Clonal relation between Salmonella enterica subspecies enterica serovar Dublin strains of bovine and food origin in Germany

Salmonella enterica subspecies enterica serovar Dublin (S. Dublin) is a host-adapted serovar causing enteritis and/or systemic diseases in cattle. As the serovar is not host-restricted, it may cause infections in other animals, including humans with severe illness and higher mortality rates than other non-typhoidal serovars. As human infections are mainly caused by contaminated milk, milk products and beef, information on the genetic relationship of S. Dublin strains from cattle and food should be evaluated to gain a better understanding on the possible zoonotic potential of the cattle adapted serovar S. Dublin.
Whole genome sequencing (WGS) of 144 S. Dublin strains from cattle and 30 strains from food origin was performed. Multilocus sequence typing (MLST) revealed mostly sequence type ST-10 from both, cattle and food isolates. 14 out of 30 strains from food origin were clonally related to at least one strain from cattle, as detected by core-genome Single-Nucleotide Polymorphisms Typing as well as core-genome MLST. The remaining 16 food-borne strains fit into the genome structure of S. Dublin in Germany without outliers. WGS proved to be a powerful tool to gain information on the epidemiology of Salmonella strains but also to detect clonal relations between organisms isolated from different stages of production. This study has shown a high correlation between S. Dublin strains from cattle and food and, therefore, the zoonotic potential of the bovine adapted serovar. S. Dublin strains of both origins share an almost identical set of virulence factors emphasizing their potential to cause severe clinical manifestations in animals but also in humans and thus the need for effective control S. Dublin in a farm to fork strategy.