Emergence of a bla _NDM-5 Carrying IncHI2/IncHI2A Plasmid in a Multidrug Resistant Clinical ST1431 Escherichia coli Strain

Carbapenems are the last-resort antibiotics used to treat infections caused by bacterial pathogens. Many bacterial pathogens have evolved to produce NDM carbapenemases to hydrolyze carbapenems, posing a great challenge to public health. In this study, we report a multidrug resistant clinical E. coli strain 673. Strain 673 belongs to sequence type (ST) 1431 and carries several plasmids, p673-blaTEM-1B, p673-blaCTX-M-55, p673-blaNDM-5, p673-13272, and p673-6468. p673-blaNDM-5 is an IncHI2/IncHI2A-type plasmid harboring several antibiotic resistance genes, including bla _NDM-5, strA, strB, and dfrA. The bla _NDM-5 gene was surrounded by two IS26 elements in p673-blaNDM-5, indicating that IS26 could mediate the integration of bla _NDM-5 into p673-blaNDM-5. p673-blaCTX-M-55 is an IncFII-type plasmid harboring fosA, aadA1, and bla _CTX-M-55. p673-blaTEM-1B is an IncFIB-type plasmid harboring bla _TEM-1B and dfrA5. p673-13272 is a ColRNAI-type plasmid that does not carry any drug resistance genes. This is the first report that a bla _NDM-5-bearing IncHI2/IncHI2A-type plasmid has emerged in a clinical E. coli strain in China. Our findings suggest that IS26 mediates the integration of bla _NDM-5 into p673-blaNDM-5. The spread of bla _NDM-5-bearing plasmids is a clinical challenge and endangers public health.