Effect of photodynamic therapy with methylene blue on Acanthamoeba in vitro.
OBJECTIVE
To evaluate the disinfectant effect of methylene blue (MB)-mediated photodynamic therapy (PDT) on a pathogenic strain of Acanthamoeba.


METHODS
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/cm(2) 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.


RESULTS
MB-PDT suppressed the respiratory activity of trophozoites in an MB-concentration-dependent manner at total light doses of 10.8 J/cm(2). 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.


CONCLUSIONS
MB-PDT is effective against Acanthamoeba in vitro and has synergistic effects with PHMB and amphotericin B.
department of Ophthalmology, Ehime University Graduate School of Medicine, Ehime, Japan.
Tsuyoshi
T
Mito
Takashi
T
Suzuki
Takeshi
T
Kobayashi
Xiaodong
X
Zheng
Yasuhito
Y
Hayashi
Atsushi
A
Shiraishi
Yuichi
Y
Ohashi
D048248:Acanthamoeba castellanii / Q000187:drug effects* / Q000254:growth & development*; D000562:Amebiasis / Q000188:drug therapy; D000563:Amebicides / Q000494:pharmacology; D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D000935:Antifungal Agents / Q000494:pharmacology; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007634:Keratitis / Q000188:drug therapy / Q000469:parasitology; D008751:Methylene Blue / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology; D011108:Polymers / Q000494:pharmacology; D011743:Pyrimidines / Q000494:pharmacology; D012256:Riboflavin / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D014467:Ultraviolet Therapy / Q000379:methods; D065819:Voriconazole
D000563:Amebicides; D000935:Antifungal Agents; D004791:Enzyme Inhibitors; D006146:Guanidines; D017319:Photosensitizing Agents; D011108:Polymers; D011743:Pyrimidines; D014230:Triazoles; C107145:poly(hexamethylenebiguanidinium); D000666:Amphotericin B; D065819:Voriconazole; D008751:Methylene Blue; D012256:Riboflavin