Antimicrobial and anti-biofilm activity of Epigallocatechin gallate against Vibrio parahaemolyticus

Vibrio parahaemolyticus enhances its environmental persistence and antimicrobial tolerance by forming biofilms. This study investigated the antimicrobial and anti-biofilm activities of (-)-Epigallocatechin gallate (EGCG) against the pandemic V. parahaemolyticus RIMD2210633 (O3:K6). EGCG significantly inhibited bacterial growth, motility, and biofilm formation in a concentration-dependent manner. Sub-inhibitory concentrations (4 and 8 µg/mL) effectively reduced biofilm biomass, altered colony morphology, and diminished extracellular polymeric substances, and exerted potent bactericidal activity against preformed biofilms. EGCG also exhibited bactericidal effects in shrimp meat and impeded biofilm formation on seafood-related surfaces. It also significantly attenuated bacterial virulence in both in vitro (HeLa cell) and in vivo (Galleria mellonella larva) infection models. Mechanistically, RNA sequencing revealed that EGCG induced transcriptomic reprogramming, with 500 differentially expressed genes (DEGs) involved in key pathways such as c-di-GMP signaling, flagellar assembly, type III/VI secretion systems, and stress responses; biochemical assays confirmed that EGCG directly reduced intracellular c-di-GMP levels in a dose-dependent manner. Quantitative real-time PCR validated the expression changes in genes related to virulence, motility, biofilm, and regulation. Collectively, these findings highlight the multi-faceted anti-virulence and anti-biofilm activities of EGCG, and support its potential application as a natural antimicrobial agent in the food industry and clinical settings.