Bacteriostatic effect of equine pure platelet-rich plasma and other blood products against methicillin-sensitive Staphylococcus aureus. An in vitro study.

OBJECTIVES: 1) To evaluate the bacteriostatic in vitro effect of pure platelet-rich plasma (P-PRP), pure platelet-rich gel (P-PRG), leukocyte-poor gel (LPG), platelet-poor plasma (PPP), and heat inactivated plasma (IP) against methicillin-sensitive Staphylococcus aureus (MSSA) over a period of 24 hours. 2) To determine the degradation of platelet factor-4 (PF-4), transforming growth factor beta 1 (TGF-β1), and platelet-derived growth factor isoform BB (PDGF-BB) in these equine blood components. 3) To establish correlations between platelet and leukocyte counts, PF-4 concentrations, and MSSA growth.

METHODS: Fourteen horses were used. Blood components were obtained by a manual protocol. Every blood component was mixed with MSSA and Müller-Hinton Broth and cultured at 37°C for 24 hours. Samples for the determination of bacterial growth (colony-forming units) and PF-4, TGF-β1 and PDGF-BB concentrations were taken at one, four, eight, 12 and 24 hours.

RESULTS: The bacterial growth was significantly (p = 0.01) inhibited for P-PRP, P-PRG, LPG and PPP in comparison with IP and, the positive control group during the first 12 hours. The P-PRG had higher and sustained TGF-β1 and PDGF-BB concentrations over time in comparison with the other blood components.

CLINICAL SIGNIFICANCE: The plasma complement could be one of the most responsible components of the in vitro bacteriostatic effect of P-PRP, P-PRG, LPG and PPP against MSSA. Additionally, P-PRG was the better biomaterial because it had an acceptable bacteriostatic effect and the highest concentration of growth factors.