Antibacterial activity of essential oils, their blends and mixtures of their main constituents against some strains supporting livestock mastitis Filippo Fratini a,e , Sergio Casella b , Michele Leonardi b , Francesca Pisseri c , Valentina Virginia Ebani a,e , Laura Pistelli d,e, ⁎, Luisa Pistelli b,e a Dipartimento di Scienze Veterinarie, University of Pisa, Viale delle Piagge 2, 56124 Pisa, Italy b Dipartimento di Farmacia, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy c Scuola CIMI-Koinè, Via Ugo Bassi 2, Roma, Italy d Dipartimento di Scienze Agrarie, Alimentari e Agro-ambientali, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy e Centro Interdipartimentale di Ricerca "Nutraceutica e Alimentazione per la Salute University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy article info abstract Article history: Received 29 January 2014 Accepted in revised form 31 March 2014 Available online 13 April 2014 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, Staphylo- coccus 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. © 2014 Elsevier B.V. All rights reserved. Keywords: Mastitis infection GC–MS analysis Staphylococcus sp. Carvacrol Thymol p-Cymene 1. Introduction Mastitis is defined as an inflammatory reaction of the mammary gland induced when pathogenic microorganisms in the udder produce toxins that are harmful to the mammary gland [1]. As a result of the inflammation, milk composition is altered with a decrease of caseins/lactose synthesis and fat quality [2,3]. Mastitis can be clinical or subclinical and represents a relevant damage for the breeders because of milk waste, loss of udder functionality and sometimes death of the animal. The clinic forms of mastitis can be hyper acute, acute and chronic. The first two forms are mainly caused by Staphylococcus aureus and occasionally by Pseudomonas aeruginosa and Pasteurella spp. (Mannheimia), while Mycoplasma agalactiae, Streptococcus agalactiae, and Staphylococcus epidermidis are often involved in the chronic Fitoterapia 96 (2014) 1–7 Abbreviations: EO, essential oil. ⁎ Corresponding author at: Dipartimento di Scienze Agrarie, Alimentari e Agro-ambientali, University of Pisa, Italy. Tel.: +39 0502216536; fax: +39 0502216532. E-mail addresses: filippo.fratini@virgilio.it (F. Fratini), sergio.casella@ymail.com (S. Casella), mikileonardi@gmail.com (M. Leonardi), francesca.pisseri@vet.unipi.it (F. Pisseri), vebani@vet.unipi.it (V.V. Ebani), laura.pistelli@unipi.it (L. Pistelli), luisa.pistelli@farm.unipi.it (L. Pistelli). http://dx.doi.org/10.1016/j.fitote.2014.04.003 0367-326X/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Fitoterapia journal homepage: www.elsevier.com/locate/fitote