Evaluation of the Synergistic Interaction between Satureja hortensis and Carum carvi Essential Oils and Fluconazole against Candida albicans: In Vitro

Backgrounds: Nowadays, excessive use of fungal drugs has led to the development of drug-resistant fungi, making it necessary to find natural and herbal antifungal agents. This in-vitro study aimed to evaluate the interactions of Satureja hortensis and Carum carvi essential oils together and each essential oil with fluconazole against Candida albicans ATCC-10231. Materials Methods: In this study, antifungal properties of different concentrations of S. hortensis (0.0244-1.56 μL/mL) and C. carvi (0.39-25 μL/mL) were investigated by broth-microdilution method based on CLSI M27-A3 and M27-S4 standard documents. The interactions of essential oils together and each essential oil with fluconazole were evaluated by checkerboard assay. Then using the ΣFIC index, the interaction results were interpreted. Findings: S. hortensis essential oil showed higher antifungal activity than C. carvi essential oil. (MIC/MFC: S. hortensis: 1.56/3.12 μL/mL and C. carvi: 12.5/25 μL/mL). The interaction between S. hortensis essential oil and fluconazole was on the synergic and additive borderline (FICI=0.508), the interaction between C. carvi essential oil and fluconazole was additive (FICI=0.62), and C. carvi and S. hortensis essential oils showed no interaction together (FICI=2.015). Conclusion: The essential oils of S. hortensis and C. carvi separately exhibited powerful antifungal activities. The use of S. hortensis essential oil at a very low concentration along with fluconazole caused an interaction very close to synergy and increased fluconazole antifungal activity. Therefore, S. hortensis is a potential candidate for combined use with fluconazole to treat C. albicans related diseases.