Photosensitized inactivation of Acanthamoeba palestinensis in the cystic stage

Abstract

To develop alternative approaches for medical and environmental control of pathogenic Acanthamoeba spp. by means of photodynamic treatment with a tetracationic Zn(II)-phthalocyanine (RLP068). Incubation of cyst cultures with RLP068 for 1 h caused an accumulation of readily detectable concentrations of the phthalocyanine, even at doses as low as 0.5 micromol l(-1). RLP068 exhibited no dark toxicity towards cysts up to 5 micromol l(-1) concentration. A decrease of c. 50% in cyst survival in comparison with controls was measured upon incubation of the cysts with 0.5 micromol l(-1) RLP068, followed by exposure to light (600-700 nm) for 20 min at a fluence rate of 50 mW cm(-2) (60 J cm(-2)). After incubation with 3 and 5 micromol l(-1) RLP068 and irradiation, the cysts lost their excystment ability as early as day 5 and up to day 10, and were clearly damaged when observed under an interference contrast microscope. These data indicate the promising use of RLP068 in phototreatment of diseases caused by pathogenic amoebae and in initial disinfection of wastewaters. Rapid and extensive photodamage may be induced in the highly resistant cystic stages by means of 600- to 700-nm light sources.