The prevalent dynamic and genetic characterization of mcr-1 encoding multidrug resistant Escherichia coli strains recovered from poultry in Hebei, China

•The genetic environment of mcr-1 showed its position on the p0111 plasmid in 2 isolates, a rarely reported plasmid type for the mcr-1 gene. Moreover, this type of plasmids was transferable in recipient J53, and mcr-1 was encoded by three mobile elements ISApl1, Tn3, and IS26, forming a novel backbone Tn3–IS26-mcr-1–pap2-ISApl1 on the p0111 plasmid.•Four O15: H10-serotype Escherichia coli (E. coli) carrying the mcr-1 gene have been identified in this study.•The mcr-1 gene can transfer horizontally with much stability in this study.•The mcr-1 gene from the present study has homology with mcr-1 E. coli from other sources, showing its clonal dissemination among the different hosts and species, which poses a potential threat to public health. Colistin is known as the last resort antibiotic to treat the infections caused by multidrug resistant foodborne pathogens. The emergence and widespread dissemination of plasmid-mediated colistin resistance gene mcr-1 in the Escherichia coli (E. coli) incurs potential threat to public health. Here, we investigated the epidemiology, transmission dynamics, and genetic characterization of mcr-1 harbouring E. coli isolates from poultry originated in Hebei Province, China. A total of 297 faecal samples were collected from the two large poultry farms in Hebei Province, China. The samples were processed for E. coli identification by matrix-assisted laser desorption ionization-time of flight mass spectrometry and 16S rDNA sequencing. Then, the mcr-1 gene harbouring E. coli strains were identified by polymerase chain reaction and subjected to antimicrobial susceptibility testing by broth microdilution assay. The genomic characterization of the isolates was done by whole genome sequencing using the various bioinformatics tools, and multi-locus sequence typing was done by sequence analysis of the seven housekeeping genes. The conjugation experiment was done to check the transferability of mcr-1 along with the plasmid stability testing. A total of six mcr-1 E. coli isolates with minimum inhibitory concentration of 4 μg/mL were identified from 297 samples (2.02%). The mcr-1 harbouring E. coli were identified as multidrug resistant and belonged to ST101 (n = 4) and ST410 (n = 2). The genetic environment of mcr-1 presented its position on IncHI2 plasmid in 4 isolates and p0111 in 2 isolates, which is a rarely reported plasmid type for mcr-1. Moreover, both type of plasmids was transferable to recipient J53, and mcr-1 was flanked by 3 mob