Emergence of mcr-1 and mcr-3 variants coding for plasmid-mediated colistin resistance in Escherichia coli isolates from food- producing animals in South Korea.

We hereby report the first characterization of mcr-3 gene from healthy animals in South Korea. Out of 636 E. coli isolates, collected between 2014- 2017, nine colistin resistant isolates were screened for the presence of mcr-1 and mcr-3 genes. Nine (1.4%) isolates had shown resistance for colistin and among them three and two isolates were mcr-1 harboring and mcr-3 harboring strains, respectively. All the colistin-resistant isolates were multidrug-resistant. mcr-1 and mcr-3 genes were confirmed to be transferred to a recipient E. coli J53 AZR.