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Stephanie Wan, Matteo Metruccio, Abby Kroken, Melinda Grosser, David J Evans, Suzanne M J Fleiszig; Impact of contact lens wear and dry eye on the amicrobiomic status of the murine cornea. Invest. Ophthalmol. Vis. Sci. 2018;59(9):902.
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© ARVO (1962-2015); The Authors (2016-present)
Contrasting with the conjunctiva and other exposed body surfaces, the cornea does not host a stable bacterial population (amicrobiomic). Yet, the cornea and conjunctiva are not usually distinguished in ocular surface microbiome research. Additionally, commonly used sequencing technologies detect nucleic acid, not bacterial forms. Here, Fluorescence In-Situ Hybridization (FISH) with a universal bacterial 16S rRNA gene probe was used to visually determine if contact lens wear or dry eye disease facilitate exposure to environmental bacteria at the corneal surface.
Wild-type C57BL/6 mice were fitted with silicone-hydrogel contact lenses on one eye for up to 7 days then sacrificed. Lenses were removed, cut in half, with one half homogenized and cultured for viable bacteria, the other labeled with a FISH probe for the bacterial 16S rRNA gene ([Alexa488]-GCTGCCTCCCGTAGGAGT-[Alexa488] (Eurofins Genomics) prior to confocal imaging. In other experiments, mice were subjected to experimentally-induced dry-eye (EDE) using a dehumidified chamber and scopolamine HBr injection (0.1mL of 10mg/mL) for 3 times per day for 10 days. EDE induction was confirmed using a phenol red thread test. Mice were sacrificed and eyes enucleated for FISH-labeling and imaging.
Bacteria were cultured from 9 out of 10 contact lenses examined. Very few bacteria (~10 CFU/lens) were cultured after 1 day of wear, but numerous (~4900 to 41,000 CFU/lens) were cultured from lenses worn for 7 days. Some ocular surface discharge was observed after 7 days of lens wear but corneas remained clear. Corynebacterium and Coagulase-Negative Staphylococcus spp. were most commonly identified from the lenses. FISH showed many bacteria residing on the posterior lens surface closest to the cornea, and few on the anterior lens surface. For EDE corneas, FISH showed few bacteria (5.00 ± 5.00 bacteria/field of view), not significantly different from untreated controls (1.33 ± 0.67 bacteria/field of view) (P > 0.05, Mann-Whitney U-test). Corneas were clear, but with no ocular discharge.
Environmental bacteria can colonize the posterior surface of mouse contact lenses worn on an extended wear basis without corneal infection. Microbial forms are absent from mouse corneas with dry eye disease, suggesting the associated irritation/inflammation occurs without disruption to mechanisms that normally prevent bacterial colonization of the cornea.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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