title: Occurrence of blaNDM-7within IncX3-type plasmid of Escherichia coli from India.
abstract: 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-7and alteration in plasmid copy number under concentration gradient carbapenem stress.
  
  
  METHODS
  Six blaNDM-7producing 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-7was also determined. The change in copy number of transconjugable plasmid carrying blaNDM-7under exposure of different carbapenem antibiotics was determined by quantitative Real Time PCR.
  
  
  RESULTS
  All the six isolates carrying blaNDM-7were conjugatively transferable through an IncX3-type plasmid and were also found to co-harbor blaCTX-M-15. Genetic analysis of blaNDM-7showed an association of ISAba125, IS5 and a truncated portion of ISAba125 in the upstream region and bleMBLgene in the downstream region of blaNDM-7. Complete loss of the plasmids carrying blaNDM-7was observed between 85th to 90th serial passages when antibiotic pressure was withdrawn.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-7encoding plasmid was highly affected by the concentration of ertapenem.
  
  
  CONCLUSIONS
  The present study has first demonstrated presence of IncX3-type plasmid encoding blaNDM-7within nosocomial isolates of E. coli. Measures must be taken to prevent or atleast slowdown the emergence of this resistance determinant in this country.
authors.affiliation: Department of Microbiology, Assam University, Silchar, India.
authors.forename: Deepjyoti
authors.initials: D
authors.lastname: Paul
authors.affiliation: Department of Microbiology, Assam University, Silchar, India. Electronic address: ab0404@gmail.com.
authors.forename: Amitabha
authors.initials: A
authors.lastname: Bhattacharjee
authors.affiliation: Department of Microbiology, Assam University, Silchar, India.
authors.forename: Birson
authors.initials: B
authors.lastname: Ingti
authors.affiliation: Department of Microbiology, Assam University, Silchar, India.
authors.forename: Nargis Alom
authors.initials: NA
authors.lastname: Choudhury
authors.affiliation: Department of Microbiology, Assam University, Silchar, India.
authors.forename: Anand Prakash
authors.initials: AP
authors.lastname: Maurya
authors.affiliation: Department of Microbiology, Silchar Medical College and Hospital, Silchar, India.
authors.forename: Debadatta
authors.initials: D
authors.lastname: Dhar
authors.affiliation: Department of Microbiology, Silchar Medical College and Hospital, Silchar, India.
authors.forename: Atanu
authors.initials: A
authors.lastname: Chakravarty
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D015780:Carbapenems / Q000494:pharmacology; D003227:Conjugation, Genetic / Q000235:genetics; D000077727:Ertapenem; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D007194:India; D010957:Plasmids / Q000187:drug effects / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D015780:Carbapenems; D047090:beta-Lactams; D001618:beta-Lactamases; D000077727:Ertapenem
keywords: Carbapenemase; Escherichia coli; IncX3; bla(NDM-7)