Beyond cold chain: Exploring bacterial-viral interactions and disinfection strategies for norovirus persistence on organic lettuce under temperature fluctuations.

Storage temperature and microbial interactions are critical to human norovirus transmission and food safety in fresh produce. This study examined the survival of murine norovirus (MNV-1), a surrogate of human norovirus, and co-contaminating bacteria on organic lettuce, being a significant vehicle, and its packaging materials during cold-chain transportation, focusing on temperature fluctuations and microbial interactions. Samples contaminated with Pseudomonas sp. SC006 [Histo-Blood Group Antigen (HBGA)-expressing bacteria], Escherichia coli O157:H7, and MNV-1 were exposed to 4°C, fluctuating temperatures between 4°C and 25°C, and a constant 25°C. Both bacteria showed temperature-dependent growth, proliferating faster at 25°C. MNV-1 survival varied with temperature, persisting longer at lower temperatures. HBGA-expressing bacteria increased MNV-1 survival during temperature fluctuations. Disinfection experiments using chlorine dioxide (ClO, initial concentration of 0.03 %, pH 1.5) revealed that the interaction between MNV-1 and Pseudomonas SC006, particularly the high expression of HBGA in SEPS-SC006, protected MNV-1. Combined ClO (180 ppm) and ultraviolet (UV, 200 mJ/cm) treatment effectively disinfected MNV-1, overcoming resistance from indigenous bacteria. Transmission electron microscopy (TEM) and molecular docking analysis showed MNV-1 particles binding to HBGA-like substances in SEPS-SC006, potentially enhancing viral resistance. Overall, temperature fluctuations and bacterial-viral interactions affected MNV-1 survival, and the combination of UV and ClO offers a promising approach for ensuring fresh produce safety throughout the food cold chain.