OXA-58, a Novel Class D β-Lactamase Involved in Resistance to Carbapenems in Acinetobacter baumannii

Abstract

ABSTRACT A carbapenem-resistant Acinetobacter baumannii strain was isolated in Toulouse, France, in 2003. Cloning and expression in Escherichia coli identified the carbapenem-hydrolyzing β-lactamase OXA-58, which is weakly related (less than 50% amino acid identity) to other oxacillinases. It hydrolyzed penicillins, oxacillin, and imipenem but not expanded-spectrum cephalosporins. The bla OXA-58 gene was located on a ca. 30-kb non-self-transferable plasmid. After electrotransformation in the A. baumannii CIP7010 T reference strain, it conferred reduced susceptibility to carbapenems. The bla OXA-58 gene was bracketed by two novel IS Aba3- like insertion elements. This study describes a newly characterized β-lactamase that may contribute to carbapenem resistance in A. baumannii .