DRUG-RESISTANCE AND ACANTHAMOEBA-KERATITIS - THE QUEST FOR ALTERNATIVE ANTIPROTOZOAL CHEMOTHERAPY

Trophozoites and cysts of 20 isolates of Acanthamoeba from the cornea and five from related samples were tested in vitro for sensitivity to ten drugs (three aromatic diamidines, two aminoglycosides, two macroli des, a polyene macrolide antibiotic, an organoarsenical and an antimet abolite) and two cationic antiseptics (chlorhexidine and polyhexamethy lene biguanide, PHMB). Only chlorhexidine and PHMB showed uniform amoe bacidal activity. Aromatic diamidines (pentamidine isethionate, propam idine isethionate and diminazene aceturate) generally proved effective against both forms of the amoeba; only pentamidine gave synergy with the biguanide while propamidine gave an additive effect. Other drugs t ested proved erratic or ineffective against different isolates. Chlorh exidine alone, or together with propamidine, was subsequently used in two patients with proven Acanthamoeba keratitis; the causative isolate s were sensitive to the individual compounds and to the combination in vitro. The treatment provided resolution of the clinical disease; amo ebae were shown to be nonviable by histology and culture. The combinat ion of chlorhexidine and propamidine is recommended for treatment of p roven Acanthamoeba keratitis.