Effect of tea tree essential oil on microorganisms 2. Evaluation of fungal reaction to tea tree oil under different conditions

Abstract

Antifungal activity of Melaleuca alternifolia (tea tree) oil was determined mixing the oil with the culture medium (MEA, Malt Extract Agar) and seeding a fungus suspension or mycelium blocs. We report the fungitoxic activity of tea tree oil used at different concentrations (from 1.2 to 0.05% v/v), against 11 isolates of airborne fungi: Chaetomium globosum, Stachybotrys chartarum (= S. atra) and Ulocladium atrum (= Stemphylium atrum). Two sets of experiments were conducted: tea tree oil and its volatile fraction were tested against fungi during separate in vitro investigations. The results showed a strong fungicidal activity of tea tree oil at 0.75% concentration against all fungal isolates investigated. Lower concentrations (0.25–0.5%) inhibited conidia germination, germ tube elongation and mycelial growth of fungi. The indoor air contamination by fungi and their growth on building materials depend on moisture conditions. Effects of material moisture content (75% and 100% MC) on fungus U. atrum resistance to tea tree oil vapor used as a disinfectant was investigated. A correlation of the viable U. atrum conidia levels and material moisture content was detected for each fungus exposure to tea tree oil vapor. Keywords: Melaleuca, Myrtaceae, essential oil, anti-fungal activity, airborne fungi, moisture conditions