ANTIFUNGAL ACTIVITY OF THE ESSENTIAL OIL OF MELALEUCA-ALTERNIFOLIA (TEA TREE OIL) AGAINST PATHOGENIC FUNGI IN-VITRO

The in vitro antifungal activity of tea oil, the essential oil of Mela leuca alternifolia, has been evaluated against 26 strains of various d ermatophyte species, 54 yeasts, among them 32 strains of Candida albic ans and other Candida sp. as well as 22 different Malassezia furfur st rains. Minimum inhibitory concentrations (MIG) of tea tree oil were me asured by agar dilution technique. Tea tree oil was found to be able t o inhibit growth of all clinical fungal isolates. For the investigated dermatophytes MIC values from 1,112.5 to 4,450.0 mu g/ml with a geome tric mean of 1,431.5 mu g/ml were demonstrated. Both C. albicans strai ns and the other strains belonging to the genus Candida and Trichospor on appeared to be slightly less susceptible to tea tree oil in vitro. However, their MIC values, which varied from 2,225.0 to 4,450.0 mu g/m l (geometric mean 4,080 mu g/ml), indicated moderate susceptibility to the essential oil of M. alternifolia. The lipophilic yeast M. furfur seemed to be most susceptible to tea tree oil. MIC values between 556. 2 and 4,450.0 mu g/ml (geometric mean 1,261.5 mu g/ml) were found agai nst the tested M. furfur, strains. However, when calculated as percent age tea tree oil of the agar, the above-mentioned concentrations corre spond to 0.5-0.44% tea tree oil content. These values are far below th e usual relatively high therapeutic concentrations of the agent; appro ximately 5-10% solution or even the concentrated essential oil are use d for external treatment. In comparison with tea tree oil, in vitro su sceptibility against miconazole, an established topical antifungal, wa s tested. As expected, very low MIC values for miconazole were found f or dermatophytes (geometric mean 0.2 mu g/ml), yeasts (geometric mean 1.0 mu g/ml), and M. furfur (geometric mean 2.34 mu g/ml). It is sugge sted that the in vivo effect of tea tree oil ointment in the therapy o f fungal infections of the skin and mucous membranes as well as in the treatment of dandruff, a mild form of seborrheic dermatitis, may be a t least partly due to an antifungal activity of tea tree oil.