Antimicrobial resistance of Indiana from retail chickens in China and emergence of an -harboring isolate with concurrent resistance to ciprofloxacin, cefotaxime, and colistin.

serotype Indiana ( Indiana) in Chinese poultry meat has aroused widespread concern because of its high prevalence and strong antimicrobial resistance. In consideration of the relationship in our previous study between Indiana and co-resistance to ciprofloxacin and cefotaxime (CIP-CTX), which were the first-line drug which were used in infection in clinical, the antimicrobial resistance (AMR) of 224 CIP-CTX co-resistant Indiana isolated from retail chicken samples in China were investigated, with the aim of characterizing the AMR profiles and related resistance mechanisms to ciprofloxacin and cefotaxime among these CIP-CTX co-resistant Indiana isolates, all of which showed multi-drug-resistant (MDR) phenotypes. GyrA (S83F and D87N/G) with ParC (T57S and S80R) were the dominant amino acid substitution types, with , and identified as common plasmid-mediated quinolone resistance (PMQR)-encoding genes. Five gene subtypes were identified with ranking at the top. Equally important, we obtained one isolate CFSA664 harboring the gene was ESBL producer with co-resistance to nine in ten classes of tested drugs inclduing colistin. A single circular chromosome and 3 circular plasmids were found in its genome. Among the 26 AMR genes identified, 24 were located on plasmid pCFSA664-1, including three ESBL genes, while plasmid pCFSA664-3 owning only the gene and sharing the same backbone structure with plasmids from Enterobacteriaceae. No insertion sequences were found near the gene but a relaxase-encoding gene in the flank, which could transfer into J53 at a relatively high frequency. Indiana in this study exhibited highly drug-resistant phenotypes, contributing to the acceleration of the dissemination and emergence of this pathogen among different sources. Surveillance and a One Health strategy are needed to limit the emergence of Indiana along the food chain.