Short CommunicationBacillus subtilis Strain PB6 Demonstrates Growth Inhibition Toward Equine-Specific Bacterial Pathogens

•Bacillus subtilis PB6 has previously demonstrated probiotic effects in livestock and poultry.•PB6 exhibited inhibitory activity against equine bacterial pathogens in vitro.•PB6 has potential for use as a probiotic in equine.

This study determined the antagonistic activity of a probiotic Bacillus subtilis strain PB6 (PB6) toward six bacterial pathogens of equine origin. Antimicrobial activity of PB6 was evaluated using two different in vitro methodologies. A streak line assay resulted in measurable zones of clearing between growth of PB6 and Clostridium difficile, Clostridium perfringens, Rhodococcus equi, and Streptococcus equi. A broth micro dilution assay using cell-free supernatant from PB6 culture demonstrated inhibition of Salmonella Typhimurium and R. equi growth. The results indicate the potential for PB6 to be a beneficial probiotic for use in the equine industry.