Evaluation of antibiofilm efficacy of essential oil components β-caryophyllene, cinnamaldehyde and eugenol alone and in combination against biofilm formation and preformed biofilms of Listeria monocytogenes and Salmonella typhimurium.

The aim of this study was to examine whether the process of initial colonization and the formation of mature biofilm structure of foodborne bacterial pathogens Listeria monocytogenes and Salmonella typhimurium can be impeded by active essential oil components β-caryophyllene, cinnamaldehyde and eugenol at their individual and combined effects. Among the essential oil components tested, cinnamaldehyde and eugenol at their individual effect showed >50% degradation in biofilm biomass against preformed (matured) biofilms of both the studied bacteria, whereas β-caryophyllene failed to do so. In combination, cinnamaldehyde/eugenol blend showed synergistic antibiofilm efficacy against preformed biofilms of both the studied bacteria L. monocytogenes (FICI: 0·24) and S. typhimurium (FICI: 0·40), whereas other tested combinations showed additive antibiofilm efficacy with FICI ranged from 2·02 to 2·35. Essential oil components alone and in combination also showed much higher inhibition effect on biofilm formation at the initial stage compared to their inhibition effect on preformed biofilms. The results provide evidence that cinnamaldehyde/eugenol combination may help in designing a more potent novel, natural antibiofilm blend at sufficiently low concentrations in the food and pharmaceutical industries. SIGNIFICANCE AND IMPACT OF THE STUDY: In the present work, synergistic antibiofilm efficacy of cinnamaldehyde/eugenol combination against established biofilms of foodborne bacterial pathogens Listeria monocytogenes and Salmonella typhimurium has been reported. These synergistic interactions may help in designing a more potent, safe and effective novel natural antibiofilm agent in food and pharmaceutical industries. Besides, this combination will also be helpful in reducing concentration of individual components, thereby minimizing the undesirable impact on sensory properties of food. To our knowledge, this is the first time, synergistic antibiofilm efficacy of cinnamaldehyde/eugenol blend against established biofilms of foodborne bacterial pathogens has been reported.