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T. Suzuki, J. G. Swoboda, S. Walker, M. S. Gilmore; Targeting Wall Teichoic Acids Byosynthesis in Ocular Infection. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2398.
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Wall teichoic acids (WTAs) are major polyanionic polymers in the cell wall of Staphylococcus aureus. However, little is known about a role of WTAs in ocular infection such as keratitis and endophthalmitis. This study was designed to investigate the possible contribution of WTAs using in vitro and in vivo model.
The strains used were S. aureus parental strains (RN6390 and RN4220) and their isogenic S. aureus mutants defective in WTAs biosynthesis because of mutation in the tarO gene (RN6390ΔtarO and RN4220ΔtarO). To determine the role of WTAs in adhesion and invasion in vitro, RN4220 or RN4220ΔtarO (108CFU/ml) were exposed to human cultured corneal epithelial cells (HCEC) for 1 h. Monolayers were washed to remove unbound bacteria, and bacterial adhesion and internalization was quantified. To determine the role of WTAs in the pathogenesis of infection, either RN6390 or RN6390ΔtarO (2500CFU) was inoculated into the vitreous chamber of C57B6 mice. Changes in electroretinography (ERG), histopathology, and numbers of organisms were determined and compared throughout the infection.
In vitro, WTAs-deficient S. aureus were defective in attachment and invasion of HCEC cells by more than 80%. In vivo, endophthalmitis caused by the parental strain RN6390 resulted in a significantly greater reduction of B-wave amplitude of ERG than RN6390ΔtarO. Histological examination showed that the retina was profoundly destroyed in the eyes infected with RN6390 but not eyes infected with RN6390ΔtarO.
WTAs are important for the full manifestation of virulence by S. aureus in ocular infection. Part of the attenuation appears to relate to changes in adherence and invasion.
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