Synergistic inhibition of Pseudomonas aeruginosa by EGCG and I3A: preliminary mechanisms and application in fish meat preservation

Synergistic bacteriostatic action represents a potent strategy for combating microbial contamination in the food industry. This study investigated the synergistic bacteriostatic effect of epigallocatechin gallate (EGCG) and indole-3-carboxaldehyde (I3A). Results showed a pronounced synergistic action of EGCG and I3A against diverse food spoilage microorganisms, most notably Pseudomonas aeruginosa ( P. aeruginosa ), with a fractional inhibitory concentration index (FICI) of 0.25. Further research revealed that EGCG disrupted the cell wall and cell membrane of P. aeruginosa , while supplementing I3A significantly boosted the concentration of intracellular reactive oxygen species, thereby inflicting cellular damage. Moreover, the EGCG-I3A treatment inhibited the biofilm formation of P. aeruginosa in a dose-dependent manner, with the effectiveness increasing with the quantity of I3A added. Metabolomic study revealed a perturbation in glutathione and taurine metabolic pathways post synergistic treatment, compromising redox homeostasis. This synergistic treatment also downregulated uracil, proline, and glutamate metabolites, thereby suppressing Quorum Sensing (QS) and biofilm-associated expression within P. aeruginosa . Additionally, the combination significantly inhibited P. aeruginosa growth in fish meat. In essence, this study underscored the synergistic bacteriostatic efficacy of EGCG and I3A, highlighting its potential application in food preservation.