: All isolates were defined as multidrug-resistant (MDR) strains with high-level resistance to almost all antibiotics tested. Sequences analysis revealed several carbapenem resistance genes, namely blaOXA-51 like, blaOXA-23, blaOXA-24 and blaOXA-58 that were detected in 100%, 53.3%, 13.3% and 6.6% of the isolates, respectively. Additionally, an ISAba1 located upstream of blaOXA-23 and blaADC-like genes was observed in 53.3% and 66.7% of isolates respectively. Tn2006 and Tn2008 were found associated to the ISAba1-blaOXA-23 structure. Half of isolates (46.7%) were positives to class 1 integrons. CRAb isolates were distributed into five sequences types (STs) with predominantly the sequence-type ST2 followed by ST1.The vast majority of efflux and virulence genes screened were found in all CRAb isolates studied. Conclusions: This study revealed the presence of high-level of carbapenem resistance in A. baumannii with the first description of the OXA-24 and OXA-58 carbapenemases in Madagascar highlighting the importance to better monitor and control CRAb in Madagascan hospitals.