Antibiofilm activity of rosmarinic acid against Vibrio parahaemolyticus in vitro and its efficacy in food systems

Vibrio parahaemolyticus is a crucial foodborne pathogen related to seafood-borne illnesses. V. parahaemolyticus has a strong capacity to form biofilm and withstand common biocides, which increases its persistence and contamination in food chains. Currently extensive use of chemical disinfectants to control biofilm has potential health concern and imprudent usage may also increase the emergence of antimicrobial resistant strains. Therefore, novel alternative, efficient but consumer-friendly agents for curtailing biofilms are urgently necessitated. Rosmarinic acid (RA) is broadly applied in cosmetic, pharmaceutical and food industries and displayed good antibacterial properties. The objectives of this study were to assess the impact of sub-inhibitory RA on V. parahaemolyticus biofilm formation and explore the underlying mechanisms through measuring its micro-structure, its components and expression of bacterial biofilm-related genes, and its potential for application in food systems. RA at sub-inhibitory concentrations markedly suppressed biofilm formation in laboratory and food broths ranging from 19.41 % to 68.97 %, which was supported by crystal violet staining. RA restricted the motility, autoinducer-2 secretion and extracellular polymeric substance production and metabolic activity. Furthermore, RA effectively reduced biofilm biomass on various food surfaces ranging from 7.95 % to 26.72 %, and food contact surfaces by more than 9.42 %. Real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) exhibited that RA repressed the transcription levels of genes-associated biofilm. Moreover, molecular docking assay demonstrated that RA had the potential to bind directly to RcpA. To sum up, this study identified RA as a potential natural antibiofilm agent for V. parahaemolyticus and supported its potential application in food industries.