Fluid shear influences binding magnitude of S. aureus suspended in blood to collagen

S. aureus is responsible for many blood-born infections and has demonstrated increasing antibiotic resistance. S. aureus-collagen binding interactions have been shown important in infections such as osteomyelitis and septic arthritis. However, their role in blood-born infections has not been determined. In infective endocarditis, bacteria and platelets combine forming thrombi on the traumatized vasculature surface. In this process collagen serves as a potential binding surface for S. aureus. Platelets and S. aureus both bind collagen under shear conditions, with platelets being much more reactive. We examined the ability of S. aureus cells suspended in whole blood to bind a collagen surface under physiologically low (100 s^-1) and high (1000 s^-1) fluid shear conditions. A parallel plate flow chamber was used to create a defined shear environment. The location (at the collagen surface or in the platelet aggregate above the collagen surface) and number of bacteria cells were quantified under fluorescence using confocal laser microscopy. Despite the highly reactive platelet/collagen interactions, results demonstrate that under both shear conditions the S. aureus cells bind the collagen surface in significant number. However, there are more S. aureus-collagen interactions under low shear conditions than high, where the S. aureus-platelet interactions are more abundant.