Use of a Salmonella typhimurium hilA fusion strain to assess effects of environmental fresh water sources on virulence gene expression. Academic Article uri icon


  • Many fruits and vegetables are irrigated with water from rivers, lakes and even wastewater systems. Irrigation may be a route for the introduction of Salmonella. Our objectives in this study were to determine survivability and virulence expression in a strain of Salmonella typhimurium when exposed to environmental water sources. Virulence expression was measured using a beta-galactosidase assay on a hilA:lacZY fusion strain of S. typhimurium. Water samples for environmental impact studies were taken from a local pond and specific sites along the Rio Grande River, which serves as a source of irrigation water in southern Texas. There was a significant difference (p<0.05) of virulence expression among the water sites. Certain regions along the Rio Grande River yielded greater amounts of beta-galactosidase activity than others. All sites yielded at least a two-fold greater virulence response than S. typhimurium grown in brain heart infusion. Salmonella survivors were enumerated as colony forming units (CFU)/ml as plated on a selective medium for the duration of 1 week and beta-galactosidase assays were performed to determine a possible correlation between culturable cells and virulence gene expression. Bacterial cells remained viable but decreased after 7 days incubation. In conclusion, water sampled at specific locations and at different times water samples exhibited differences in virulence expression in S. typhimurium.

published proceedings

  • Water Res

author list (cited authors)

  • Nutt, J. D., Pillai, S. D., Woodward, C. L., Sternes, K. L., Zabala-Daz, I. B., Kwon, Y. M., & Ricke, S. C.

citation count

  • 16

complete list of authors

  • Nutt, JD||Pillai, SD||Woodward, CL||Sternes, KL||Zabala-Díaz, IB||Kwon, YM||Ricke, SC

publication date

  • August 2003