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Y. T. Wu, H. Zhu, M. Willcox, F. Stapleton; Microbial Contamination and Biofilm on Contact Lens Storage Cases. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5649.
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Poor contact lens storage case hygiene is a risk factor for microbial keratitis. The aims of this study were to detect case contamination by routine microbiological culturing and biofilm staining, and to evaluate the two different sampling methods.
Twenty-seven contact lens storage cases were collected from asymptomatic contact lens wearers. One of the wells was sampled for routine microbial analysis using a calcium alginate swab at two different positions. The first sample was collected from the upper inner rim of the well, and the second from the bottom of the well. Both samples were cultured on chocolate agar under anaerobic and microaerophilic conditions; Colonies (CFU) were counted and identified using standard biochemical techniques. The second well of the case was stained with crystal violet to visualise biofilm, the stain was then extracted with ethanol and absorbance measured at 595 nm.
The age of lens storage case ranged from two weeks to one year. Both contamination rate and average CFU were higher for swabs taken at the upper inner rim than the swabs taken at the bottom of the well (P<0.05). The most frequent micro-organisms recovered from both groups of samples were Bacillus. The biofilm staining was most significant at the meniscus of the solution. Interim analysis showed neither association between the biofilm density and the number of organisms recovered nor between density and case age (p > 0.05).
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