title: Antimicrobial activity of binary combinations of natural and synthetic phenolic antioxidants against Enterococcus faecalis.
abstract: This study investigated the antimicrobial activity of 3 natural (thymol, carvacrol, and gallic acid) and 2 synthetic [butylated hydroxyanisole (BHA) and octyl gallate] phenolic compounds, individually and in binary combinations, on 4 dairy isolates of Enterococcus faecalis with different virulence factors (β-hemolytic, gelatinase, or trypsin activities; acquired resistance to erythromycin or tetracycline; and natural resistance to gentamicin). A checkerboard technique and a microdilution standardized method were used. All compounds individually tested exhibited antimicrobial activity against E. faecalis, with minimal inhibitory concentrations (MIC) ranging from 30 μg/mL (octyl gallate) to 3,150 μg/mL (gallic acid), although no significant differences were detected among strains to each phenolic compound. Carvacrol in combination with thymol or gallic acid, and gallic acid combined with octyl gallate showed partial synergistic inhibition of all E. faecalis strains. The most effective combinations were thymol+carvacrol and gallic acid+octyl gallate, as the MIC for each of these compounds was reduced by 67 to 75% compared with their respective individual MIC. These results highlight the possibility of using combinations of these phenolic compounds to inhibit the growth of potential virulent or spoilage E. faecalis strains by reducing the total amount of additives used in dairy foods.
authors.affiliation: Department of Molecular Biology, University of León, 24071 León, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Gutiérrez-Fernández
authors.forename: M R
authors.initials: MR
authors.lastname: García-Armesto
authors.forename: R
authors.initials: R
authors.lastname: Alvarez-Alonso
authors.forename: P
authors.initials: P
authors.lastname: del Valle
authors.forename: D
authors.initials: D
authors.lastname: de Arriaga
authors.forename: J
authors.initials: J
authors.lastname: Rúa
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D002083:Butylated Hydroxyanisole / Q000494:pharmacology; D000081007:Cymenes; D004357:Drug Synergism; D013293:Enterococcus faecalis / Q000187:drug effects*; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D039821:Monoterpenes / Q000494:pharmacology; D013943:Thymol / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D000975:Antioxidants; D000081007:Cymenes; D039821:Monoterpenes; C016627:octyl gallate; D002083:Butylated Hydroxyanisole; D013943:Thymol; D005707:Gallic Acid; C073316:carvacrol
keywords: Enterococcus faecalis; antimicrobial activity; phenolic compound; synergistic effect