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S. J. Spurr-Michaud, S. Heimer, P. Argueso, M. Gilmore, I. Gipson; Non-Encapsulated Streptococcus Pneumoniae Isolated From Patients With Epidemic Conjunctivitis Induces Release of the Ocular Surface Membrane Mucins. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2352.
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Membrane-associated mucins of the ocular surface glycocalyx are hypothesized to provide a barrier against bacterial invasion. Bacterial infections occur by entry through wounds that disrupt the mucin barrier (opportunistic pathogens) or possibly by removing the mucin barrier (virulent pathogens). The membrane-associated mucin MUC16 plays a role in barrier function at the ocular surface, as its knockdown in corneal epithelial cells facilitates pathogen adherence. The purpose of this study was to compare the effect of opportunistic and virulent bacterial exoproducts on MUC16 present on the ocular surface epithelium.
Immortalized human corneal-limbal and conjunctival epithelial cells grown for optimal mucin expression were co-cultured for 1 and 4 hours with exoproducts from clinical isolates of two opportunistic bacteria, Staphylococcus aureus ME015 (SA) and encapsulated Streptococcus pneumoniae IB-ME152 (SPE), or a pathogenic bacterium, non-encapsulated Streptococcus pneumoniae #168 (SPN), a clinical isolate from epidemic conjunctivitis patients. Controls were cells grown in culture medium alone. Lack of toxicity was confirmed using MTT. Culture medium supernatants were collected to measure amount of MUC16 released from the cell surface. MUC16 mRNA was analyzed by real-time PCR and released MUC16 by Western blot.
At both 1 and 4 hours of treatment exoproducts of SPN caused significantly greater release of MUC16 from both corneal and conjunctival cells than did exoproducts of SA or SPE, when compared to untreated controls. There were no significant changes in MUC16 mRNA levels in either cell line after 4 hours exposure to exoproducts of all three bacteria.
Non-encapsulated SPN, which causes epidemic conjunctivitis, is more capable of inducing release of MUC16 from ocular surface epithelia than are the opportunistic bacteria, SA and SPE. These data indicate that more virulent pathogens that do not require epithelial injury for entry can manipulate the mucin barrier to reach the epithelial surface.
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