Promising in vitro effects of selected antiseptics against Acanthamoeba Polyphaga strain - the etiological agent of vision-threatening keratitis identified in polish patient

Abstract

Purpose: In the last decades, Acanthamoeba keratitis, the vision-threatening corneal infection is detected with increasing frequency in Poland. As the disease is difficult to treatdue to extremely high resistance of cysts to chemicals, agents of possible anti-amoebic activity are still tested. In this study, A. polyphagaisolate of T4 genotype from patient with complicated keratitis, a history of swimming in a lake, not using contact lensesand A. castellanii Neff strain were evaluated in terms of their in vitro susceptibility to selected antiseptics. Methods & Materials: Samples of the strains cultured under bacteria-free conditions in BSC calf serum-enriched culture mediumwere exposed to antimicrobial agent Povidone-iodine and Aerodesin disinfectant. Effects of the compounds on Acanthamoeba strains following 48, 96 and 120 hrs exposure compared to the control cultures were monitored: the developmental form dynamics, encystation process, overall number of surviving amoebae, changes in cysts/trophozoites/proportion assessed in the exponential growth phase were determined. Results: The diagnosis was confirmed by confocal microscopy, in vitro culture and by 18S rDNA gene sequences (T4 genotype). Both antiseptics showed some amoebostatic effects on Acanthamoeba strains. Povidone iodine after 120 h from application reduced number of viable amoebae to 17% in comparison to the control samples (100%); Aerodesin indicated expected cysticidal efficacy: no amoebae after 92 h exposure were detected. Conclusion: Risk factors of Acanthamoeba keratitis diagnosed mainly in contact lens wearers include also ocular exposure to water containing cysts and trophozoites of the amphizoic amoebae. Promising in vitro effects of the chemicals against A. polyphaga strain, etiological agent of vision-threatening keratitis justifies further tests with a modified agent application pattern particularly in term of expected cysticidal efficacy.