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Infectious arthritis is difficult to treat in both human and veterinary clinical practice. Recent literature reports Staphylococcus aureus as well as other gram-positive and gram-negative isolates forming free-floating biofilms in both human and equine synovial fluid that are tolerant to traditional antimicrobial therapy. Using an in vitro equine model, we investigated the ability of platelet-rich plasma (PRP) formulations to combat synovial fluid biofilm aggregates. Synovial fluid was infected, and biofilm aggregates allowed to form over a 2-hour period. PRP was collected and processed into different formulations by platelet concentration, leukocyte presence, and activation or lysis. Infected synovial fluid was treated with different PRP formulations with or without aminoglycoside cotreatment. Bacterial load (colony-forming unit/mL) was determined by serial dilutions and plate counting at 8 hours posttreatment. All PRP formulations displayed antimicrobial properties; however, formulations containing higher concentrations of platelets without leukocytes had increased antimicrobial activity. Lysis of PRP and pooling of the PRP lysate (PRP-L) from multiple horses as compared to individual horses further increased antimicrobial activity. This activity was lost with the removal of the plasma component or inhibition of the proteolytic activity within the plasma. Fractionation of pooled PRP-L identified the bioactive components to be cationic and low-molecular weight (<10 kDa). Overall, PRP-L exhibited synergism with amikacin against aminoglycoside tolerant biofilm aggregates with greater activity against gram-positive bacteria. In conclusion, the use of PRP-L has the potential to augment current antimicrobial treatment regimens which could lead to a decrease in morbidity and mortality associated with infectious arthritis.
Gilbertie et al. (Fri,) studied this question.