Therapeutic efficacy of nitazoxanide on Acanthamoeba keratitis in an experimental model

Acanthamoeba keratitis (AK) is a serious sight-threatening infection caused by various species of the opportunistic protozoan Acanthamoeba, especially in contact lens wearers and immunocompromised people. The aim of the study was to assess the therapeutic efficacy of two topical nitazoxanide (NTZ) formulations in experimentally induced AK. Three groups of male New Zealand white rabbits were used: group (A): infected and received NTZ in suspension form; group (B): infected and received NTZ in liquid crystal forming system; and group (C): infected and received topical chlorhexidine 0.02 %. The right eyes of the animals served as their corresponding infected untreated control. The animals were infected by Acanthamoeba isolated from human cases of AK. The effects of treatment were assessed over 30 days through daily clinical evaluation; grading of AK; and parasitological and histopathological examination of corneal tissues. The present work revealed that after inducing keratitis, signs of infection appeared on day 3, and all groups showed similar infection rates before treatment began. Corneal opacity improved significantly in animals treated by NTZ liquid crystal form, especially by days 18-30 post-treatment, scoring therapeutic outcomes comparable or superior to the chlorhexidine-treated group and markedly better than the NTZ suspension-treated group. Histopathological assessment confirmed these findings, with the NTZ liquid crystal group exhibiting minimal inflammation and no detectable cysts, highlighting its potential as an effective alternative agent against Acanthamoeba. In conclusion, NTZ in its liquid crystal form showed promise as a potential therapy for AK. Further studies are needed to establish safety and efficacy of topical NTZ in humans and its possible use in combination with other amoebicidal agents.