Strain and serovar variants of Salmonella enterica exhibit diverse tolerance to food chain-related stress

• Published in: bioRxiv
• Main Authors: Pye, Hannah V, Thilliez, Gaëtan, Acton, Luke, Kolenda, Rafał, Al-Khanaq, Haider, Grove, Stephen, Kingsley, Robert A
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 11.10.2022
• Subjects: Acetic acid; Citric acid; Desiccation; Food; Food chains; Food industry; Food processing; Food quality; Foodborne diseases; Genotypes; Heat treatments; Organic acids; Phenotypic variations; Preservatives; Refrigeration; Salmonella; Salmonella enterica; Sodium chloride; Strains (organisms); Survival; United States > US; Kentucky
• DOI: 10.1101/2022.10.11.511718

Non-Typhoidal Salmonella (NTS) continues to be a leading cause of foodborne illness worldwide. Food manufacturers implement hurdle technology by combining more than one approach to control food safety and quality, including preservatives such as organic acids, refrigeration, and heating. We assessed the variation in survival in stresses of genotypically diverse isolates of Salmonella enterica to identify genotypes with potential elevated risk to sub-optimal processing or cooking. Sub-lethal heat treatment, survival in desiccated conditions and growth in the presence of NaCl or organic acids were investigated. S. Gallinarum strain 287/91 was most sensitive to all stress conditions. While none of the strains replicated in a food matrix at 4C, S. Infantis strain S1326/28 retained the greatest viability, and six strains exhibited a significantly reduced viability. A S. Kedougou strain exhibited the greatest resistance to incubation at 60C in a food matrix that was significantly greater than S. Typhimurium U288, S Heidelberg, S. Kentucky, S. Schwarzengrund and S. Gallinarum strains. Two isolates of monophasic S. Typhimurium, S04698-09 and B54 Col9 exhibited the greatest tolerance to desiccation that was significantly more than for the S. Kentucky and S. Typhimurium U288 strains. In general, the presence of 12mM acetic acid or 14mM citric acid resulted in a similar pattern of decreased growth in broth, but this was not observed for S. Enteritidis, and S. Typhimurium strains ST4/74 and U288 S01960-05. Acetic acid had a moderately greater effect on growth despite the lower concentration tested. A similar pattern of decreased growth was observed in the presence of 6% NaCl, with the notable exception that S. Typhimurium strain U288 S01960-05 exhibited enhanced growth in elevated NaCl concentrations. An understanding of the molecular basis of phenotypic variation in response to stress has the potential to improve process validation during food challenge tests, improve processing, and result in more reliable risk assessments in the food industry. Competing Interest Statement HP received a BBSRC Industrial CASE studentship that was part-funded by Nestle. SG was a Nestle employee during the study. Nestle participated in the design of the study but played no part in the decision to publish.