Characterization of Five Isolates Co-expressing ESBL and MCR-1 Resistance Mechanisms From Different Origins in China.

Present study characterized five co-expressing ESBL and MCR-1 recovered from food, food-producing animals, and companion animals in China. Antimicrobial susceptibility tests, conjugation experiments, and plasmid typing were performed. Whole genome sequencing (WGS) was undertaken for all five isolates using either PacBio RS II or Illumina HiSeq 2500 platforms. The cefotaxime and colistin resistance encoded by and genes, respectively, was transferable by conjugation either together or separately for all five strains. Interestingly, the ESBL and genes could be co-selected by cefotaxime, while the colistin only selected the -carrying plasmids during the conjugation experiments. Five sequence types (ST88, ST93, ST602, ST162, and ST457) were detected. Although diverse plasmid profiles were identified, IncI2, IncFIB, and IncFII plasmid types were predominant. These five clonally unrelated isolates harbored the gene located on similar plasmid backbones, which showed high nucleotide similarity to plasmid pHNSHP45. The gene can be co-transmitted with genes through IncI2 plasmids with or without IS in our study. Characterization of these co-existence ESBL and mcr-1 isolates extends our understanding on the dissemination of these resistance markers among bacteria of diverse origins.