Ocular Microbiology and Immunology Group
Back to OMIG Main Page

< Previous | 2025 Agenda and Abstracts | Next >

2025 OMIG Abstract

Activity of Photoactivated Rose Bengal Alone or Combined yo Standard Treatments in Trophozoites and Cysts of Acanthamoeba: In vitro Study

Talita Trevizani Rocchetti, Larissa Fagundes Pinto, Camila Kase, Aileen Miwa Tabuse, Maria Cecilia Zorat Yu, Jennifer Rose Nussbaumer, Denise de Freitas, Ana Luisa Hofling-Lima

Department of Ophthalmology and Visual Sciences, Escola Paulista de Medicina–Federal University of São Paulo, São Paulo – Brazil

Purpose: To evaluate the in vitro efficacy of photoactivated 0.1% Rose Bengal by green light (5.4J/cm2) (RB-PDT) in combination with moxifloxacin (MOX), 0.15% Anfotericin B (AnfoB); 0.02% polyhexamethyl biguanide (PHMB) with/without benzalkonium chloride (BAK) and propamidine isethionate (PI) in Acanthamoeba trophozoites (AT) and cysts (AC).

Methods: AT were exposed to RB-PDT alone or combined with MOX; AnfoB; PHMB and BAK; PHMB; PHMB and PI. AC (in three different mature stages, 3, 7, 14 days encystment), were exposed to RB-PDT alone or combined with PHMB and BAK; PHMB; PHMB and PI. Acanthamoeba death rate (ADR) was assessed by fluorescence microscopy on the Incell® microscope and cells counted by Image J software. Statistical analyses were performed by ANOVA and Poisson (p<0.05).

Results: The RB-PDT reduced the number of cells of AT significantly (p<0.001) and presented 80% ADR in AT. In AC RB-PDT ADR was 50% and decreased significantly when AC was getting mature, 14 days encystment (23%) (p<0.001). The RB-PDT alone or combined with MOX or AnfoB presented similar ADR (p<0.001) to AT. The PHMB ADR increased when combined to RB-PDT (p<0.001) in AT and AC, however ADR did not improve when PHMB and RB-PDT were combined simultaneously with BAK and/or PI.

Conclusions: RB-PDT has good activity in AT death and improved the activity of anti-amebic treatment with 0.02% PHMB in AT and AC. However, RB-PDT activity decreased when the cysts were mature, suggesting the use of RB-PDT at the beginning of Acanthamoeba infection.