Screening of New Delhi metallo-β-lactamase 1 for gram negative bacilli

Abstract

Objective To screen metallo-β-lactamase (MBL) and New Delhi metallo-β-lactamase 1 (NDM-1) genes among imipenem-resistant gram-negative bacilli,and to provide experimental evidence for the treatment and control of bacteria carrying NDM-1. Methods A total of 7 impenem-resistant gram-negative bacilli isolated from 7 patients in Guangzhou Women and Children′s Medical Center during 2010 were screened for NDM-1 gene retrospectively.The MBLs were examined by imipenemethylenediaminetetra acetic acid (EDTA) double-disc synergy test.NDM-1 gene-specific primers were designed for PCR amplification,and the PCR products were cloned into p MD-T plasmid and then transformed to E.coli Dh5a.Recombinant plasmid was identified by EcoRⅠ,XhoⅠ double enzyme and sequencing. Results Two MBL positive strains (Acinetobacter baumannii 1542,Acinetobacter junii 1454) were identified,and NDM-1 gene was verified in Acinetobacter junii 1454,and showed high concordance with known NDM-1 gene sequences in Genbank (99.9%).Only one nucleotide G-A mutation among 813 nucleotides (G468A) was found,and the amino acid sequences were exactly the same with known NDM-1.The accession number of the sequence of Acinetobacter junii NDM-1 under Genbank is HQ603057.Acinetobacter junii 1454 was resistant to all beta-lactams antibiotics tested except aztreonam and cefoperazone/sulbactam but sensitive to tigecycline,aminoglycosides and quinolones. Conclusion NDM-1 positive Acinetobacter junii was screened from a hospitalized child,suggesting that clinical microbiology laboratories should strengthen imipenem-resistant NDM-1 gene screening.(Chin J Lab Med,2013,36:916-919) Key words: Gram-negative bacteria; beta-Lactamases; Imipenem; Drug resistance; bacterial