In Vitro Antifungal Effect of Selected Essential Oils Against Clinical Isolates Causing Fungal Keratitis: A Preliminary Pharmacological Evaluation

Background/Objectives: Fungal keratitis (FK) is a current challenge in ophthalmology due to its association with severe visual impairment and the limitations of current antifungal therapies. We aim to evaluate the antifungal activity of essential oils (EOs) from the aromatic and medicinal plants Cymbopogon citratus and Lavandula pedunculata against selected FK pathogens collected from FK patients in two Portuguese hospitals. Methods: The antifungal activity of the EOs was tested at concentrations of 25%, 50%, 75%, and 100% for up to 7 days using the solid-phase disk diffusion in vitro assay. Results: Candida albicans was the most prevalent pathogen (28.6%), followed by Candida parapsilosis (21.4%) and Dicyma olivacea (14.2%). The other identified species were Aspergillus fumigatus and Scedosporium boydii (7.1%). Clinical diagnostic methodologies showed agreement with the molecular identification. Cymbopogon citratus EO showed higher antifungal activity than Lavandula pedunculata EO. The highest antifungal activity was observed against Aspergillus fumigatus and Scedosporium boydii (inhibition zone diameter, IZD = 90.0 mm) after 7 (Cymbopogon citratus EO) or 3 days of incubation (Lavandula pedunculata EO). While the antifungal activity of Cymbopogon citratus EO was maintained during the study (for Aspergillus fumigatus, Candida albicans, and Scedosporium boydii), the antifungal activity of Lavandula pedunculata EO decreased with time. Conclusions: Cymbopogon citratus EO and Lavandula pedunculata EO showed optimal antifungal activity against molds (Aspergillus fumigatus and Scedosporium boydii) after 3 days of incubation. Against yeasts (Candida albicans and Candida parapsilosis), the EOs showed lower activity. Our study sheds light on the development of new pharmacological strategies for FK based on EOs extracted from aromatic and medicinal plants.