Osmotic Stress Adaptation of Poultry-Associated Salmonella Infantis and Its Implications for Food Safety

Salmonella enterica serovar Infantis, an important zoonotic pathogen with increasing prevalence in the poultry industry, often persists despite rigorous disinfection. This study characterized the transcriptomic response of the multidrug-resistant Salmonella Infantis strain SE016, isolated from a poultry plant, to osmotic stress, a condition frequently induced by the use of industrial disinfectants. Phenotypic assays demonstrated that stress induced by 15% sucrose simulated osmotic stress, producing a drastic reduction in flagellar motility and a significant increase in biofilm formation in SE016, compared with a susceptible control strain. RNA-seq analysis indicated that SE016 undergoes coordinated transcriptional changes consistent with altered metabolic activity under osmotic stress. Key mechanisms include metabolic braking through repression of tricarboxylic acid (TCA) cycle genes (icd, mdh) and induction of anaerobic nitrate respiration (narGHI, narZWV) as an energy contingency. Furthermore, SE016 showed increased expression of genes involved in osmoprotectant uptake, including the proU transport system and endogenous trehalose synthesis (ostAB) while repressing proline degradation (putA). Furthermore, robust biofilm formation was observed despite repression of the master regulator csgD. This was mediated by the CsgD-independent induction of the diguanylate cyclase adrA, activating cellulose synthesis (bcs). These results suggest that pathways associated with the OmpR/EnvZ two-component system may contribute to energy balance and persistence-related phenotypes under industrial-like stress conditions.