Characterization of a Novel -Bearing Plasmid in ST395 of Chicken Origin.

The emergence of mobile colistin resistance genes undermines the efficacy of colistin as the last-resort drug for multi-drug resistance infections and constitutes a great public health concern. Plasmids play a critical role in the transmission of genes among bacteria. One colistin-resistant strain of chicken origin was collected and analyzed by antimicrobial susceptibility testing, PCR, conjugation assay and S1-PFGE. Whole-genome sequencing (WGS) approach combining Illumina and MinION platforms was utilized to decipher the underlying colistin resistance mechanism and genetic context. A novel -bearing plasmid p2019036D-mcr8-345kb with 345 655 bp in size encoding various resistance genes including , , (D), and was identified responsible for the colistin resistance phenotype. Plasmid comparison has shown that the -bearing plasmid differed from other reported plasmids positive for but shared the same core -bearing conserved region. This study demonstrates the emergence of -bearing of animal origin is a potential risk to humans.