Abstract 356: Adhesion of Staphylococcus Epidermidis to Fibrinogen Alters Clot Formation Kinetics and Ultimate Stiffness

Abstract

Bacterial infection is known to increase the risk for thromboembolism. The mechanism underlying this correlation remains largely unknown. We recently showed that the common pathogen Staphylococcus epidermidis retards clot formation, increases clot elasticity and generates a heterogeneous clot structure that remodels over time. Here, we elucidate the mechanism of this process by evaluating the capacity for S. epidermidis to bind to fibrinogen as a function of its growth phase. We hypothesized that the effect of S. epidermidis on a fibrin clot is related to its propensity toward biofilm formation. Therefore, stationary phase (biofilm-like) S. epidermidis will have a more robust effect on clot kinetics and elasticity than exponential phase (planktonic). Furthermore, this difference is mediated by increased adhesion to fibrinogen. Rheometry was used to evaluate the formation and resultant elasticity of fibrin clots with exponential or stationary phase S. epidermidis . A functional in vitro model was developed to evaluate adhesion of S. epidermidis to a fibrinogen coated surface in a continuously flowing environment. Fluorescent labeled exponential and stationary phase S. epidermidis were visualized flowing through a parallel plate microfluidic chamber past immobilized fibrinogen. Images were obtained every 3 seconds for 30 min. Bacterial deposition rate and mean adhesion time were quantified by automated image analysis. A paired Student’s t-test was used for statistical analysis. Stationary phase S. epidermidis retards clot formation and increases resultant elasticity while exponential phase only slightly reduces elasticity. The bacterial deposition rate onto fibrinogen was significantly (p=0.03) greater for stationary phase (1741 ± 1513 cells/cm 2 · sec -1 ) vs exponential phase (676 ± 270 cells/cm 2 · sec -1 ). The average adhesion time however was similar for exponential and stationary phase cells. Coagulation proteins can provide a framework for bacterial adhesion, biofilm formation and infection. In turn infected thrombi with (biofilm-like) bacteria are stiffer which correlates to more frequent bacterial binding to fibrinogen. This provides a potential molecular mechanism for infection mediated thromboembolic events.