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S. L. Buck, R. L. Smith, B. A. Schlech; Methodology for the Evaluation of a Contact Lens Disinfecting Solution Against Acanthamoeba . Invest. Ophthalmol. Vis. Sci. 2008;49(13):4871. doi: https://doi.org/.
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There are no standardized methods for evaluating contact lens solutions against Acanthamoeba. A recent increase in Acanthamoeba keratitis infections, traced back to a PHMB preserved contact lens solution, has warranted a need for looking at standardized methods for the evaulation of contact lens solutions against Acanthamoeba. In this study we evaluated the activity of a contact lens solution against Acanthamoeba using methodology based on the FDA, ANSI and ISO Stand Alone and Regimen tests for bacteria and fungi with modifications for working with Acanthamoeba.
OPTI-FREE® RepleniSH® Multi-Purpose Disinfecting Solution (RepleniSH®), a "no rub" disinfecting solution for contact lenses, with POLYQUAD® and ALDOX® preservatives, was challenged with cysts and trophozoites (trophs) of A. castellanii ATCC 30234 and A. polyphaga ATCC 30871. The cyst is the more resistant form of the organism and was used in the Stand Alone test. Cysts and trophs were used in the Regimen test. Three lots of RepleniSH® were evaluated in the presence of organic soil. In the Stand Alone test, a volume of RepleniSH® was inoculated with the challenge organism, an aliquot was removed at the disinfection time, diluted and plated using a quantitative mirotitre plate method. In the Regimen test, silicone hydrogel lenses were inoculated with the challenge organism, the no rub regimen was performed and each lens was placed in a lens case containing about 4 mL of test solution. At the disinfection time each lens and a sample of the lens case solution were diluted in microtitre plates. Viable organisms were recovered with E.coli ATCC 8739. Plates were observed for viable amoeba after 14 days with an inverted microscope and survivors were enumerated.
These methods showed a reliable and objective way to evaluate lens solutions against Acanthamoeba. Stand Alone test results showed a 2.0 ± 0.3 and 1.6 ± 0.7 log reduction for A. castellanii and A. polyphaga cysts respectively at the disinfection time. The regimen test results showed no survivors for 95% of the lenses. Fewer than 10 survivors per lens were observed for the remaining lenses.
Currently there are no standardized methods for evaluating lens care solutions against Acanthamoeba. Using methods based on the FDA, ANSI and ISO guidelines for bacteria and fungi this study demonstrated objective, consistent and reliable methods for evaluating contact lens solutions against Acanthamoeba. In this study RepleniSH® Multi-Purpose Disinfecting Solution showed antimicrobial activity against Acanthamoeba and the "no rub" regimen effectively removed trophs and cysts from silicone hydrogel lenses.
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