Occurrence of blaNDM-7 within IncX3-type plasmid of Escherichia coli from India

Publication date: Available online 26 January 2017
Source:Journal of Infection and Chemotherapy
Author(s): Deepjyoti Paul, Amitabha Bhattacharjee, Birson Ingti, Nargis Alom Choudhury, Anand Prakash Maurya, Debadatta Dhar, Atanu Chakravarty
BackgroundNew-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 methodsSix 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.ResultsAll 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loss of the plasmids carrying blaNDM-7 was observed between 85th to 90th serial passages when antibiotic pressure was withdrawn.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.ConclusionThe 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.



from #AlexandrosSfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/2j8c98k
via IFTTT