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Tsuyoshi Mito, Takashi Suzuki, Takeshi Kobayashi, Xiaodong Zheng, Yasuhito Hayashi, Atsushi Shiraishi, Yuichi Ohashi; Effect of Photodynamic Therapy with Methylene Blue on Acanthamoeba In Vitro. Invest. Ophthalmol. Vis. Sci. 2012;53(10):6305-6313. doi: https://doi.org/10.1167/iovs.12-9828.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the disinfectant effect of methylene blue (MB)–mediated photodynamic therapy (PDT) on a pathogenic strain of Acanthamoeba.
Acanthamoeba castellanii (ATCC 50370) used in this study were treated under one of four experimental conditions: light irradiation and incubation in MB (L+M+), light irradiation and incubation in physiologic solution (L+M−), incubation in MB only (L−M+), and incubation in physiologic solution (L−M−). M+ trophozoites were incubated in either 0.25 or 0.5 mM MB for 10 minutes. L+ organisms were irradiated for 30 minutes following incubation in solution. A halogen lamp (660 ± 10 nm) with a maximum output of 6 mW/cm2 was used as the PDT light source. After treatment, antiacanthamoeba activity was evaluated by checking the respiratory activity of the amoeba with 5-cyano-2,3-tetrazolium chloride (CTC) staining. We also determined whether the effect of PDT with MB had been retained or augmented when it was performed in combination with conventional antiamoebic agents.
MB-PDT suppressed the respiratory activity of trophozoites in an MB-concentration–dependent manner at total light doses of 10.8 J/cm2. The respiratory activity of each group as a percentage of that of L−M− is as follows: L+M+ 11.6% (0.5 mM), 60.9% (0.25 mM); L−M+ 116.5% (0.5 mM), 105.5% (0.25 mM); L+M− 107.6%; and L−M− 106.3%. (L+M+ versus L−M− P < 0.05). MB-PDT had a synergistic effect when used in combination with polyhexamethylene biguanide (PHMB) or amphotericin B, but not with voriconazole.
MB-PDT is effective against Acanthamoeba in vitro and has synergistic effects with PHMB and amphotericin B.
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