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.
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.
Authors: Anna L Sartor; Muhammad W Raza; Shahid A Abbasi; Kathryn M Day; John D Perry; David L Paterson; Hanna E Sidjabat Journal: Antimicrob Agents Chemother Date: 2014-06-30 Impact factor: 5.191