Global genomic survey of Salmonella Kentucky: discovery of a chromosomeborne blaNDM-5 and the emergence of ST314, an MDR clone mediated by the IncR plasmid.

Antimicrobial resistance (AMR) in Salmonella enterica serotype Kentucky (S. Kentucky) is a global challenge, with increasing resistance to cephalosporins, ciprofloxacin, and carbapenems significantly limiting treatment strategies, yet its worldwide dissemination patterns and AMR profiles remain unclear. Therefore, this study monitored the current trends in global spatiotemporal distribution and AMR of 9,557 S. Kentucky from 47 countries through large-scale genome-based molecular epidemiology. We revealed that S. Kentucky demonstrated a broad geographic distribution, with ST314 emerging as a novel epidemic sequence type, particularly in China. Additionally, we found chicken supply chain represents the main source for the transmission of S. Kentucky ST314 to humans. Particularly, ST314 represents an antimicrobial-resistant clone and exhibited resistance mechanisms distinct from the multidrug-resistant clone ST198. Notably, we made a groundbreaking discovery of the chromosome-borne blaNDM-5 in S. Kentucky, and the IncR plasmid was identified as a crucial mediator of AMR in Chinese ST314. Machine learning indicated that the IncR plasmid was involved in the localized evolution of ST314 within China. Based on the analyzed sequence data, we showed that ST314 was originated from the United Kingdom, and formed a unique antimicrobial-resistant clone specific to China with subsequent spread to other countries. Our analysis highlights the expanding geographic distribution and increasingly complex AMR of S. Kentucky, emphasizing the emergence of ST314 as a new global risk for the spread of antibiotic-resistant S. Kentucky.