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

Abstract

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.