Characterization of the Naturally Occurring Oxacillinase ofAcinetobacter baumannii

Abstract

A chromosomally encoded oxacillinase, OXA-69, was characterized from Acinetobacter baumannii AYE. β-Lactamase OXA-69 shared 97% amino acid identity with the recently described OXA-51 enzyme of A. baumannii and 62 and 56% amino acid identity with the carbapenem-hydrolyzing oxacillinases OXA-24 and OXA-23, respectively. Biochemical characterization of the purified OXA-69 revealed a narrow-spectrum hydrolysis profile but including, at a low level, imipenem and meropenem. By PCR and sequencing bla_OXA-69-like genes were identified in all A. baumannii strains tested (n = 12), suggesting that this oxacillinase is naturally occurring in that species.