Effects of oregano, carvacrol and thymol on Staphylococcus aureus and Staphylococcus epidermidis biofilms

1 Dipartimento Farmaco-Biologico, Facoltà di Farmacia, Università degli Studi di Messina, Villaggio Annunziata, 98168 Messina, Italy 2 Direzione Ricerca, Sviluppo & Innovazione, SIFI SpA, Via Ercole Patti 36, Lavinaio, 95020 Catania, Italy 3 Dipartimento di Chimica Bioorganica e Biofarmacia, Università di Pisa, Via Bonanno 33, 56126 Pisa, Italy Correspondence Antonia Nostro atnostro{at}pharma.unime.it Received 27 June 2006 Accepted 18 December 2006 The aim of this study was to evaluate the effect of oregano essential oil, carvacrol and thymol on biofilm-grown Staphylococcus aureus and Staphylococcus epidermidis strains, as well as the effects of the oils on biofilm formation. For most of the S. aureus ( n =6) and S. epidermidis ( n =6) strains tested, the biofilm inhibitory concentration (0.125–0.500 %, v/v, for oregano, and 0.031–0.125 %, v/v, for carvacrol and thymol) and biofilm eradication concentration (0.25–1.0 %, v/v, for oregano and 0.125–0.500 %, v/v, for carvacrol and thymol) values were twofold or fourfold greater than the concentration required to inhibit planktonic growth. Subinhibitory concentrations of the oils attenuated biofilm formation of S. aureus and S. epidermidis strains on polystyrene microtitre plates. Abbreviations: BEC, biofilm eradication concentration; BIC, biofilm inhibitory concentration; MBC, minimum bactericidal concentration.