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J Antimicrob Chemother. 2013 Aug;68(8):1737-40. doi: 10.1093/jac/dkt088. Epub 2013 Apr 3.

Detection of NDM-7 in Germany, a new variant of the New Delhi metallo-β-lactamase with increased carbapenemase activity.

Author information

1
Institute for Medical Microbiology and Infection Control, Hospital of Goethe-University, Frankfurt am Main, Germany. stephan.goettig@kgu.de

Abstract

OBJECTIVES:

This study characterized a new variant of the New Delhi metallo-β-lactamase (NDM).

METHODS:

A multidrug-resistant Escherichia coli isolate was recovered from the wounds, throat and rectum of a Yemeni patient who presented at the Frankfurt University Hospital in Germany. The presence of β-lactamase genes was analysed by PCR and sequencing. The isolate was further characterized by susceptibility testing, conjugation and transformation assays and plasmid analysis.

RESULTS:

The E. coli isolate was resistant to all β-lactams including carbapenems. By PCR analysis, the β-lactamase genes blaCMY-2, blaCTX-M-15, blaTEM-1 and blaNDM were identified. Sequencing revealed a blaNDM gene that differed from blaNDM-1 by two point mutations at positions 388 (G→A) and 460 (A→C) corresponding to amino acid substitutions Asp130Asn and Met154Leu, respectively. This NDM variant was identified as NDM-7. The blaNDM-7 gene was located on a self-transferable IncX3 plasmid of 60 kb. E. coli TOP10 transformants harbouring NDM-7 showed higher MICs of β-lactams including carbapenems compared with transformants harbouring NDM-1. Multilocus sequence typing analysis revealed that the E. coli isolate belonged to a novel sequence type (ST599).

CONCLUSIONS:

This study identified a novel NDM variant in E. coli, NDM-7, possessing a high ability to hydrolyse β-lactam antibiotics. Given the diversity of NDM variants located on self-transferable plasmids found in different Gram-negative species and isolated in different countries, the blaNDM gene will most likely efficiently disseminate worldwide.

KEYWORDS:

Enterobacteriaceae; IncX3; NDM-1; antibiotic resistance; carbapenems

PMID:
23557929
DOI:
10.1093/jac/dkt088
[Indexed for MEDLINE]

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