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Evaluation of the Risk of Induction and Selection of More Virulent Salmonellas by Exposure to Food Production Related Stress

Health Protection Agency
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This project aims to determine if Salmonellas with increased stress tolerance and virulence may emerge more frequently when exposed to stress encountered by bacteria from farm to fork.
  • Use PT4 and DT104 isolates containing a bioluminescent RpoS reporter to examine the effects on survival and virulence of exposure to food-associated environments.
  • Establish potentially stressful environments which are representative of the changes in pH or temperature found in the food production chain from farm to fork.
  • Examine the impact of the above stresses, both singly, in combination, and sequentially, on survival characteristics.
  • Use the bioluminescent reporter to examine the influences of the above environments on RpoS expression in the surviving population.
  • Examine how frequently mutations leading to changes in RpoS expression occur.
  • Measure the effects of stress-exposure on virulence using tissue cultures and, in limited studies, animal models.

The study aims to examine whether exposure to salmonellas with altered survival or virulence characteristics may emerge as a result of exposure to certain procedures or environments common in food production.

This study will concentrate on changes in temperature or pH and will determine if particular conditions pose a more significant risk.

More information
S. enteritidis PT4 and S. typhimurium DT104 dominate human salmonellosis (an infection caused by the Salmonella bacteria) in the UK.

Salmonellas can respond to potentially stressful environments, such as changes in temperature or pH. It has been established that stress responses are linked to the ability to cause infection and may induce more permanent changes.

Research has shown that some salmonellas, including S. enteritidis and S. typhimurium, are able to mutate with a high frequency and suggest that pre-exposure to stressful environments in food production might lead to the emergence of mutants which are better able to survive and cause infection.

The use of milder processing conditions permits salmonellas to experience sub lethal stress, which may increase further the risk of selecting for, and allowing, the survival of more stress-tolerant and virulent mutants.

Find more about this project and other FSA food safety-related projects at the Food Standards Agency Research webpage.

Funding Source
Food Standards Agency
Project number
Sanitation and Quality Standards
Viruses and Prions