Purpose: The present study investigated the efficacy of sub-inhibitory concentrations of phytochemicals in inhibiting quorum sensing regulated phenotypes, biofilm formation and in vivo virulence in foodborne pathogens.
Methods: The phytochemicals used in the study were trans-cinnamaldehyde, curcumin, quercetin, phellandrene, caryophellene and berberine against the foodborne bacteria Pseudomonas fluorescens, Salmonella enterica serovar Typhimurium, Escherichia coli and Vibrio parahaemolyticus. Quorum-sensing inhibition was determined by using the biosensor strains of Chromobacterium violaceum, P. aeruginosa PA01 and molecular docking studies. Antibiofilm activity of phytochemicals was examined by microtiter plate assays and fluorescence microscopy. In vivo efficacy of the phytochemicals was assessed using Caenorhabditis elegans model.
Results: The phytochemicals used in the study were capable of inhibiting quorum-sensing, preventing biofilm formation and inactivating mature biofilms of foodborne pathogens in the concentration ranging from 1.8 to 62.5 µg/ml. Caryophyllene and phellandrene inhibited biofilm formation by reducing metabolic activity and exopolymeric substance production at 0.019 µg/ml and 0.038 µg/ml, respectively (P < 0.05). In vivo virulence studies revealed that the tested phytochemicals had a protective effect on C. elegans fed on the foodborne pathogen Salmonella enterica serovar Typhimurium.
Significance: Results suggest that the phytochemicals capable of inhibiting biofilm formation and virulence production in foodborne pathogens could potentially be used to control biofilms in food processing environments and incorporated in packaging films to enhance food safety.