Acanthamoeba keratitis--resistance to medical therapy

Successful medical therapy of Acanthamoeba keratitis has been reported with combination therapy; topical Brolene and neomycin. Resistance has not so far been identified as a problem, but was the basis for recurrent disease observed in a patient with bilateral infection. Eradication of amoebae was finally achieved following prolonged topical therapy and two corneal grafts in each eye. Topical anti-amoebic therapy with paromomycin, benzethonium chloride, clotrimazole and R11/29 (a phenanthridinium compound), was continued for three months post-operatively. No further recurrences occurred during 14 months' follow-up. Drug sensitivities were performed for three isolates of Acanthamoeba sp (group II) which demonstrated the development of resistance to Brolene and arsenic. In addition, the resistant isolates were temperature-sensitive mutants which would not grow at temperatures above 30 degrees C. This could explain 'culture-negative' results in some cases of clinical recurrence when incubation of laboratory samples had only been performed at 37 degrees C.