Genetic Diversity and Characteristics of bla NDM -Positive Plasmids in Escherichia coli .

New Delhi metallo-β-lactamases (NDMs), including at least 28 variants, are a rapidly emerging family of β-lactamases worldwide, with a variety of infections caused by NDM-positive strains usually associated with very poor prognosis and high mortality. NDMs are the most prevalent carbapenemases in Escherichia coli ( E. coli ) worldwide, especially in China. The vast majority of bla _NDM cases occur on plasmids, which play a vital role in the dissemination of bla _NDM . To systematically explore the relationships between plasmids and bla _NDM genes in E. coli and obtain an overall picture of the conjugative and mobilizable bla _NDM -positive plasmids, we analyzed the variants of bla _NDM , replicon types, phylogenetic patterns, conjugative transfer modules, host STs, and geographical distributions of 114 bla _NDM -positive plasmids, which were selected from 3786 plasmids from 1346 complete whole genomes of E. coli from the GenBank database. We also established links among the characteristics of bla _NDM -positive plasmids in E. coli . Eight variants of bla _NDM were found among the 114 bla _NDM -positive plasmids, with bla _{NDM - 5} (74 bla _{NDM - 5} genes in 73 plasmids), and bla _{NDM - 1} (31 bla _{NDM - 1} genes in 28 plasmids) being the most dominant. The variant bla _{NDM - 5} was mainly carried by the IncX3 plasmids and IncF plasmids in E. coli , the former were mainly geographically distributed in East Asia (especially in China) and the United States, and the latter were widely distributed worldwide. IncC plasmids were observed to be the predominant carriers of bla _{NDM - 1} genes in E. coli , which were mainly geographically distributed in the United States and China. Other bla _{NDM - 1} -carrying plasmids also included IncM2, IncN2, and IncHI1. Moreover, the overall picture of the conjugative and mobilizable bla _NDM -positive plasmids in E. coli was described in our study. Our findings enhance our understanding of the genetic diversity and characteristics of bla _NDM -positive plasmids in in E. coli .
Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
(Copyright © 2021 Zhang, Guo, Li, Li, Yang, Ni, Zhan, Lu, Zhang, Li and Zhou.)