Novel genetic context of multiple blaOXA-58 genes in Acinetobacter genospecies 3

Abstract

The detection in Acinetobacter genospecies 3 isolates of OXA-type carbapenemases, resulting in reduced susceptibility to carbapenem antibiotics, is increasingly reported. We identified an Acinetobacter genospecies 3 isolate carrying the gene for OXA-58 and aimed to resolve the genetic environment surrounding the bla_OXA-58 gene. Species identification was confirmed by 16S-23S rRNA restriction analysis. MICs of imipenem, meropenem and ertapenem were determined, and the isolate was screened by PCR for bla_OXA-23-like, bla_OXA-40-like, bla_OXA-51-like and bla_OXA-58-like genes. The sequence surrounding bla_OXA-58 was determined through amplification by inverse PCR and genome walking followed by sequencing. Genetic localization was investigated by Southern blotting. Isolate A164 was confirmed as belonging to Acinetobacter genospecies 3 and had reduced susceptibility to the carbapenems. The isolate was found to encode two bla_OXA-58 genes that may have been duplicated by the insertion sequence ISAba125, two copies of which were inserted into ISAba3 elements. The bla_OXA-58 genes appear to be plasmid borne. This is the first report of β-lactamase duplication in Acinetobacter genospecies 3 and of gene duplication mediated by ISAba125.