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H. Zhu, A. Kumar, J. Ozkan, D. Wu, S. Masoudi, R. Bandara, M. Willcox, R. N. Borazjani; Bacterial Adhesion to Silicone Hydrogel Lenses. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3434.
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Silicone hydrogels are rapidly becoming the lens of choice world-wide. Whilst these lenses have achieved excellent oxygen delivery to the cornea, they are associated with adverse events during wear. Many of these adverse events are related to bacterial adhesion to the lenses. This study aimed, for the first time, to examine the level of bacterial adhesion to the currently available silicone hydrogel lenses.
The different silicone hydrogel lenses used in the study were made from lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A, senofilcon A, narafilcon A, comfilcon A, enfilcon A, and asmofilcon A. Three strains of Staphylococcus aureus (31, 38, ATCC 6538) and three strains of Pseudomonas aeruginosa (6206, 6294, GSU-3) were used. Bacteria were grown overnight in minimum media containing 3H-uridine and then resuspended in PBS to 1x107 CFU/mL. Lenses were washed in PBS and then incubated in 1mL bacterial suspension for 18h. After being washed in PBS three times, the number of total (radioactive) and viable (CFU) bacteria adhered on lens surfaces were estimated using standard techniques.
In general, trends for adhesion of test strains within genera to different lenses were consistent. For S. aureus, total adhesion to lenses ranged from 3x104 to 8x105 total cells/lens, and 3x103 to 8x105 viable cells/lens. Highest adhesion was to lotrafilcon A lenses, lowest adhesion was to asmofilcon A lenses (p<0.05). For P. aeruginosa, total adhesion to lenses ranged from 9x105 to 4x106 total cells/lens, and 8x105 to 3x106 viable cells/lens. Highest adhesion was to comfilcon A lenses, lowest adhesion was to balafilcon A lenses (p<0.05).
This study, for the first time, reports the level of adhesion of bacteria to nine commercially available silicone hydrogel polymers. P. aeruginosa adhered in higher numbers than S. aureus regardless of lens polymer type. Within a bacterial type, there were differences in adhesion to lens polymer types. Future studies will examine the effect of lens wear on bacterial adhesion to these lenses.
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