Prevalence and Genomic Characteristics of -Positive Escherichia coli Strains Isolated from Humans, Pigs, and Foods in China.

Colistin is one of the last-resort antibiotics for treating infections caused by multidrug-resistant (MDR) Gram-negative bacteria. However, genes conferring resistance to colistin have been widely identified, which is considered a global threat to public health. Here, we investigated the prevalence and characteristics of -harboring Escherichia coli strains isolated from humans, animals, and foods in China by PCR, antimicrobial susceptibility testing, conjugation experiments, molecular typing, genome sequencing, and bioinformatics analysis. In total, 135 -harboring E. coli isolates were acquired from 847 samples, and 6 isolates carried . Among them, 131 isolates were MDR bacteria. Sixty-five resistance genes conferring resistance to multiple antimicrobials were identified in 135 isolates. The diverse pulsed-field gel electrophoresis (PFGE) patterns and sequence types (STs) of -carrying isolates demonstrated that clonal dissemination was not the dominant mode of transmission. Seven types of plasmids were able to carry in this study, including IncI2, IncX4, IncHI2, p0111, IncY, and two hybrid plasmids. The genetic structures carrying of 60 isolates were successfully transferred into the recipient, including 25 IncI2 plasmids, 23 IncX4 plasmids, and an IncHI2 plasmid. was the dominant -bearing structure, followed by ISIS (Tn) and IS, among 7 -bearing structures of 135 isolates. In conclusion, IncI2, IncX4, and IncHI2 plasmids were the major vectors spreading from different geographical locations and sources. The prevalence of Tn may accelerate the transmission of . Continuous surveillance of and variants in bacteria is vital for evaluating the public health risk posed by genes. The spread of polymyxin-resistant Enterobacteriaceae poses a significant threat to public health and challenges the therapeutic options for treating infections on a global level. In this study, -bearing ST10 E. coli was isolated from pigs, pork, and humans simultaneously, which demonstrated that ST10 E. coli was an important vehicle for the spread of among animals, foods, and humans. The high prevalence of -positive E. coli strains in pigs and pork and the horizontal transmission of -bearing plasmids in diverse E. coli strains suggest that pigs and pork are important sources of -positive strains in humans and pose a potential threat to public health. Additional research on the prevalence and characteristics of -positive E. coli is still required to facilitate early warning to improve polymyxin management in hospitals.