ANTIFUNGAL PROPERTIES OF SELECTED ESSENTIAL OILS AND PURE COMPOUNDS ON EMERGING CANDIDA NON-ALBICANS SPECIES AND UNCOMMON PATHOGENIC YEASTS

Introduction. Candida spp. are the most important cause of opportunistic mycoses worldwide. Although more than 100 species of Candida have been described, the most challenging infections are caused by C.albicans. However, other Candida species and other rare yeasts are emerging as key opportunistic pathogens. Currently, the emergence of antifungal resistance is reported worldwide and is still an unresolved problem. Existing antifungal drugs have challenges to cope with the evolving nature of drug-resistant fungal pathogens. These issues have stimulated the search for new therapeutic alternatives, including essential oils (EOs) that are now well recognized for their remarkable biological activities including an antimicrobial role. Hence, the aim of this study was to investigate the in vitro antifungal activity of nine selected EOs and some main components against Candida nonalbicans species, and other uncommon pathogenic yeasts clinical strains. Materials and Methods. Commercial EOs of Foeniculum vulgare(fennel), Lavandula vera (lavender), Melissa officinalis(lemon balm), Pinus sylvestris (pine), Salvia officinalis (sage), Thymus vulgaris (thyme red), Eugenia caryophyllata (clove), Origanum vulgare (oregano), Pelargonium asperum (geranium) and EO main components (α-pinene, carvacrol, citronellal, eugenol, ɣ-terpinene, linalool, linalyl acetate, terpinen-4-ol and thymol) has been screened for antifungal activity against 47 different clinical Candida non-albicans(C.krusei, C.parapsilosis, C.valida, C.lusitaniae, C.norvegensis) and uncommon pathogenic yeasts (Pichia etchellsii/carsonii, Kloechera japonica, Saccharomyces cerevisiae, Sporobolomyces salmonicolor) clinical strains. Fluconazole (FLC) and voriconazole (VRC) were used as positive controls.We evaluated the Minimum Inhibitory Concentration(MIC) and the Minimum Fungicidal Concentration(MFC)of EOs, EO main components and drugs according to the CLSI M27-A3 with some modifications. The final concentrations ranged from 0.0019-1% v/v for EOs and components. Results. Pine and lemon balm EOs showed the highest antifungal activity against non-albicans Candida, with MIC range of 0.03-0.12%(v/v).Other most active EOs were clove and geranium EOs (MIC range 0.06-0.25%v/v).Between compounds, α-pinene demonstrated the greatest inhibitory effect (MIC range 0.002-0.016% v/v).As regard uncommon pathogenic yeasts, oregano, pine, thyme red, α-pinene, carvacrol, eugenol and thymol showed the highest activity in vitro. Discussion and Conclusions. These data showed a promising potential application of EOs as natural adjuvant for management of infections by emerging Candida non-albicans species and uncommon pathogenic yeasts. EOs and their components studied encourage adequately controlled and randomized clinical investigations