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J. Dantam, H. Zhu, F. Stapleton; Biocidal Efficacy of Silver Impregnated Contact Lens Storage Cases in vitro. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1541.
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© ARVO (1962-2015); The Authors (2016-present)
Silver-impregnated contact lens (CL) storage cases aim to reduce microbial contamination of storage cases during the use, however there are limited data on their effectiveness. This study evaluated anti-microbial activity of silver-impregnated CL cases and silver release characteristics in these storage cases in-vitro.
Three silver-impregnated CL storage cases MicroblockTM (CIBA Vision Corporation), i-clean® (Sauflon Pharmaceuticals Ltd), Nano-case® (Marietta Vision, Inc.) were evaluated. The test organisms included the ISO14729 panel Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 9027, Serratia marcescens ATCC 13880, Candida albicans ATCC 10231, Fusarium solani ATCC 36031and two clinical isolates, Delftia acidovorans and Stenotrophomonas maltophilia. Each well of the storage case was challenged with 2mL of the test organism in phosphate buffered saline (PBS) at 103, 104, 105 and 106 CFU/mL. Aliquot were removed at specific time intervals of 6, 10 and 24h incubation at 25°C and colony forming units of challenge microorganisms were enumerated. At similar incubation conditions, each well of the lens cases was filled with 3mL of Dulbecco’s PBS for the quantification of the release of silver ions and the samples were analysed using Inductively Coupled Plasma Mass Spectrometry.
Significant differences in antimicrobial activity were observed between the cases only at 24h. MicroblockTM showed the highest activity against P. aeruginosa, S. marcescens, D. acidovorans and F. solani, for all inocula (p ≤ 0.001). i-clean® was most effective against S. aureus (p ≤ 0.007), whereas Nano-case® showed greatest (p < 0.02) activity against S. maltophilia. MicroblockTM released 45 ± 12 µg/L of silver at 24h, however there was no detectable silver release for i-clean® and Nano-case®.
Current silver-impregnated CL storage cases show variation in their in vitro activity. Broadly, the MicroblockTM case demonstrated robust activity against most Gram-negative bacteria which is consistent with the pattern of silver release, while the i-clean® case was more effective against S. aureus. Also, the silver release data suggest different modes of action for different cases.
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