Antimicrobial activity of cinnamate-eugenol: synergistic potential, evidence of efflux pumps and amino acid effects.

摘要

Bacteriostatic and bactericidal doses of mixtures of cinnamate and eugenol against Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Listeria monocytogenes and Staphylococcus aureus were determined. A combination of the 2 compounds was used to challenge these 4 bacteria, yielding a dose-dependent bactericidal or bacteriostatic effect. Synergistic effects were demonstrated against the 3 rod-shaped bacteria, L. monocytogenes, E. coli O157:H7 and Salmonella Typhimurium, while for S. aureus, the mixture showed no synergistic activity. Notably, in the case of S. aureus, the interaction term was not significant (P > 0.05), consistent with an additive but not synergistic effect between cinnamate and eugenol. The optimal combination of 1.35mM cinnamate and 0.12mM eugenol was bactericidal. Data showed that in response to this antimicrobial activity, these strains expressed efflux pumps. Additionally, the effect of 3 amino acids on the bactericidal activity of these compounds was investigated. Bactericidal activity was interrupted by the presence of cysteine and proline, but not tyrosine. This effect was reversed when larger doses of eugenol and cinnamate were tested. It is concluded that a combination of cinnamate and eugenol produces a synergistic bactericidal effect against L. monocytogenes, E. coli O157:H7 and Salmonella Typhimurium.