A Novel Insertion Sequence, IS <i>Aba10</i> , Inserted into IS <i>Aba1</i> Adjacent to the <i>bla</i> _OXA-23 Gene and Disrupting the Outer Membrane Protein Gene <i>carO</i> in <i>Acinetobacter baumannii</i>

Abstract

We investigated an outbreak caused by carbapenem-resistant Acinetobacter baumannii carrying the bla(OXA-23) gene. A novel insertion sequence (IS), named ISAba10, was found to be inserted into the ISAba1 element preceding the bla(OXA-23) gene in a group of isolates showing higher carbapenem MICs. The presence of ISAba10 was associated with increased OXA-23 expression, likely by providing additional promoter sequences. ISAba10 was also inserted into the carO outer membrane protein gene in most of these isolates.