The Influence of Human Serum on Staphylococcus aureus Growth, Collagen and Fibrinogen Receptor Expression and Adhesion to Immobilized Collagen and Fibrinogen under Dynamic Shear Conditions

Staphylococcus aureus is a major pathogen, known to cause a wide variety of infections, such as endocarditis, pneumonia, osteomyelitis, and septic arthritis. The binding of S. aureus to extracellular matrix and serum proteins is considered the first and most critical step in the infection process. Previous studies have evaluated the adhesion of S. aureus to various proteins; some of these experiments have been done with and without the influence of fluid shear in buffer, buffer supplemented with plasma proteins or in whole plasma. In particular, S. aureus adhesion to collagen and fibrinogen has been extensively studied in this laboratory under hydrodynamic conditions. These and similar studies have yet to investigate the effect of serum on S. aureus growth, adhesin expression or subsequent adhesion. This study for the first time describes the adhesion profile of S. aureus grown in human serum to collagen and fibrinogen under physiologically relevant fluid shear conditions. These studies have shown that S. aureus grown in the presence of serum have reduced bacterial growth, specific growth rate, receptor expression and the effective adhesion rate to collagen and fibrinogen. The data suggest that there is a biological factor in human serum inhibiting bacterial growth, CNA and ClfA receptor expression, and adhesion rate. The elucidation of what this factor is in the future, will provide a better understanding of the pathogenesis of S. aureus, and possibly lead to better therapeutic strategies