WVDL Collaboration Leads to Additional Findings on Heidelberg - Wisconsin Veterinary Diagnostic Laboratory

WVDL Collaborates with Others to Publish ‘Genome Divergence and Increase Virulence of Outbreak Associated Salmonella enterica subspecies enterica serovar Heidelberg’ in Gut Pathogens

The WVDL continues to see multi-drug resistant (MDR) Salmonella enterica subspecies enterica serotype/serovar Heidelberg infections in dairy beef calves and more recently beef steers and cows. To better understand this Salmonella isolate, the WVDL collaborated with researchers at South Dakota State University (SDSU) and the SDSU Veterinary Diagnostic Laboratory. Whole genome based single nucleotide polymorphism based analysis of the isolates from the 2015 and 2016 multi-state outbreak of Salmonella ser. Heidelberg which also had human cases confirmed in fifteen different states were analyzed. It is believed the majority of human cases were caused by direct contact with dairy beef calves that were sick with active Salmonella ser. Heidelberg infection. Traditionally, Salmonella ser. Heidelberg was predominately a Salmonella serovar adapted to poultry. This publication defines the relatedness of the Salmonella ser. Heidelberg strains collected from many different hosts and also examined both virulence and antibiotic resistance genes. The 2015-2016 outbreak isolates did cluster together and were highly related. As compared to older Salmonella ser. Heidelberg isolates, the outbreak-associated strain had more antibiotic resistance genes and contained Salmonella atypical fimbriae (Saf) genes that were absent in other Salmonella ser. Heidelberg strains, which may have contributed to the increased disease severity of these strains in both humans and calves.