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E. B. Hume, S. Khan, N. Cole, M. Willcox; Investigating Specific Virulence Factors Involved in Staphylococcus aureus Keratitis. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3457.
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We have demonstrated differences in the proteome of a virulent clinical isolate and an avirulent laboratory strain 8325-4 and identified possible virulence factors: fibronectin binding protein (Fnbp), extracellular adherence protein (Eap), and staphopain. We investigated the role of these virulence factors in the pathogenesis of microbial keratitis using a range of mutant strains and inhibitors to these proteins.
To ascertain the effect of Fnbp and Eap on S. aureus pathogenesis, strains (Staph 38, NCTC 8325-4, ΔFnbpA , ΔFnbpB, ΔFnbpAB, FnBpA+, Fnbp B+, Newman, ΔEap) were used in in vitro bacterial invasion of cells and corneal infections in mice. For the effect of staphopain, inhibition was achieved by the addition of staphostatin prior to cellular invasion and corneal infection in mice. Clinical scores, PMNs and bacterial numbers were determined.
All Fnbp and Eap mutants showed significant reduction in, the ability to invade corneal epithelial cells. In the animal model FnbpB and double mutant FnbpAB demonstrated reduced clinical scores, PMNs and bacterial numbers. There was no significant reduction in clinical scores, bacterial numbers or PMNs for the FnbpA mutant. Corneal infection with Eap mutants resulted in reduced bacterial numbers and clinical scores. Inhibition of staphopain also significantly reduced both bacterial numbers and clinical scores.
These results show that the FnbpB, Eap and staphopain are important in the colonization of the cornea by S. aureus but not FnbpA .
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