Characteristics of colistin-resistant Escherichia coli from pig farms in Central China

Abstract The emergence and dissemination of colistin resistance in Enterobacteriaceae mediated by plasmid-borne mcr genes recent years now pose a threat to public health. In this study, we isolated characterized colistin-resistant and/or -positive E. coli from pig farms Central China. Between 2018 2019, 594 samples were collected recovered 445 isolates. Among them, 33 with phenotypes 37 that positive for identified, including 34 mcr-1 , one mcr-3 two both . An insertion nine bases (“CTGGATACG”) into four isolates led gene dysfunction, therefore did not confer the phenotype. Antimicrobial susceptibility testing revealed showed severe drug profiles, as 50% them resistant 20 types antibiotics. Multilocus sequence typing heterogeneous group isolates, among which ST10 (5/37), ST156 ST617 (4/37) predominant types. Plasmid conjugation assays -carrying plasmids 25 conjugated recipient, frequencies ranging 1.7 × 10 -6 4.1 -3 per recipient. Conjugation these conferred phenotype upon recipient bacterium. PCR harbored transconjugants determined six plasmid replicons, IncX4 (14/25), FrepB (4/25), IncI2 (3/25), IncHI2 (2/25), FIB (1/25), IncI1 (1/25). This study contributes current understanding antibiotic molecular characteristics farms.