Identification of a novel NDM variant, NDM-13, from a multidrug-resistant Escherichia coli clinical isolate in Nepal

Abstract

A novel New Delhi metallo-β-lactamase, NDM-13, was identified in a carbapenem-resistant Escherichia coli clinical isolate obtained from the urine of a patient in Nepal. The enzymatic activity of NDM-13 against β-lactams was similar to that of NDM-1. However, NDM-13 displayed significantly higher k cat/Km ratios for cefotaxime. The genetic environment of bla NDM-13 was determined to be tnpA-IS30-bla NDM-13-ble MBL-trpF-dsbC-cutA-groES-groL, with bla NDM-13 located within the chromosome.

FIG 1

Localization of the bla_NDM-13 gene on the chromosome of E. coli strain IOMTU558, separated by pulsed-field gel electrophoresis (PFGE). Lanes: A, contour-clamped homogeneous electric field (CHEF) DNA size marker (Saccharomyces cerevisiae; Bio-Rad, Hercules, CA); B, I-CeuI-digested total DNA of E. coli IOMTU558; C, lambda ladder pulsed-field gradient (PFG) marker (New England BioLabs, Ipswich, MA); D, hybridization of I-Ceu-I-digested total DNA of IOMTU558 with a 16S rRNA-specific probe; and E, hybridization of I-Ceu-I-digested total DNA of IOMTU558 using a bla_NDM-13-specific probe.