Genomic analysis of a multidrug-resistant monophasic Salmonella Typhimurium from Chinese beef harboring a novel mcr-1-bearing IncHI2-IncHI2A plasmid.

We conducted genomic analysis of a Chinese beef-derived, mcr-1-positive, multidrug-resistant monophasic Salmonella enterica serovar Typhimurium isolate. Antimicrobial resistance determinants were located on both its chromosome and plasmid. The multidrug resistance was primarily mediated by a novel IncHI2-IncHI2A plasmid harboring 18 resistance genes, including mcr-1, in contrast to only five resistance genes and one resistance-associated mutation detected on the chromosome. These findings underscore the need for enhanced surveillance of this pathogen.