Optometry Research Today is a free monthly online journal that collates and summarizes the latest research about Optometry, including details on myopia, optometric practice, therapy. | ||||||||
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The Impact of Inoculation Parameters on the Pathogenesis of Contact Lens Related Infectious Keratitis.Tam C, Mun J, Evans DJ, Fleiszig SM School of Optometry, University of California at Berkeley, Berkeley, United States. PURPOSE. Contact lens wear predisposes to Pseudomonas aeruginosa keratitis, but the mechanisms involved remain unclear. We used an in vivo model to study lens inoculation conditions enabling disease. METHODS. Custom-made hydrogel contact lenses were fitted to rats after incubation in P. aeruginosa ~10(11) cfu/ml (3 h) or ~10(3) cfu/ml (24 h). Another group was inadvertently inoculated with a suction-pen previously used with high inocula, but ethanol-rinsed and dry-stored (6 months). Some corneas were tissue paper-blotted to cause fluorescein staining before lens fitting. Contralateral eyes were untreated. 24 h after detecting disease, lenses were transferred to naïve rats or examined by confocal microscopy before homogenization to quantify viable bacteria. After lens removal corneas were washed to collect non-adherent bacteria and analyzed by immunohistochemistry. RESULTS. All eyes challenged with unworn contaminated lenses developed keratitis after ~7-10 days. Disease delay and severity were unaffected by inoculum parameters or tissue-blotting, but pathology occurred sooner with lenses transferred from infected eyes (~2 days). Worn lenses and corneal washes contained infecting bacteria. Posterior, not anterior, lens surfaces harbored P. aeruginosa biofilms that penetrated the lens matrix. Diseased corneas showed an infiltration of phagocytes and T-lymphocytes. CONCLUSIONS. P. aeruginosa induces keratitis in this lens-wearing model after a single inoculation. Delayed disease onset was interesting considering the greater keratitis risk in people during extended wear. Infection did not require disruption of corneal barrier function before lens wear and occurred without exposure to lens care solutions. The data suggest that keratitis involves biofilm formation or other bacterial adaptations in vivo. Published 4 February 2010 in Invest Ophthalmol Vis Sci.
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