During the 2020 American Association of Equine Practitioners’ Convention, held virtually, North Carolina State University veterinary researcher Lauren Schnabel, DVM, PhD, Dipl. ACVS, ACVSMR, highlighted her team’s encouraging results using a novel therapy called platelet-rich plasma lysate (PRP-L) to treat joint infections caused by the common bacterium Staphylococcus aureus.
“PRP-L shows great promise as a therapy against antimicrobial-tolerant infections in synovial (joint) fluid biofilms,” said Schnabel. “It has the potential to decrease both morbidity (illness) and mortality associated with equine joint infections.”
PRP-L is produced by collecting platelets from healthy donor horses’ blood plasma. Those platelets are then highly concentrated, up to 50 times, and broken apart (lysed) to release all their potent antimicrobial peptides (proteins that attack bacteria) and other healing cytokines (inflammatory mediators).
The peptides and mediators in the PRP-L help eradicate biofilms created by S. aureus–free-floating aggregates that basically protect the bacteria against any antimicrobials a veterinarian might administer to treat the joint infection. PRP-L itself can dramatically reduce biofilm burden, said Schnabel: When administered in conjunction with an antimicrobial such as amikacin (used to treat bacterial infections), PRP-L can, in theory, rapidly clear the infection and prevent OA development.
Schnabel and her team tested the validity of this treatment approach in by inoculating each of 12 live horses in a single hock (tarsocrural) joint with S. aureus. They treated the horses with either intra-articular amikacin or a combination of amikacin and PRP-L for seven days. All horses also received a systemic antibiotic and anti-inflammatory for 10 days.
Key findings were:
- Horses treated with PRP-L and amikacin had lower pain scores and joint effusion (swelling) than control horses treated with amikacin alone;
- PRP-L- and amikacin-treated horses had lower synovial fluid and synovial tissue bacterial counts, as well as lower inflammatory parameters noted in synovial fluid and plasma samples collected during the study period; and
- Ultrasonographic and microscopic analysis of joint tissues confirmed lower levels of inflammation and less joint damage in PRP-L-treated horses.
“In sum, bacteria such as S. aureus that form biofilms in joints are recalcitrant to standard antimicrobial drugs,” said Schnabel. “Using PRP-L, preferably that pooled from multiple horses, combats the bacteria in these biofilms and restores the efficacy of antimicrobials.”