Acanthamoeba keratitis: a sobering case and a promising new treatment

This case report describing Acanthamoeba keratitis in a 41-year-old male disposable contact lens wearer, adds some sobering and some encouraging information for the future management of this infection. Initial treatment with topical propamidine isethionate (Brolene) and polymyxin B/neomycin/ gramicidin (Neosporin) led to an unsatisfactory clinical response. Topical miconazole 1%, prednisolone acetate 0.12% and oral itraconazole were then added to his treatment. This was later discontinued on noticing ipsilateral toxic cataract formation and an unresponsive pupil. The above medications were replaced with topical polyhexamethylene biguanide (PHMB) 0.02%, which we had shown to have superior in-vitro amoebicidal activity when compared to the other antiamoebic agents used in this case. Withdrawal of the multitreatment schedule and commencement of PHMB was associated with resolution of his keratitis, healing of a large epithelial defect and settling of severe conjunctivitis. The identical Acanthamoeba strain was isolated from the patient's contact lens storage case and cornea, possibly implicating the contaminated contact lens case in the aetiology of his keratitis. This is the first Australasian experience using PHMB to treat Acanthamoeba keratitis. It appears to be a promising new treatment for this infection.