Evaluation of antibacterial and antibiofilm properties of Minthostachys verticillata essential oils against bovine Staphylococcus aureus strains

Abstract

Staphylococcus aureus is the main important mastitis pathogen. Treatment strategies using medicinal plants are novel alternatives. The aim of the present study was to evaluate the antibacterial activity and the biofilm inhibitory effects in vitro of two Minthostachys verticillata essential oils, EO1 and EO2, collected from different regions of Argentina against bovine Staphylococcus aureus. Chemical composition and cytotoxic effects were determined. Furthermore, antimicrobial activity of EO1 was evaluated in vivo as topical application emulsion in dairy cows after milking. Chemical profile of both oils showed different percentages among the major chemical compounds. In addition, MTT reduction method showed that oils were not toxic up to the concentration of 250 μg/ml. Results obtained revealed that oils were able to inhibit the growth and reduce biofilm production, from 36.4% to 96.06%. EO1 inhibited bacterial growth at lower concentrations compared to EO2 and it was selected for the emulsion preparation. Cows were treated with EO1 emulsion, at 4 and 6 mg/ml and it was able to reduce the bacterial load, showing an antibacterial effect. Both oils exhibited antibacterial and anti-biofilm activities against test bacteria showing that Minstosthachys verticillata essential oil may have potential application as bactericidal agent against S. aureus.