BACKGROUND: New-Delhi metallo-β-lactamase-7 with higher hydrolytic activity than its ancestor NDM-1 is emerging across the globe including India. In this study, we have investigated the genetic context of blaNDM-7 and alteration in plasmid copy number under concentration gradient carbapenem stress. MATERIALS AND METHODS: Six blaNDM-7 producing Escherichia coli isolates were obtained from Silchar Medical College and Hospital and the co-existence of other β-lactamases and transferability of this resistant determinant was determined by transformation and conjugation assay followed by typing of the plasmid by PBRT method. Genetic context and plasmid stability of blaNDM-7 was also determined. The change in copy number of transconjugable plasmid carrying blaNDM-7 under exposure of different carbapenem antibiotics was determined by quantitative Real Time PCR. RESULTS: All the six isolates carrying blaNDM-7 were conjugatively transferable through an IncX3-type plasmid and were also found to co-harbor blaCTX-M-15. Genetic analysis of blaNDM-7 showed an association of ISAba125, IS5 and a truncated portion of ISAba125 in the upstream region and bleMBL gene in the downstream region of blaNDM-7. Complete loss of the plasmids carrying blaNDM-7 was observed between 85th to 90th serial passages when antibiotic pressure was withdrawn. After analyzing the relative copy number it was observed that the copy number of the blaNDM-7 encoding plasmid was highly affected by the concentration of ertapenem. CONCLUSION: The present study has first demonstrated presence of IncX3-type plasmid encoding blaNDM-7 within nosocomial isolates of E. coli. Measures must be taken to prevent or atleast slowdown the emergence of this resistance determinant in this country.
BACKGROUND: New-Delhi metallo-β-lactamase-7 with higher hydrolytic activity than its ancestor NDM-1 is emerging across the globe including India. In this study, we have investigated the genetic context of blaNDM-7 and alteration in plasmid copy number under concentration gradient carbapenem stress. MATERIALS AND METHODS: Six blaNDM-7 producing Escherichia coli isolates were obtained from Silchar Medical College and Hospital and the co-existence of other β-lactamases and transferability of this resistant determinant was determined by transformation and conjugation assay followed by typing of the plasmid by PBRT method. Genetic context and plasmid stability of blaNDM-7 was also determined. The change in copy number of transconjugable plasmid carrying blaNDM-7 under exposure of different carbapenem antibiotics was determined by quantitative Real Time PCR. RESULTS: All the six isolates carrying blaNDM-7 were conjugatively transferable through an IncX3-type plasmid and were also found to co-harbor blaCTX-M-15. Genetic analysis of blaNDM-7 showed an association of ISAba125, IS5 and a truncated portion of ISAba125 in the upstream region and bleMBL gene in the downstream region of blaNDM-7. Complete loss of the plasmids carrying blaNDM-7 was observed between 85th to 90th serial passages when antibiotic pressure was withdrawn. After analyzing the relative copy number it was observed that the copy number of the blaNDM-7 encoding plasmid was highly affected by the concentration of ertapenem. CONCLUSION: The present study has first demonstrated presence of IncX3-type plasmid encoding blaNDM-7 within nosocomial isolates of E. coli. Measures must be taken to prevent or atleast slowdown the emergence of this resistance determinant in this country.
Authors: Apostolos Liakopoulos; Jeanet van der Goot; Alex Bossers; Jonathan Betts; Michael S M Brouwer; Arie Kant; Hilde Smith; Daniela Ceccarelli; Dik Mevius Journal: Sci Rep Date: 2018-05-16 Impact factor: 4.379
Authors: Tim Flerlage; Jessica N Brazelton de Cardenas; Cherilyn D Garner; Nur A Hasan; Hiren Karathia; Amr Qudeimat; Gabriela Maron; Randall Hayden Journal: Open Forum Infect Dis Date: 2020-01-12 Impact factor: 3.835