Acanthamoeba polyphaga are free-living amoebae that can be considered potentially pathogenic organisms by cause
serious human infections, including keratitis and granulomatous amoebic encephalitis that usually results in death.
Photodynamic inactivation (PDI) has been used for the biological control of microorganisms and can be promise in the
control of Acanthamoeba infections. This study evaluated the in vitro effectiveness of PDI in A. polyphaga using
curcuminoids salt as photosensitizer (PS) besides observing morphological changes caused by this PS in this organism,
in confocal microscopy. A. polyphaga trophozoites were grown at 37°C in PYG medium for 48 to 72 hours. After, the
trophozoites were incubated with PS solution during one hour and the samples were irradiated using light-emitting
diodes at 460 nm at light doses 30 and 50 J/cm2. The results revealed reduction of 27.7%, 61.4% and 82.5% at 30 J/cm2
and 75.2%, 85.0% and 95.9% at 50 J/cm2, respectively, at curcuminoid salt concentrations of 500, 1000 and 1500
μg/mL. Through fluorescence images, it was possible to visualize the curcuminoid salt’s uptake by the trophozoites. The
PS showed toxicity to amoebae, in the dark, but the irradiation in PDI contributed to amoebae death effect. These data
suggest that PDI may be an application of therapeutic intervention against Acanthamoeba infections, since it was
effective in the inactivation of these amoebae.