<i>Staphylococcus epidermidis</i> Affinity for Fibrinogen-Coated Surfaces Correlates with the Abundance of the SdrG Adhesin on the Cell Surface

<i>Staphylococcus epidermidis</i> is a world-leading pathogen in healthcare facilities, mainly causing medical device-associated infections. These nosocomial diseases often result in complications such as bacteremia, fibrosis, or peritonitis. The virulence of <i>S. epidermidis</i> relies on its ability to colonize surfaces and develop thereupon in the form of biofilms. Bacterial adherence on biomaterials, usually covered with plasma proteins after implantation, is a critical step leading to biofilm infections. The cell surface protein SdrG mediates adhesion of <i>S. epidermidis</i> to fibrinogen (Fg) through a specific “dock, lock, and latch” mechanism, which results in greatly stabilized protein–ligand complexes. Here, we combine single-molecule, single-cell, and whole population assays to investigate the extent to which the surface density of SdrG determines the ability of <i>S. epidermidis</i> clinical strains HB, ATCC 35984, and ATCC 12228 to bind to Fg-coated surfaces. Strains that showed enhanced adhesion on Fg-coated polydimethylsiloxane (PDMS) were characterized by increased amounts of SdrG proteins on the cell surface, as observed by single-molecule analysis. Consistent with previous reports showing increased expression of SdrG following <i>in vivo</i> exposure, this work provides direct evidence that abundance of SdrG on the cell surface of <i>S. epidermidis</i> strains dramatically improves their ability to bind to Fg-coated implanted medical devices