Diverse flanking sequence types of blaNDM in IncX3 and IncB/O/K/Z plasmids in Escherichia coli isolated from poultry

We identified 33 bla NDM-harboring Escherichia coli in 470 poultry samples from Shandong and Guangdong provinces during 2016 to 2017 and included the subtypes bla NDM-1, bla NDM-5 and bla NDM-9. The bla NDM gene possessed by all strains was plasmid-borne and ranged in size from 46 to 265 kb. The plasmids included the replicon types IncX3, IncY, IncB/O/K/Z and IncHI2 and most were transferable and stable in recipient host bacteria. Sequences flanking bla NDM in IncX3 and IncB/O/K/Z plasmids were diverse and the mobile element IS 26 played an important role in the evolution of the IncB/O/K/Z bla NDM plasmids.