Determining the impact of host-synovial fluid factors on Staphylococcus aureus aggregation

Abstract Chronic periprosthetic joint infections (PJIs) are serious complications of joint replacement surgeries. These often require subsequent corrective surgeries, as well as many rounds of antibiotics, to correct. Over the past few years, staphylococci have been identified as one of the most common organisms to cause PJIs. Capable of forming biofilms, bacterial communities encased in an extracellular polymeric slime matrix, staphylococci infections can easily become very difficult to clear. This can be due to increased antimicrobial resistance conferred by the biofilm as well as the generation of persister cells. Current hypotheses suggest, prior to the formation of biofilms within PJIs, Staphylococcus aureus will form cellular aggregates. To investigate the development of S. aureus aggregates we will utilize fluorescence-activated cell sorting (FACS) and light microscopy to differentiate and analyze aggregated and non-aggregated populations. Formation of aggregates has been reported in the presence of numerous factors present in the fluid present in joints, known as synovial fluid. These factors include fibrin, fibronectin, and hyaluronic acid. Our preliminary data has shown that extracellular DNA (eDNA) might play a role in aggregation and it has been observed that eDNA is essential in the formation of biofilms. We sought to determine the contribution of these factors in the formation of S. aureus aggregates. Finally, while there are a number of formulations for artificial synovial fluid (ASF) based on matching viscoelastic parameters for in vitro wear testing, there is not a model designed with microbiological testing in mind. Herein, we developed an ASF based on the previously reported concentrations of proteins, lipids, extracellular DNA, as well as hyaluronic acid.