Identification of New Delhi metallo-β-lactamase gene (NDM-1) from a clinical isolate of Acinetobacter junii in China

New Delhi metallo-beta-lactamase-1 (NDM-1) is a novel type of metallo-b-lactamase (MBL) responsible for bacterial resistance to beta-lactam antibiotics. Acinetobacter junii was previously shown to possess a MBL phenotype; however, the genes responsible for this phenotype were not identified. In this study, we reported the identification of NDM-1 gene in a clinical isolate of A. junii from a child patient in China, which was resistant to all beta-lactams except aztreonam but sensitive to aminoglycosides and quinolones. The cloned NDM-1 gene contained an open reading frame of 813 bp and had a nucleotide sequence 99.9% identical (812/813) to reported NDM-1 genes carried by Acinetobacter baumannii, Enterococcus faecium, Escherichia coli, and Klebsiella pneumoniae. Recombinant NDM-1 protein was successfully expressed in E. coli BL21, and antibiotic sensitivities of the NDM-1-producing E. coli were largely similar to the A. junii 1454 isolate. The findings of this study raise attention to the emergence and spread of NDM-1-carrying bacteria in China.