Surface proteins that promote adherence of Staphylococcus aureus to human desquamated nasal epithelial cells

Abstract

Background: The natural habitat of Staphylococcus aureus is the moist squamous epithelium in the anterior nares. About 20% of the human population carry S. aureus permanently in their noses and another 60% of individuals are inte rmittent carriers. The ability of S. aureus to colonize the nasal epithelium is in part due to expression of surf ace proteins clumping factor B (ClfB) and the iron- regulated surface determinant A (I sdA), which promote adhesion to desquamated epithelial cells present in the anterior part of the nasal vestibule. S. aureus strain Newman defective in IsdA and ClfB exhibited reduced but not comp letely defective adherence to sq uamous cells in indicating that other cell surface componen ts might also contribute. Results: Surface proteins IsdA, ClfB, and the serine-asp artic acid repeat proteins SdrC, SdrD and SdrE were investigated to determine their contribution to the adherence of S. aureus to desquamated nasal epithelial cells. This was achiev ed by expression of Cl fB, IsdA, SdrC, SdrD and SdrE on the surface of the surrogate Gram-positive host Lactococcus lactis and by isolating mutants of S. aureus Newman defective in one or more factor. The level of adherence of strains to squamous cells isolated from the nares of vol unteers was measured. Resu lts consistently showed that ClfB, IsdA, SdrC and SdrD ea ch contributed to the ability of S. aureus to adhere to squamous cells. A mutant lacking all four proteins was completely defective in adherence. Conclusion: The ability of S. aureus Newman to adhere to desquama ted nasal epithelial cells is multifactorial and involves SdrD an d SdrC as well as ClfB and IsdA