Background: Therapeutic potential of equine platelet lysate (ePL) for treatment of respiratory disease in horses remains unknown. Hypotheses/
Objectives: To characterize and compare pre- and post-nebulized ePL according to protein composition and in vitro antimicrobial activity against clinically relevant respiratory pathogens. Differences between pre- and post-nebulized ePL were not expected. Animals: Pooled ePL from 3 healthy horses.
Methods: Sterile ePL nebulized condensate was collected via mesh nebulizer. Flow rate and aerosolized particle size distribution were quantified. Pre- and post-nebulized ePL aliquots were compared according to: growth factor, antimicrobial peptide and cytokine concentrations; proteomic analysis; and bacterial growth inhibition parameters [maximum growth (µ); carrying capacity (K)] for Streptococcusequi subsp zooepidemicus and Rhodococcus equi (susceptible and MDR) clinical isolates using pre- and post-nebulized ePL concentrations of 50% (PreN50, PostN50).
Results: Flow rate and median particle size were 0.8 ml/min and 4.991 µm with 52% of particles ≤5 µm. Differences in cytokine, growth factor, or proteomic analysis were not identified between pre- and post-nebulization (P > 0.1). Negative effects on K were noted for S. zooepidemicus (PreN50, p= 0.009; PostN50, p= 0.009)) and E. coli (PreN50, p= 0.05) compared to BHI. No effect on condition was observed on µ for S. zooepidemicus and E. coli. For R. equi-MDR and R. equi (WT), K and µ were positively affected by all PL treatments (PreN50 and PostN50, p≤ 0.05). Conclusions and clinical importance: Bacterial growth inhibition of ePL is organism dependent but nebulization does not appear to affect protein composition. Further research is recommended to better characterize ePL antimicrobial activity against clinically relevant pathogens and suitability for nebulization in horses.