Salicylate inhibition of Acanthamoeba attachment, to contact lenses - A model to reduce risk of infection

Purpose: Acanthamoeba attachment (adsorption) to hydrogel contact lenses is enhanced by Pseudomonas aeruginosa biofilm, The effect of sodium salicylat e on Acanthamoeba attachment to biofilm-coated and uncoated hydrogel lenses was investigated. Design: Experimental study. Participants and Controls: A minimum of 16 replicates were used for each te st condition; a control condition using clean lenses without biofilm was in cluded. Methods: Four groups of hydrogel contact lenses (etafilcon A) were pretreat ed with P. aeruginosa to form a biofilm, In addition, two more groups remai ned untreated. Quartered lenses of all six groups were then incubated in a suspension of A. castellanii trophozoites. Two batches of lenses had either 3 or 30 mM sodium salicylate added to the bacterial suspension (stage 1 in tervention), Two other batches of lenses had salicylate added to the amoeba l suspension (stage 2 intervention). One of the batches, which had a stage 1 intervention, had salicylate added at the second stage as well. The remai ning batches received no salicylate exposure and included lenses with and w ithout biofilm coating. Main Outcome Measure: The outcome measure in this study was the number of A canthamoeba trophozoites attached, per square centimeter, to the hydrogel s urfaces. Results: Biofilm coating from P. aeruginosa gave a significantly increased attachment of A. castellanii trophozoites to the contact lens. When introdu ced at a first (biofilm) stage, second (trophozoite attachment) stage, or w ith intervention at both stages, 30 mM sodium salicylate reduced amoebal at tachment to the hydrogel lens. When applied to both stages and when applied at stage 2 to the biofilm coated contact lenses, 3 mM sodium salicylate re duced amoebal attachment. The 3 mM concentration was not effective for the lower level of amoebae attachment to uncoated (nonbiofilm) lenses. Conclusions: Sodium salicylate successfully reduced amoebal trophozoite att achment to hydrogel lenses. This was the result of one of the following pos sibilities or a combination thereof: inhibition of biofilm formation; a dir ect effect on the amoebae; an alteration in the biofilm-amoebal attachment and resulting modification of the hydrogel lens surface. The results of thi s study suggest the major action is at stage 2 (on amoebal attachment to le nses) and favors alteration of the biofilm-amoebal attachment mechanism, Th is study demonstrates salicylate's potential benefit as a component of cont act lens care solutions, designed to reduce microbial attachment and the ri sk of infection. Ophthalmology 2000;107:112-117 (C) 2000 by the American Ac ademy of Ophthalmology.