In vitro Inhibition of Aspergillus and Fusarium Species with Erythrosin B, Eosin Y, and Rose Bengal Photodynamic Antimicrobial Therapy

Abstract

Purpose : Corneal infections caused by Aspergillus and Fusarium species are difficult to treat and current treatments have limited efficacy. Novel treatments, such as rose bengal (RB) photodynamic antimicrobial therapy (PDAT), have shown some success treating fungal keratitis, but other photosensitizers such as Erythrosin B (EB) and Eosin Y (EY) may have greater inhibitory activity. This study will compare the inhibitory effect of RB, EB, and EY PDAT against Aspergillus and Fusarium ocular strains.

Methods : Seven fungal strains (Aspergillus flavus (n = 1), Aspergillus fumigatus (n = 1), Aspergillus glaucus (n = 1), Aspergillus niger (n = 1), Fusarium oxysporum (n = 1), Fusarium solani (n = 2)) were isolated from patients with ocular infections and grown on Sabouraud-Dextrose agar plates. Organisms were prepared in solutions of 1x10E4 CFU/mL and mixed with photosensitizers of 0.1% concentration. Plates were separated into seven groups: (1) control (isolate only), (2) 0.1% EB, (3) 0.1% EB with green light, (4) 0.1% EY, (5) 0.1% EY with green light, (6) 0.1% RB, (7) 0.1% RB with green light. Green light irradiation was performed with a 518nm green LED array with a final energy density of 5.4 J/cm². Plates were incubated and photographed at 72 hours. Fungal growth was analyzed within the diameter of the light irradiation (47mm).

Results : All seven fungal isolates showed no inhibition to EB, EY, and RB without light (figure 1). Of the four Aspergillus spp. isolates, there was no growth inhibition with any of the photosensitizers with light. In both F. solani strains, all photosensitizers with light showed full inhibition within the irradiation zone, except for one surviving colony within the RB light group. For F. oxysporum, EB and RB with light showed partial inhibition and EY with light showed minimal inhibition.

Conclusions : EB, EY, and RB with light were effective against both F. solani strains. F. oxysporum showed less inhibition to all photosensitizers with light compared to F. solani. A. fumigatus showed a small inhibition zone with EB light and A. glaucus showed a small inhibition zone with RB light. Further exploration with increased photosensitizer concentration and fluence is warranted. The result shows the strain specific inhibitory effect of different photosensitizers.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1: Growth inhibition results from EB, EY, RB PDATs with and without green light.