The University of Georgia College of Veterinary Medicine

Georgia Veterinary Scholars Program

GVSP Summer 2006 Scholars

Georgia Veterinary Scholar	Faculty Mentor

Will Greggs Tuskegee University Class of 2008	Dr. John Maurer

Are Certain Salmonella Serovars in Poultry More Pathogenic for Humans than Others?

Willie Gregg, Callie Harris, Chris Johnson, Vivek Soni, and John J. Maurer
Department of Population Health, College of Veterinary Medicine,
The University of Georgia,
Athens GA, 30602.

Salmonella is recognized as an important zoonotic pathogen and poultry is one of the most important vehicles involved in foodborne outbreaks. The Salmonella stains that can prove to be detrimental to human and animal health are those that possess specific set of virulence genes. It is believed that the presence of certain virulence genes, associated with mobile genetic elements, contribute to the prevalence of certain epidemiologic strains seen in both humans and poultry populations. In this study, we used DNA-DNA hybridization to screen approximately 900 Salmonella isolates, from poultry integrator and primary breeder company that supply the poultry stock, for virulence genes including sseI, grvA, sodC1, and spvC associated with prophage and plasmid genomes. We used Chi-squared test to correlate virulence genotype with Salmonella serovars isolated from poultry farms in Northeast Georgia. Of 8 virulence genes screened, we found that four (sseI, sodC1, grvA, and spvC) were strongly associated with specific Salmonella serovars (Chi-squared test p<0.05), most notably S. Typhimurium and S. Enteritidis. In a screen, of Salmonella recently isolated from broiler-breeder farms and primary breeder company, 15% of the isolates possessed these four virulence genes. We believe certain Salmonella serotypes are more infectious and virulent than others due to the transmission of prophages and plasmids among salmonellae population. Focus on eliminating specific Salmonella strains, ex. those possess these phage and plasmid associated virulence genes, from poultry flocks would prove most effective at reducing human illnesses.