Mechanism of Action of Melaleuca alternifolia (Tea Tree) Oil on Staphylococcus aureus Determined by Time-Kill, Lysis, Leakage, and Salt Tolerance Assays and Electron Microscopy

Abstract

The essential oil of Melaleuca alternifolia (tea tree) has broad-spectrum antimicrobial activity. The mechanisms of action of tea tree oil and three of its components, 1,8-cineole, terpinen-4-ol, and ␣-terpineol, against Staphylococcus aureus ATCC 9144 were investigated. Treatment with these agents at their MICs and two times their MICs, particularly treatment with terpinen-4-ol and ␣-terpineol, reduced the viability of S. aureus. None of the agents caused lysis, as determined by measurement of the optical density at 620 nm, although cells became disproportionately sensitive to subsequent autolysis. Loss of 260-nm-absorbing material occurred after treatment with concentrations equivalent to the MIC, particularly after treatment with 1,8-cineole and ␣-terpineol. S. aureus organisms treated with tea tree oil or its components at the MIC or two times the MIC showed a significant loss of tolerance to NaCl. When the agents were tested at one-half the MIC, only 1,8-cineole significantly reduced the tolerance of S. aureus to NaCl. Electron microscopy of terpinen-4-ol-treated cells showed the formation of mesosomes and the loss of cytoplasmic contents. The predisposition to lysis, the loss of 260-nm-absorbing material, the loss of tolerance to NaCl, and the altered morphology seen by electron microscopy all suggest that tea tree oil and its components compromise the cytoplasmic membrane.The essential oil derived by steam distillation from the leaves of Melaleuca alternifolia is also known as tea tree oil (TTO) or Melaleuca oil. TTO is well characterized and contains approximately 100 terpenes and their related alcohols (6). The physical and chemical properties of commercial TTO are regulated by an international standard (23). TTO has antibacterial (8, 17), antifungal (18, 19), antiviral (4), and anti-inflammatory (5) properties in vitro, suggesting that it may have a role in the treatment of cutaneous infection. Clinical trials have demonstrated that TTO may be efficacious in the treatment of acne (2) and oral candidiasis (24) and in the decolonization of methicillin-resistant Staphylococcus aureus carriers (7). Although the in vitro antimicrobial activity and in vivo efficacy of TTO have been reported, less is known about its mechanism of action. Since this will have implications for its spectrum of activity, selective toxicity, and the development of resistance, we examined the mechanism of action of TTO and its components against S. aureus. MATERIALS AND METHODSTTO and components. TTO (batch 971) was kindly provided by Australian Plantations Pty. Ltd., Wyrallah, New South Wales, Australia. The levels of the components, determined by gas chromatographic analysis according to the international standard (23), were as follows: 41.5% terpinen-4-ol, 21.2% ␥-terpinene, 10.2% ␣-terpinene, 3.5% terpinolene, 2.9% ␣-terpineol, 2.5% ␣-pinene, 2.1% 1,8-cineole, 1.5% -cymene, 1% aromadendrene, 1% ␦-cadinene, 0.9% ledene, 0.9% limonene, 0.6% globulol, 0.4% sabinene, and 0.3% viridiflorol. Terpinen-4-ol and ␣-terpineol (Aldrich Chem...

Antibacterial Activity of Mentha Pulegium Essential Oil Against Avian Isolated Esbl Producing Bacteria and Its Synergistic Potential With Antibiotics

“…Moreover, because of the complex composition of essential oils, multiple nonspecific cellular targets might be implicated [39]. In bacteria, the permeabilization of the membrane is associated with loss of ions and reduction of membrane potential, collapse of the proton pump and depletion of the ATP pool.…”

Atividade antibacteriana do óleo essencial de Melampodium divaricatum (Rich.) DC., Asteraceae

“…Diversos estudos demonstram que os óleos essenciais apresentam atividade antibacteriana (Carvalho Jr et al, 2004;Mevy et al, 2007) e que sua atividade está intimamente relacionada a composição química refletindo nos possíveis mecanismos de ação destes frente às diferentes cepas bacterianas (Carson et al, 2002).…”

“…Portanto, devido ao grande número e variedade dos compostos químicos presentes nos óleos essenciais, provavelmente sua atividade antimicrobiana não pode ser atribuída a um mecanismo de ação específico (Carson et al, 2002 …”

Treatment of Prostatic Abscesses by Aspiration of the Purulent Matter and Injection of Tea Tree Oil into the Cavities in Dogs

“…TTO is an anti-inflammatory and antimicrobial agent [3,6] with potent antimicrobial activity against a broad spectrum of gram-positive and gram-negative bacteria [12,17]. Terpinen-4-ol, the main component of TTO [6,9,14], suppresses bacteria-induced inflammation [5,6], and TTO has been found to be useful in the treatment of skin and wound infections in humans [7]. TTO also has antifungal activity and has been found to be effective against dermatitis in dogs [18,22,23].…”

“…TTO has been found to have a potent antibacterial effect against many species of bacteria, including E. coli and S. aureus [1,4,11,13,17]. Its antimicrobial activity is achieved by disrupting the permeability barrier of the cell membrane structure, by the accompanying loss of chemiosmotic control [8], and by compromising the membrane [5]. Previously, the authors have attempted the treatment by removing the purulent matter from the cavities of prostatic abscesses and then injecting several antibiotics that have activity against a broad spectrum of bacteria into the cavities.…”