Binary Combinations of Essential Oils: Antibacterial Activity Against Staphylococcus aureus, and Antioxidant and Anti-Inflammatory Properties

Background: The lack of new antimicrobial drugs and increased antimicrobial resistance has focused attention on the employment of essential oils (EOs) in human and veterinary medicine. The aim of this study was to test new binary associations between known and uncommon EOs. Methods: EOs from Origanum vulgare L., Juniperus communis L., Cistus ladaniferus L., Citrus aurantium L. var. amara were tested individually and in binary combinations to study, as follows: antibacterial activity against Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) and Escherichia coli; antioxidant capacity via redox-based assays (DPPH, ABTS and FRAP); and anti-inflammatory activity via the bovine serum albumin denaturation inhibition assay. Results: O. vulgare L. showed good antibacterial activity against all strains (MIC = 0.03-0.12%, v/v), followed by C. ladaniferus L., and also had the best antioxidant and anti-inflammatory activities. Synergistic and additive effects were observed for the EO combinations O. vulgare L./C. ladaniferus L. and O. vulgare L./J. communis L. against S. aureus and MRSA, respectively. A reduction in biofilm was noted. Antioxidant and anti-inflammatory activities were also detected. Conclusions: The results suggest that EO combinations may be a promising strategy in veterinary settings for the treatment of infectious diseases caused by S. aureus, including drug-resistant and biofilm-forming strains accompanied by oxidative stress and inflammation.