|Nisbet, David - Dave|
Submitted to: Journal of Food Safety
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/5/2002
Publication Date: 7/20/2002
Citation: NUTT, J.D., KUBENA, L.F., NISBET, D.J., RICKE, S.C. VIRULENCE RESPONSE OF A SALMONELLA TYPHIMURIUM HILA:LACZY FUSION STRAIN TO SPENT MEDIA FROM PURE CULTURES OF SELECTED BACTERIA AND POULTRY CECAL MIXED CULTURE. JOURNAL OF FOOD SAFETY. 2002. v. 22. p. 169-181. Interpretive Summary: In recent years, there has been increased concern regarding the contamination of products with salmonellae. Poultry products are among those products sometimes contaminated with various types of Salmonella and are a source of human salmonellosis. Adequate information is not available on the various factors that influence successful colonization and infection of Salmonella within a host. In this study, growth media was obtained after pure cultures of selected bacteria or poultry cecal mixed culture had grown on it (spent media) and then used to determine if the capacity of Salmonella Typhimurium to infect was changed. The spent media generated by bacteria from a mixed culture cecal sample gave a lower capacity for Salmonella Typhimurium to infect than did spent media generated by the Salmonella Typhimurium strain in spent media samples, thus suggesting that the normal gut microflora in chickens could limit Salmonella Typhimurium infection by decreasing its capacity to infect. This information can be used by the poultry industry in planning an overall salmonellae protection plan to insure a continued supply of safe poultry products for consumers.
Technical Abstract: Virulence gene expression in Salmonella is triggered by a variety of environmental factors including changes in the gastrointestinal environment of birds during different dietary regimes. The objective of this study was to determine if growth of specific microorganisms alters the environmental conditions sufficiently to signal Salmonella Typhimurium virulence response. Spent media was obtained from a Salmonella Typhimurium hilA:lacZY fusion strain, a poultry Salmonella Typhimurium strain, Escherichia coli K12, and Lactobacillus caseii. Spent media samples were collected after 2, 4, 8 and 24 h of growth in brain heart infusion broth (BHI) and M9 media. B-galactosidase assays were performed on the samples to determine virulence expression. Virulence response to Salmonella spent media was 2-fold greater than Lactobacillus spent media at 4, 8 and 24h growth (P<0.05). Virulence expression almost doubled when exposed to Salmonella Typhimurium (NONA) spent media compared to mixed culture spent media at 4 h, and Salmonella Typhimurium (NONA) was significantly higher than mixed culture spent media at 24 h P<0.05). Based on these results, it appears that growth of similar bacterial species may alter the composition of rich media sufficiently to influence virulence.