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T. K. Beattie, A. Tomlinson, D. V. Seal; Reducing Acanthamoeba Attachment to Hydrogel Contact Lenses - What is the Minimum Effective Concentration of Sodium Salicylate?. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1531.
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© ARVO (1962-2015); The Authors (2016-present)
The ubiquitous nature of the opportunistic protozoa Acanthamoeba means that ocular infection with this organism is difficult to eradicate. Producing an effective amoebacidal lens care solution has proven challenging. One approach however may be to reduce amoeba attachment to lenses in the first place. Sodium salicylate at a concentration of 30mM successfully reduces Acanthamoeba trophozoite attachment to clean hydrogel contact lenses, while a concentration of 3mM is ineffectual. This study was undertaken to determine the minimum effective concentration of salicylate with regard to reducing acanthamoebal attachment.
Unworn Acuvue hydrogel (etafilcon A) contact lens quarters were incubated individually for 90 minutes in suspensions of plate-cultured Acanthamoeba castellanii trophozoites containing 0, 10, 15, or 20mM sodium salicylate. After incubation trophozoites attached to one surface of each quarter were counted by direct light microscopy. Sixteen replicates were examined for each concentration. Logarithmic transformation of the data allowed the use of parametric statistical analysis. Analysis of variance was used to analyse the transformed data at the 5% level of significance. Subsequent follow up two-sample t tests with Bonferroni’s error factor for multiple computations were applied.
A significant difference was detected between quarters not exposed to salicylate and those with salicylate present in the amoebal suspension (ANOVA, P<0.0001); a slight significant difference was detected between the dosages (ANOVA, P<0.046). Application of 10mM salicylate did not produce a significant reduction in amoebal attachment (t test, P=0.045), whereas application of 15mM (t test, P=0.0042) or 20mM (t test, P=0.005) of salicylate did significantly reduction amoebal numbers.
Under the test conditions the minimum effective concentration of salicylate found to reduce ameobal attachment to clean lenses was 15mM. Possible modes of action include direct effect on the amoebae and/or modification of the surface of the hydrogel lens. This study highlights the potential of salicylate as a component of contact lens care solutions, designed to reduce not only Acanthamoeba attachment, but potentially other micro-organisms, with the aim of reducing the risk of ocular infection.
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