Antifungal efficacy of photodynamic therapy with TONS 504 for pathogenic filamentous fungi

Abstract

The pathogenic filamentous fungi Fusarium solani (F. solani) and Aspergillus fumigatus (A. fumigatus) are common causes of fungal keratitis. We have here evaluated the antifungal efficacy of photodynamic antimicrobial chemotherapy (PACT) with the novel chlorin derivative TONS 504 and a light-emitting diode (LED) with a wavelength of 660 nm for these fungal species. Isolated fungal spores were irradiated at LED energies of 10, 20, or 30 J/cm² in the presence of TONS 504 at concentrations of 1 or 10 mg/L. As a control, spores were exposed to TONS 504 or LED radiation alone. The treated spores were then cultured on potato dextrose agar plates at 25 °C for 3 to 4 days before determination of colony formation as a measure of viability. Fungal growth was inhibited in a manner dependent on both LED energy and TONS 504 concentration. The inhibitory effect on F. solani was complete with TONS 504 at a concentration of 1 mg/L and LED irradiation at 30 J/cm² as well as at a TONS 504 concentration of 10 mg/L and LED irradiation at 10, 20, or 30 J/cm². In contrast, that on A. fumigatus was only partial at a TONS 504 concentration of 10 mg/L and LED irradiation at 20 or 30 J/cm². The antifungal effect of PACT on A. fumigatus was thus inferior to that on F. solani. PACT with TONS 504 and an LED thus warrants further evaluation with regard to its potential effectiveness for the treatment of infectious fungal keratitis.

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