Investigation of the molecular basis of variation in food chain related stress response of Salmonella enterica

Pye, Hannah (2022) Investigation of the molecular basis of variation in food chain related stress response of Salmonella enterica. Doctoral thesis, University of East Anglia.

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Non-Typhoidal Salmonella is an important foodborne pathogen annually causing over 120,000 deaths worldwide. Cases and outbreaks of salmonellosis are typically associated with the consumption of contaminated animal products and more recently with a variety of other food types including fruits, vegetables, and confectionaries. Food manufacturers implement hurdle technology by combining more than one approach to prevent foodborne contamination, such as the use of preservatives, refrigeration, and high temperatures. Salmonella has the potential to evade these methods by invoking a stress response and can adapt to ever-changing environmental pressures. Multiple Salmonella strains are used simultaneously in a strain cocktail to assess survival during food challenge tests, but certain strains possess an increased resistance to stress, thus posing a greater risk to food safety. The variability of Salmonella survival in stresses relevant to food production was assessed to identify strains of importance and to determine the molecular mechanisms of stress tolerance. Sub-lethal heat treatment in a vegetarian food matrix, survival in desiccated conditions and growth in the presence of NaCl and organic acids were all investigated in a variety of Salmonella strains. S. Gallinarum strain 287/91 and S. Typhimurium strain SO1960-05 exhibited an increased sensitivity to stress. Variation in the survival of strains in stress conditions, indicated that response to stress is strain specific. A whole genome functional screen using transposon directed insertion site sequencing (TraDIS) contained 610,000 unique insertions in S. Typhimurium ST4/74 and was used to identify conditionally essential genes. Single gene knockouts of conditionally essential genes were constructed in ST4/74 to validate TraDIS results. An understanding of the diverse metabolic capacities of Salmonella strains, genes with central roles in food chain stress response, and phenotypic variation will result in a verified selection of target strains for process validations, improved processing, and more reliable risk assessments.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Kitty Laine
Date Deposited: 24 May 2023 13:50
Last Modified: 24 May 2023 13:50


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