Cold-induced transcriptomic responses are associated with strain-dependent Salmonella enterica persistence in...

Salmonella enterica is a leading cause of foodborne outbreaks linked to leafy greens. Refrigerated storage is a cornerstone of leafy-green safety, yet strain-level variation in the persistence of internalized S. enterica under these conditions remains poorly understood. Screening of eleven S. enterica strains revealed marked differences in their persistence within detached romaine lettuce leaves stored at 10 °C. Two isolates, belonging to serovars Montevideo and Newport, displaying contrasting persistence phenotypes were selected for detailed analysis, and these differences were confirmed at 4 °C. To investigate transcriptional responses associated with this variation, we profiled transcriptomic responses to cold stress in nutrient-rich medium by RNA-seq and evaluated post-cold recovery. Both isolates grew similarly at 28 °C but diverged at 4 °C, with the Montevideo strain maintaining higher growth capacity. Functional enrichment of KEGG pathways and Gene Ontology terms revealed shared repression of central metabolic and energy-producing pathways, coupled with induction of stress-response processes. Genes associated with general stress responses, cold-shock functions, and envelope integrity were more prominently represented among the induced responses of the Montevideo strain after cold exposure. These findings indicate that strain-dependent differences in Salmonella persistence during refrigerated lettuce storage are associated with distinct transcriptional responses to cold stress and post-cold recovery phenotypes observed in cultured bacteria. Consideration of strain-level variation may improve interpretation of pathogen persistence during leafy-green storage and inform future microbial risk assessments.