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Taiichiro Chikama, Kentaro Sueoka, Ji-Ae Ko, Yoshiaki Kiuchi, Takemasa Sakaguchi, Akira Obana; Antimicrobial efficacy of photodynamic therapy with TONS504 against pathogenic filamentous fungi. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3887.
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© ARVO (1962-2015); The Authors (2016-present)
Infectious keratitis is a sight-threatening condition. We previously demonstrated an antimicrobial effect of photodynamic antimicrobial chemotherapy (PACT) with a new photosensitizer, TONS504, with regard to various types of microorganism, including Candida albicans (a yeast-type fungus), that are responsible for infectious keratitis. We have now evaluated the effectiveness of PACT with TONS504 against the filamentous fungi Fusarium solani and Aspergillus fumigatus.
PACT was performed with the cationic chlorine derivative TONS504 (Porphyrin Lab, Okayama, Japan) and a light-emitting diode (LED) device (CCS, Kyoto, Japan) that delivers light at a single wavelength (660 nm). It was applied to F. solani or A. fumigatus at 500 and 750 colony-forming units (CFU), respectively. The fungi were exposed to TONS504 at a concentration of 10 µg/mL in the absence or presence of 20 mM EDTA, irradiated at a light energy of 30 J/cm2, and cultured on potato dextrose agar in a 10-cm dish at 25°C for 4 days in the dark for evaluation of colony formation.
PACT with TONS504 inhibited the growth of F. solani by 88%, and this inhibitory effect was increased to 97% in the presence of EDTA. In contrast, TONS504-PACT did not affect colony formation by A. fumigatus in the absence or presence of EDTA. The growth of neither fungus was affected by TONS504 in the absence of irradiation or by irradiation in the absence of TONS504.
TONS504-PACT inhibited the growth of F. solani, a cause of infectious keratitis, and this effect was enhanced by EDTA. The difference in the efficacy of TONS504-PACT between F. solani and A. fumigatus may arise from structural differences in the cell wall of these two fungi. Further studies are warranted to understand differences in the effectiveness of TONS504-PACT against various strains of fungi and to optimize its antimicrobial efficiency.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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