Population genomics of emerging multidrug-resistant Salmonella derby from pork and human in Guangdong, China

Salmonella is a foodborne pathogen that poses a severe public health threat. Salmonella enterica serovar Derby (S. S. Derby) is one of the top five serovars isolated from humans and animals, and it carries the potential risk of transmission to humans through consumption of pork and related products. This study isolated 98 S. Derby, mainly from pork, and clinical samples in Guangdong to investigate and compare their molecular characteristics, phylogenetic relationships, transmission routes, antimicrobial resistance phenotypes, genotypes, and virulence profiles. Whole-genome sequencing (WGS) revealed that all S. Derby isolates belonged to ST40 and displayed a relatively large core genome. Phylogenomic analysis indicated the possibility of clonal transmission of S. Derby not only between pork and humans but also across geographic areas in Guangdong over an extended period of time. Discriminant analysis of principal components (DAPC) model showed that a significant proportion of S. Derby isolates retrieved from multiple hosts originated from pork. Furthermore, similar antimicrobial resistance phenotypes and genotypes were found in S. Derby strains recovered from animal products and humans. All S. Derby isolates were found to contain numerous virulence genes, primarily related to fimbrial adherence determinants and secretion system components. This study offers valuable insights into the transmission routes of S. Derby between pork and humans and provides essential data for public health management.