Synovial sepsis can be life-threatening in horses, and treatment of synovial sepsis can be complicated by the inability to culture offending microorganisms from synovial fluid. Multiple synovial fluid constituents, including proteins, hyaluronic acid, and other small molecules have been hypothesized to confer antimicrobial properties to synovial fluid; however, the role of mucins and mucin-like glycoproteins has not been investigated. The broad objectives of this proposal are to: identify bacterial isolation and antimicrobial sensitivity patterns in equine synovial fluid sepsis; determine if synovial fluid mucin depletion improves positive bacterial culture rates; and investigate the ability of recombinant mucins to inhibit bacterial growth and biofilm formation in equine synovial fluid. Our studies will provide both epidemiological and mechanistic insight into equine synovial fluid sepsis, with the potential to guide appropriate clinical antimicrobial therapy, minimize antibiotic resistance, and develop
techniques that could enhance our ability to isolate bacteria from septic synovial fluid structures.

To investigate these questions, a retrospective analysis of synovial fluid samples submitted to the Animal Health Diagnostic Center (AHDC) from horses with suspected synovial sepsis from both Cornell-affiliated hospitals and equine private practices will be performed to characterize microbial isolates and evaluate antimicrobial susceptibility data. Factors associated with the likelihood of positive synovial fluid culture will be evaluated, and 16S rRNA PCR will be performed to determine whether specific bacterial taxa correlate with positive or negative synovial fluid culture. Equine synovial fluid samples will be used to investigate the effect of synovial fluid mucin and lubricin depletion on the ability to culture model organisms, including Pseudomonas aeruginosa (P.aeruginosa), Staphylococcus aureus (S. aureus), and Escherichia coli (E. coli) in vitro. The ability of recombinant mucins, including the mucin-like glycoprotein lubricin, to inhibit bacterial proliferation and biofilm formation will be evaluated in bacterial culture media and synovial fluid.