Morphological Changes in Fungal Elements and Antifungal Drug Susceptibility in an Ex Vivo Model of Fungal Keratitis

Purpose: Fungal keratitis is a serious eye infection that can cause irreversible vision loss. One of the causative fungal pathogens, Fusarium solani (Neocosmospora solani), shows limited susceptibility to antifungal drugs. Furthermore, differences between in vitro and clinical outcomes are encountered in some cases, complicating treatment. In this study, we compared in vitro and ex vivo antifungal susceptibility using a porcine corneal model of F. solani keratitis. Methods: An ex vivo fungal keratitis model was developed using porcine corneas, which were inoculated with F. solani and assigned to four treatment groups: natamycin (NAT), voriconazole (VRCZ), luliconazole (LLCZ), or saline (uninfected control). We compared the antifungal efficacy of each drug on day 2 to day 4 of fungal development. DNA was extracted from all corneas and used in real-time polymerase chain reaction to quantitatively assess fungal growth. Fungal morphology was examined by digital microscopy. Results: All antifungal treatment groups demonstrated antifungal activity. The NAT-treated group showed clear inhibition of fungal growth as well as fungal structural damage. The VRCZ-treated group exhibited growth inhibition; however, fungal growth persisted even after additional drug administration. The LLCZ-treated group not only suppressed fungal growth but also caused structural disruption of fungal cells after additional administration, suggesting a strong antifungal effect. Conclusions: We successfully established an ex vivo Fusarium keratitis model using porcine corneas, which enabled us to evaluate antifungal susceptibility by quantifying fungal growth and observing fungal morphological changes.