Unveiling Salmonella Derby Survival: Stress Responses to Prolonged Hyperosmotic Stress

The traditional marination process enhances food flavor and inhibits microbial growth. However, in hyperosmotic environments, microorganisms can activate stress responses to ensure survival, potentially compromising food safety. This study investigated the osmotolerance mechanisms of <i>Salmonella</i> Derby (<i>S</i>. Derby) by comparing a wild-type strain (<i>S</i>. D-WT) and an osmotolerant strain (<i>S</i>. D-OT) under NaCl-induced hyperosmotic stress. Both strains were subjected to 0.85%, 4%, and 16% NaCl for 0, 8, and 16 days, and their growth behavior, membrane integrity, intracellular osmoprotectant content, and transcription of related genes were evaluated. By day 16, both strains showed a growth delay of approximately 3 h. <i>S</i>. D-OT maintained better membrane integrity and exhibited higher intracellular levels of osmoprotectants (K⁺, trehalose, and proline), which aligned with the upregulation of the transcriptional levels of <i>kdpC</i>, <i>kuP</i>, <i>rpoS</i>, and <i>proU</i>. These findings indicated that <i>S</i>. D-OT achieved improved osmotic stress tolerance by regulating osmoprotectant synthesis and maintaining intracellular homeostasis. In contrast, <i>S</i>. D-WT displayed greater resistance to multiple antibiotics (gentamicin, ciprofloxacin, trimethoprim-sulfamethoxazole, and chloramphenicol) under 4% and 16% NaCl conditions, which may pose a higher food safety risk. Overall, this study provides insights for improving microbial control strategies in preserved foods and mitigating foodborne disease risks.