Susceptibility of methicillin-resistant staphylococci to oregano essential oil, carvacrol and thymol

The aim of this study was to evaluate the susceptibility of methicillin-susceptible and methicillin-resistant staphylococci (MSS, MRS) to oregano essential oil, carvacrol and thymol. The commercial aerial parts of Origanum vulgare L. were hydrodistilled and the essential oil analysed by gas- chromatography/electron impact mass spectrometry. The inhibition efficacy of this essence and its major components was assayed against 26 MSS and 21 MRS, using an agar dilution method. The methicillin resistance was thoroughly typed by Epsilometer test (E-test), polymerase chain reaction for mecA gene detection and PBP2′ latex agglutination test. The results clearly demonstrated that the comparison between the susceptibility of MSS and MRS to oregano oil, carvacrol and thymol showed no significant differences (Fisher’s exact test, P>0.05). The best minimum inhibitory concentration values were reported for carvacrol (0.015–0.03%, v/v) followed by thymol (0.03–0.06%, v/v) and oregano oil (0.06–0.125%, v/v).