Shear Stress Affects the Kinetics of Staphylococcus aureus Adhesion to Collagen

Staphylococcus aureus is a major human pathogen that has been shown to bind collagen under static conditions. However, many staphylococcal infections are hematogenously acquired and adhesion events may be influenced by shear stress. In this study, we used a dynamic experimental system consisting of a parallel-plate perfusion chamber and phase-contrast video microscope to study the effects of shear stress on the adhesion kinetics of intact S. aureus to collagen surfaces in vitro. The adhesion of S. aureus Phillips to collagen types I, II, and IV was investigated over a physiologically relevant range of wall shear stresses at 37 °C. S. aureus PHIOO, a collagen adhesin-deficient mutant strain, was used as a control strain for the experiments. We found that S. aureus Phillips could adhere to collagens I, II, and IV at wall shear stresses less than 15 dyn/cm^2 and that the kinetics of the adhesion process were wall shear stress-dependent. Similar studies with PHIOO demonstrated that these cells are unable to adhere firmly to collagen surfaces. Transient interactions between PHIOO and the collagen surfaces were observed at low levels of shear stress suggesting that S. aureus may also interact with collagen by an alternative mechanism that does not lead to firm adhesion.