In vitro antibacterial and growth-inhibitory effects of a pure Salvia officinalis powder extract against selected veterinary bacterial pathogens

This study investigated the in vitro antibacterial and growth-inhibitory effects of a commercially available powdered Salvia officinalis extract against clinically important bacteria isolated from bovine mastitis, poultry litter, and urogenital and respiratory infections in cats and dogs. Escherichia coli, Salmonella spp., methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella spp., Pseudomonas aeruginosa, and Proteus spp. were evaluated using disk diffusion and growth inhibition tests on extract-supplemented media. Disk diffusion assays showed measurable antibacterial activity against all tested bacteria, with inhibition zone diameters decreasing as extract concentration decreased, indicating a concentration-dependent response. The largest inhibition zones were observed at the highest concentration (1/1), particularly for P. aeruginosa (29 mm), Salmonella spp. (27 mm), and MRSA (26 mm), while Klebsiella spp. and E. coli exhibited comparatively lower susceptibility. On Mueller–Hinton agar supplemented with the extract, reduced visible growth was observed for E. coli, Klebsiella spp., and Proteus spp. at the 1/8 concentration, and complete inhibition occurred at 1/4. In Salmonella spp., growth decreased further with increasing extract concentration. Visible growth of MRSA and P. aeruginosa was no growth at both concentrations in agar plates. Overall, the antibacterial response was species-dependent and generally concentration-related. As biological replicates were not included, findings were presented descriptively and considered preliminary. The results indicate that powdered S. officinalis extract exhibits measurable inhibitory activity against veterinary pathogens, with the most pronounced effects against MRSA and P. aeruginosa. Further replicated studies and in vivo safety, efficacy, and dosage evaluations are required before practical application.