Regional dissemination of Acinetobacter species harbouring metallo-β-lactamase genes in Japan

Metallo-β-lactamase (MBL) producers have been reported among the various Acinetobacter species worldwide. In this study, the epidemiology and molecular characteristics of carbapenemase-encoding genes and mobile elements were studied to analyse the regional dissemination of MBL genes in Acinetobacter species. From January 2001 to December 2006, 48 Acinetobacter isolates harbouring MBL genes identified from five hospitals in Kyoto and Shiga Prefecture, Japan were collected and analysed. The partial rpoB gene or the 16S-23S ribosomal RNA intergenic spacer region was sequenced to obtain a species-level identification. Molecular typing using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) was performed. Twenty-five Acinetobacter pittii isolates were divided into eight PFGE types and five sequence types (STs) using MLST. Nine Acinetobacter bereziniae isolates belonged to five PFGE types. Five Acinetobacter nosocomialis isolates were divided into two PFGE types and two STs. Three unclassified Acinetobacter species isolates were divided into two PFGE types. Eighteen of the 25 A. pittii isolates belonged to ST119 and were identified from four hospitals. The blaIMP-19 gene was detected in 41 of 48 isolates, including all of the A. pittii ST119 isolates. The blaIMP-1 and blaIMP-11 genes were detected in four and three isolates, respectively. The MBL genes were all embedded within a class 1 integron as a gene cassette array: blaIMP-19-aac(6′)-31-blaOXA-21-aadA1, catB8-like/aacA4-blaIMP-1 and blaIMP-11. This study is the first report demonstrating the regional dissemination of MBL-producing Acinetobacter species. A. pittii ST119 harbouring blaIMP-19 was widely spread throughout the Kyoto-Shiga region.