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T.A. Hannan, W.D. Mathers; Acanthamoeba Sensitivity Testing Results for Various Amoebacidal Medications and Concentrations . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4766.
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Purpose: Treatment of Acanthamoeba keratitis with various topical medications is not based on assessment of the infecting organisms sensitivity to known anti-amoeba medications since no method of testing this sensitivity exists. We have devised a method to evaluate the effectiveness of various topical medications currently in use. Our approach is directed toward assessing the sensitivity of Acanthamoeba cysts which are much more resistant to treatment than trophozoites. Methods: We tested cysts of seven Acanthamoeba organisms taken from patients with AK. The cysts were subjected to solutions of Chlorhexidine, PHMB at 0.02% and 0.04% and Clotrimazole at 1.0% concentration diluted to one-third for 5 minutes and then diluted 100 fold to mimic topical application concentrations. Results: We found primarily the concentration of the solutions and secondarily the type of drug was more important than the virulence of the organism. Both chlorhexidine and PHMB at 0.04% concentration were significantly more effective than the 0.02% solutions. Most organisms displayed a similar sensitivity pattern. Conclusions: We have devised a method of testing Acanthamoeba cysts that may be helpful in assessing clinical efficacy of anti-amoeba medications at variable concentrations. Clinical application of this information appears promising and will continue to be assessed. We welcome additional organisms to evaluate.
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