Individual and synergistic antimicrobial effects of nisin, resveratrol, naringenin, and saponins against Salmonella Typhimurium biofilms

AIMS: This study investigates the individual and synergistic antibacterial and antibiofilm effects of nisin, resveratrol, naringenin, and saponins against Salmonella enterica subsp. enterica serovar Typhimurium ATCC 14028. The objective is to identify safe, effective compound combinations to combat Salmonella persistence in food processing environments, which is often caused by biofilm formation. METHODS AND RESULTS: Using broth microdilution, checkerboard synergy testing, and biofilm/motility assays, the antimicrobial effects were evaluated. Molecular docking and qPCR provided mechanistic insights. Naringenin and resveratrol demonstrated significant antibacterial and antibiofilm activities, especially when combined. The resveratrol-naringenin combination produced the strongest synergistic effect (Fractional Inhibitory Concentration Index (FICI) value of 0.1875), effectively inhibiting bacterial growth and biofilm formation. Molecular analyses revealed this combination targets key proteins (e.g. BcsA, CsgD) and significantly downregulates genes for biofilm formation, quorum sensing, and motility. CONCLUSIONS: The combination of resveratrol and naringenin is a promising natural strategy for controlling Salmonella. Its synergistic action impairs bacterial viability and disrupts biofilm by targeting essential proteins and downregulating key virulence genes.