Candidosis Management : Antifungal and Immunomodulatory Properties of Tea tree oil

Candida albicans is the predominant yeast associated with oropharyngeal candidosis (OPC), which presents clinically as thrush or denture stomatitis. These infections are characterised by multispecies biofilms forming on the oral epithelium or artificial denture surfaces. Current antifungal treatments have limited success due to various resistance mechanisms, with recurring infections common. Therefore, alternative methods for suppressing or eradicating biofilms are desirable. Objectives: The aims of this study were to evaluate the effectiveness of tea tree oil (TTO) and key derivatives against biofilms formed by a panel of oral C. albicans isolates, and to assess the cytotoxic and immuno-modulatory properties of TTO and its derivatives in a clinically relevant oral cell model. Methods: Biofilms were formed on microtitre plates and treated with various concentrations of individual TTO components. Fungicidal activity was evaluated using the metabolic dye XTT. The most efficacious components were then applied to a human oral epithelial cell line (OKF6-TERT2) and the toxicity evaluated using a commercially available assay. Cells were stimulated with zymosan A (yeast cell wall polysaccharide) and treated with TTO components, and cytokine profiles analysed using a commercially available kit. Real-time PCR was also used to measure gene expression changes for selected cytokines. Results: It was shown that terpinen-4-ol (T4-ol) and α-terpineol exhibited greater anti-biofilm activity (MFC₉₀ = 0.5%) than TTO (1%). TTO and T4-ol were significantly less toxic than chlorhexidine at therapeutic levels. TTO reduced stimulatory effects of zymosan on pro-inflammatory cytokines. Conclusions: TTO-derived mouthwashes may offer a suitable alternative to conventional azole treatment, as they exhibit potent antifungal activity, are minimally toxic and can modulate inflammatory mediators.