Targeting skin-associated candida: antifungal efficacy of selected essential oils

Lopes, Ana I.; Oliveira, Cláudia S.; Pintado, Manuela E.; Tavaria, Freni K.

http://hdl.handle.net/10400.14/55109

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Abstract(s)

Background: Candida spp. are commensal yeasts that inhabit the skin and mucous membranes and are the leading cause of invasive fungal infections. Mucocutaneous candidiasis is a common condition, often treated with azoles and polyenes, which may cause side effects and foster resistance. Essential oils (EOs), natural compounds with antimicrobial activity, present a promising alternative due to their multi-target action, reducing the likelihood of resistance. Objective: To study the antimicrobial activity of three EOs – eucalyptus, lavender, and thyme – against two species of Candida (C. albicans and C. tropicalis). Methods: The antimicrobial potential of the EOs against the selected yeasts was assessed using the following tests: (i) agar diffusion assay; (ii) determination of minimum inhibitory (MIC) and fungicidal concentrations (MFC); (iii) growth inhibition curves at MIC, 2×MIC, and ½MIC; (iv) anti-biofilm activity at MIC, ½MIC, and ¼MIC; (v) membrane integrity analysis by flow cytometry using propidium iodide (PI) and thiazole orange (TO); and (vi) fluorescence microscopy of yeasts exposed to eucalyptus EO at ¼MIC. Results: C. albicans inhibition zones were 5.13 mm (eucalyptus), 5.0 mm (lavender), and complete inhibition with thyme EO. All EOs fully inhibited C. tropicalis. MIC and MFC values ranged from 0.08% to 2.5% (v/v), with thyme EO having the lowest values for both yeasts. Inhibition curves confirmed MIC results. Thyme EO also showed the greatest inhibition of biofilm formation. Flow cytometry revealed membrane damage in both species, with C. tropicalis showing a higher proportion of dead and damaged cells. Thyme EO consistently induced the highest levels of cell damage across all concentrations tested. Fluorescence microscopy supported flow cytometry findings, revealing live (green), injured (yellow), and dead (red) cells following EO exposure. Conclusion: All tested EOs displayed antifungal activity, with thyme EO being the most effective. C. albicans was more resistant than C. tropicalis, highlighting species-specific EO sensitivity.

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http://hdl.handle.net/10400.14/55109

Citation

Lopes, A. I., Oliveira, C. S., Pintado, M. E., & Tavaria, F. K. (2025). Targeting skin-associated candida: antifungal efficacy of selected essential oils. Abstract from 7th European Congress on Applied Microbiology and Beneficial Microbes, Rome, Italy.