Epidemiological characteristics and genetic structure of blaNDM-1 in non-baumannii Acinetobacter spp. in China

Abstract

Objectives: The goal of this study was to investigate the epidemiological characteristics and the surrounding genetic structure of blaNDM-1 in non-baumannii Acinetobacter spp. in China. Methods: Non-baumannii Acinetobacter spp. were collected from 28 provinces in China and were screened for the presence of blaNDM-1 using PCR. The following four methods were used to classify the Acinetobacter isolates: the Vitek 2 system, 16S-23S rRNA gene intergenic spacer sequencing, amplified rDNA restriction analysis and partial rpoB sequence analysis. An S1-PFGE assay and Southern blot hybridization were performed to determine the plasmid location of blaNDM-1. The transferability of blaNDM-1-harbouring plasmids was confirmed by conjugation experiments and electrotransformation. The surrounding genetic structure of the blaNDM-1 gene was analysed using a restriction endonuclease-based cloning approach and primer walking. Results: Among 726 non-baumannii Acinetobacter spp., nine isolates collected from six different provinces and assigned to seven different Acinetobacter spp. contained the blaNDM-1 gene. None of these isolates was directly infectious to the patients or demonstrated an epidemiological importation from abroad. These blaNDM-1 genes were located on plasmids that could be transferred to Escherichia coli J53 by conjugation and Acinetobacter baylyi ADP1 by electrotransformation. Seven of the nine strains shared a common genetic structure in which blaNDM-1 was flanked by two copies of ISAba125. Conclusions: The clinical challenge posed by blaNDM-1 is currently minimal in China; however, more attention should be devoted to monitoring the dissemination of this gene due to its potential transferability via the ISAba125-associated transposon. © The Author 2012. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.