The characteristics of mcr -bearing plasmids in clinical Salmonella enterica in Sichuan, China, 2014 to 2017.

is one of the most important zoonotic pathogens and a major cause of foodborne illnesses, posing a serious global public health hazard. The emergence of plasmid-mediated genes in has greatly reduced the clinical choice of salmonellosis treatment. The aim of this study was to investigate the plasmid characteristics of -positive Salmonella identified from patients in Sichuan, China during 2014 to 2017 by whole genomes sequencing. In this study, a total of 12 -positive isolates (1.15%, ; -1, n=10; -3, n=2) were identified from 1046 Salmonella isolates using PCR. Further characterization of these isolates was performed through antimicrobial susceptibility testing, conjugation assays, whole genome sequencing, and bioinformatics analysis. The gene in these isolates were carried by three types of typical -bearing plasmids widely distributed in Enterobacteriaceae (IncX4, IncI2 and IncHI2). Of note, two mcr-1-harboring IncHI2 plasmids were integrated into chromosomes by insertion sequences. Two -bearing plasmids were IncC and IncFIB broad-host-range plasmids respectively. Genetic context analysis found that was mainly located in Tn or truncated Tn, and shared a common genetic structure . Overall, we found that gene in clinical were commonly carried by broad-host plasmids and have potential to transfer into other bacteria by these plasmids. Continuous surveillance of MDR in humans and investigation the underlying transmission mechanisms of ARGs are vital to curb the current severe AMR concern.