A new approach to infectious arthritis: understanding bacterial behavior in synovial fluid and developing a novel therapeutic that is both antimicrobial and chondroprotective

 

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Author: Lauren Schnabel
 
Infectious arthritis can lead to persistent infection necessitating euthanasia or to degenerative joint disease in patients that survive. Our group has previously shown that bacteria grown in equine synovial fluid (SynF) form free-floating biofilms termed biofloats that are recalcitrant to antimicrobial therapy. We have also shown that platelet-rich plasma lysate (PRP-L) possesses potent bactericidal effects against S. aureus biofloats in vitro. Based on these findings, we used a model of equine S. aureus induced infectious arthritis to test the ability of PRP-L to combat biofloats in vivo. Horses (n=12) were inoculated with S. aureus in one tarsocrural joint and treated with intra-articular amikacin alone (control, n=6) or in combination with PRP-L (treatment, n=6) starting 24hr post-infection and continued daily for 7 days. All horses received systemic antimicrobials until day 10 and tapering phenylbutazone throughout the study. SynF and blood were evaluated at days 0-7, 14 and 21. Pain scoring and ultrasound examinations were also performed at these time points. At day 24 post-infection, horses were euthanized and synovium and cartilage was collected. Horses treated with PRP-L had lower pain scores (p<0.003), lower levels of systemic inflammatory proteins (p<0.0003), and decreased SynF parameters of infection (p<0.02) and inflammation (p<0.05) compared to control horses. PRP-L treated horses also had significantly lower bacterial loads in SynF (p<0.006) and end-term synovium (p<0.01) compared to control horses. While results such as ultrasonographic and histological scoring are still pending, results to date strongly support the use of PRP-L in combination with antimicrobials to treat infectious arthritis.[/um_loggedin]