Molecular characterization of carbapenem-non-susceptible Acinetobacter spp. in Japan: predominance of multidrug-resistant Acinetobacter baumannii clonal complex 92 and IMP-type metallo-β-lactamase-producing non-baumannii Acinetobacter species.

We conducted an epidemiological study concerning carbapenem-non-susceptible clinical isolates of Acinetobacter spp. in Japan by molecular procedures including carbapenemase gene identification and amplified ribosomal DNA restriction analysis. Among 598 clinically isolated Acinetobacter spp. in 2007, 27 (4.5%) were non-susceptible to carbapenems. Most carbapenem-non-susceptible Acinetobacter baumannii (13/14) belonged to clonal complex (CC) 92, harbored bla (OXA-51-like) genes, including novel bla (OXA-206), downstream of ISAba1, and were recovered mainly from the Kanto region. Carbapenem-non-susceptible A. baumannii CC92 isolates were further divided by pulsed-field gel electrophoresis into two groups, one of which was characterized by the presence of bla (OXA-23). One A. baumannii CC276 isolate carried bla (IMP-1) and bla (OXA-58). Almost all non-baumannii Acinetobacter isolates (12/13), including Acinetobacter pittii (formerly Acinetobacter genomic species 3) and Acinetobacter nosocomialis (formerly Acinetobacter genomic species 13TU), produced IMP-type metallo-β-lactamases, and were recovered from various regions in Japan. This is the first report describing the nationwide molecular epidemiology of carbapenem-non-susceptible Acinetobacter spp. with genomic species-level identification in Japan.