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 beta-lactamase duplication in Acinetobacter genospecies 3 and of gene duplication mediated by ISAba125.