Antibacterial activity of essential oils, their blends and mixtures of their main constituents against some strains supporting livestock mastitis

Ten of the most known and used commercial essential oils (Cinnamomum zeylanicum L., Citrus bergamia Risso, Eucalyptus globulus Labill., Foeniculum vulgare Mill., Origanum majorana L., Origanum vulgare L., Rosmarinus officinalis L., Satureja montana L., Thymus vulgaris L. ct. carvacrol, Thymus vulgaris L. ct. thymol) were tested against six bacteria strains Staphylococcus aureus, Staphylococcus chromogenes, Staphylococcus sciuri, Staphylococcus warneri, Staphylococcus xylosus and Escherichia coli, responsible for mastitis in animals. The best results were achieved by S. montana, T. vulgaris ct. thymol and O. vulgare. Two binary mixtures of essential oils (EOs) were prepared of S. montana and T. vulgaris ct. thymol (ST) and of S. montana and O. vulgare (SO). The ST mixture exhibited the best inhibitory activity against all the tested bacterial strains. Two artificial mixtures of carvacrol/thymol (AB) and carvacrol/thymol/p-cymene (CD) were prepared and tested against all of the bacterial strains used. The results exhibited a general reduction of the inhibitory activity of mixture AB, although not reaching the inhibition of the ST and SO mixtures. However the mixture CD presented an apparent strong inhibition against S. aureus and S. sciuri. The EO mixtures and the mixture CD represent promising phytotherapic approaches against bacteria strains responsible for environmental mastitis.

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