Climate change-driven risks on contamination routes and timing, and phage control of Salmonella on leafy greens

This study investigated the persistence and control of S. enterica serovar Newport on garden cress under warming temperature scenarios (15°C, 17°C, 19°C, 21°C), simulating climate change-relevant conditions. Two contamination routes-seed and irrigation-were tested with irrigation applied at different plant growth stages to assess the impact of contamination timing too. In addition, the study evaluated the effectiveness of preharvest bacteriophage irrigation applied at various intervals prior to harvest. Results showed that both contamination routes supported long-term survival, with the greatest persistence at 15°C. Late-stage contamination through irrigation resulted in higher bacterial loads at harvest, posing greater food safety risks. While a washing step significantly reduced Salmonella levels, especially in later contamination scenarios, it was insufficient to fully remove strongly attached bacterial populations across all cases. Bacteriophage irrigation achieved up to 2.2 log MPN/g reduction when applied close to harvest, particularly when combined with washing. Beyond expanding the mechanistic understanding of Salmonella-plant interactions, these findings illustrate how temperature dynamics, contamination timing, and exposure routes collectively influence bacterial persistence under warming scenarios relevant to climate change, while also demonstrating the potential of a targeted preharvest intervention strategy with significant control efficacy.