Genetics and expression of the carbapenem-hydrolyzing oxacillinase gene blaOXA-23 in Acinetobacter baumannii

The genetic structures surrounding the plasmid-carried bla(OXA-23) oxacillinase gene, encoding resistance to carbapenems, were studied in Acinetobacter baumannii. ISAba1 and the novel element ISAba4 were detected upstream of the bla(OXA-23) gene, providing promoter sequences for its expression. These insertion elements were likely involved in transposition processes at the origin of acquisition of this beta-lactamase gene.