Photodynamic antimicrobial therapy with Erythrosin B, Eosin Y, and Rose Bengal for the inhibition of fungal keratitis isolates: An in vitro study.

Introduction: Fungal keratitis is a leading cause of corneal blindness, with current antifungal treatments having limited efficacy. One promising treatment modality is Rose Bengal (RB) photodynamic antimicrobial therapy (PDAT) that has shown mixed success against fungal keratitis. Therefore, there is a need to explore the antimicrobial efficacy of other green-light activated photosensitizers that have deep penetration in the cornea to combat the deep fungal infections, such as Erythrosin B (EB) and Eosin Y (EY).

Objective: This study will explore PDAT inhibitory effects with different photosensitizers, RB, EB, and EY against two common fungal ocular isolates, Aspergillus spp. and Fusarium spp.

Methods: Twelve fungal isolates (Fusarium spp., n = 6, Aspergillus spp., n = 6) were prepared in suspension for evaluation of growth inhibition to PDAT with three photosensitizers, EB, EY, and RB. Custom green light source (λ = 518 nm, energy density = 5.4 J/cm) was applied to the experimental groups for 15 min. Fungal growth inhibition was assessed after experimentation by analyzing the area of growth within the irradiated zone on agar plates.

Results: All twelve fungal isolates showed no inhibition to EB, EY, and RB without irradiation. Fusarium spp. were more susceptible to PDAT than Aspergillus spp. In all Fusarium solani strains, all photosensitizers with light showed full inhibition within the 47 mm diameter irradiation zone.

Conclusion: EB, EY, and RB PDAT demonstrated comparable antifungal inhibition against six Fusarium ocular isolates; these findings in conjunction with the deeper tissue penetration of EB and EY, are of interest to treat more advanced and deeper cases of fungal keratitis.