Platelet‐rich plasma lysate displays antibiofilm properties and restores antimicrobial activity against synovial fluid biofilms in vitro

Abstract

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.

Toll‐like receptor activation of equine mesenchymal stromal cells to enhance antibacterial activity and immunomodulatory cytokine secretion

“…Evolving treatments to improve outcomes in chronically infected nonhealing tissues include implant surface coatings, local antibiotic release systems, and biological therapies. [25][26][27][28][29][30][31] Mesenchymal stromal cells (MSCs) possess antimicrobial and immunomodulatory properties and are particularly attractive as adjunctive therapies to antibiotics as they are not subject to development of antimicrobial resistance. 29,[31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] MSCs are vital participants in normal tissue repair processes, promoting healing through angiogenesis, epithelialization, collagen deposition, granulation tissue formation, and release of inflammatory mediators.…”

Susceptibility of canine chondrocytes and synoviocytes to antibiotic cytotoxicity in vitro

“…However, it is recognized that doses several-fold greater than MIC may be required to kill bacteria in synovial biofilms present in septic arthritis, as has been previously reported in vitro. 35 These findings provide sufficient evidence to recommend that doses for in vivo IA antibiotic administration in dogs should be further assessed for safety and efficacy at concentrations greater than MIC and at or below determined IC50 for each antibiotic.…”

“…[38][39][40] Finally, bacterial biofilms in septic arthritis, either attached to the synovial lining or free-floating in synovial fluid, may limit efficacy of IA-administered antibiotics, requiring higher doses to be used to be effective. 35 In some cases, it may not be possible to achieve bactericidal doses that are not simultaneously cytotoxic when treating biofilms, which warrants further evaluation in vivo.…”

“…Increased synovial effusion and vascularization associated with synovial inflammation in septic arthritis may affect antibiotic concentrations and activity in vivo; amikacin administered IA in horses with inflamed joints reached lower concentrations than that administered in normal joints, 9 resulting in altered distribution of pharmaceuticals 38‐40 . Finally, bacterial biofilms in septic arthritis, either attached to the synovial lining or free‐floating in synovial fluid, may limit efficacy of IA‐administered antibiotics, requiring higher doses to be used to be effective 35 . In some cases, it may not be possible to achieve bactericidal doses that are not simultaneously cytotoxic when treating biofilms, which warrants further evaluation in vivo.…”

Use of in vitro assays to identify antibiotics that are cytotoxic to normal equine chondrocytes and synovial cells

“…Finally, it is conceivable that the presence of sepsis, or inflammatory mediators associated with sepsis, may alter antibiotic cytotoxicity profiles as well as drug distribution from the joint due to increased inflammation, but this was beyond the scope of the current study. The ability of bacterial pathogens to form biofilms in septic arthritis, either attached to each other free‐floating in synovial fluid or along the synovial lining, may limit efficacy of IA antibiotics, requiring higher doses 39 . The initial in vitro studies reported here were necessary to determine IC50 levels in normal joint cells and compare cytotoxicity between antibiotics to move forward with additional work that would account for other variables encountered clinically.…”