Sequence Analysis of ARI-1, a Novel OXA β-Lactamase, Responsible for Imipenem Resistance in Acinetobacter baumannii 6B92

The sequence of the blaARI-1 gene from imipenem-resistant Acinetobacter baumannii 6B92 has been determined. The structural gene encodes a 273-amino-acid protein which is most related to the OXA class D β-lactamases. The conserved S-T-F-K and K-T-G motifs were identified in the ARI-1 protein sequence, also named OXA-23, but significantly, a point mutation (Y→F) was identified in the Y-G-N conserved motif, also known to function in the active site.


Multiresistant Acinetobacter baumannii strains are now recognized as serious nosocomial pathogens (4, 5), and carbapenem-resistant strains are being reported increasingly (1, 3, 6, 11, 15, 18, 23). Imipenem-resistant A. baumannii 6B92 was isolated from a patient in Edinburgh, United Kingdom, in 1985 (15). Imipenem resistance was attributed to a novel serine β-lactamase, ARI-1 (15), and was subsequently demonstrated to be transferable to Acinetobacter junii (18). Imipenem resistance due to β-lactamases in A. baumannii has subsequently been reported worldwide, and two additional β-lactamases, ARI-2 (6) and an oxacillin-hydrolyzing enzyme (2, 11), defined only by their biochemical properties, have been described. In this paper we report the nucleotide and deduced amino acid sequences of ARI-1 carried by the R plasmid pUK1356.