OXA (beta)-lactamases in Acinetobacter: the story so far.

The emergence of carbapenem resistance in Acinetobacter baumannii has become a global concern since these beta-lactams are often the only effective treatment left against many multiresistant strains. A recent development has been the discovery of a novel group of narrow-spectrum OXA beta-lactamases in carbapenem-resistant strains, some of which have acquired the ability to hydrolyse the carbapenems. The first of these was found in a strain isolated in Edinburgh before imipenem was in use in the hospital. Whether these carbapenemases have been acquired or are part of the genetic make-up of this species has yet to be determined. More importantly, however, they represent an important stage in the evolution of antibiotic resistance in Acinetobacter. This paper discusses the emergence of these unusual enzymes over the past decade.