-Lactamase OXA-143 in Acinetobacter baumannii

The carbapenem-hydrolyzing class D -lactamase OXA-253 was identified in an Acinetobacter baumannii clinical isolate be-longing to sequence type 113 (ST113) in Brazil. OXA-253 shares 93.8 % amino acid identity with OXA-143. The blaOXA-253 gene is located on a ca. 20-kb plasmid. The genetic environment of the blaOXA-253 gene shares the highest identity with ubiquitous GR2 group plasmids usually carrying blaOXA-24/-40 genes. Acinetobacter baumannii strains are frequently associated withnosocomial infections, and their resistance to carbapenems has risen in recent decades (1, 2). The main mechanisms of resis-tance to carbapenems of A. baumannii are efflux pumps, porin mutations, overexpression of the chromosomally encoded OXA-51-like -lactamase, and the biosynthesis of acquired carbap-enem-hydrolyzing class D -lactamases (CHDLs) (oxacillinases) (3). To date, fivemain groups of CHDLs have been identified inA. baumannii, the intrinsic chromosomally encoded OXA-51-like enzyme and the acquired chromosomally encoded and plasmid-encoded OXA-23-like, OXA-40-like, OXA-58-like, and OXA-143-like enzymes (3). OXA-143 was first described in 2009 fro