Mobile Colistin Resistance Gene - Detected on an IncI2 Plasmid in Typhimurium Sequence Type 19 from a Healthy Pig in South Korea.

Colistin is considered the last resort for the treatment of multi-drug resistant Gram-negative bacterial infections. We studied colistin resistance and the gene carriage in isolates recovered from food animals in South Korea between 2010 and 2018. Colistin resistance was found in 277 isolates, predominantly in Enteritidis (57.1%) and Gallinarum (41.9%). However, the gene was identified in only one colistin-resistant Typhimurium (MIC = 16 µg/mL) isolated from a healthy pig. The carrying isolate presented additional resistance to multiple antimicrobials. The strain belonged to sequence type (ST)19 and carried various virulence factor genes that are associated with adhesion and invasion of into intestinal epithelial cells, as well as its survival in macrophages. The gene was identified on an IncI2 plasmid and it was also transferred to the . J53 recipient strain. The --carrying plasmid (pK18JST013) in this study was closely related to that previously reported in . Indiana (pCFSA664-3) from chicken in China. This is the first report of carrying . Typhimurium in South Korea. The finding indicates the importance of regular screening for the presence of the - gene in . Typhimurium in food animals to prevent the spread to humans.