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

Background: The lack of new antimicrobial drugs and the increased antimicrobial resistance has focused the attention on the employment of essential oils (EOs), particularly in veterinary medi-cine. Methods: EOs from Origanum vulgare L., Juniperus communis L., Cistus ladaniferus L., Citrus au-rantium L. var. amara were tested individually and as binary combinations to study: the in vitro antibacterial activity against Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), and Escherichia coli; the antioxidant capacity by redox-based assays (DPPH, ABTS and FRAP) and the in vitro anti-inflammatory activity by bovine serum albumin (BSA) denatura-tion inhibition assay. Results: A good antibacterial activity was observed for O. vulgare L. against all strains (MIC = 0.0312%–0.125%, v/v), followed by C. ladaniferus L. O. vulgare L. also provided the best results in terms of antioxidant and anti-inflammatory activity. 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, confirmed also by the reduction of bacterial biofilm, and by antioxidant and anti-inflammatory activities. Conclusions: The results suggest that EO combinations may a be 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.