Ashok Boora, Sarita Yadav, Sunita Yadav, Nishu and Rajesh Kumar Lohchab
Abstract
Mastitis remains one of the most economically important diseases in dairy animals, with antibiotic resistance posing a major challenge to effective treatment. This study investigated the synergistic antibacterial activity of methanolic propolis extract (MPE) in combination with gentamicin against major mastitis-causing pathogens in buffaloes. Staphylococcus aureus, Escherichia coli, and Pseudomonas spp. were isolated from mastitic milk samples and identified using conventional and automated methods. The minimum inhibitory concentration (MIC) of MPE was determined to be 7.81 mg/mL, while gentamicin exhibited an MIC of 31.25 mg/ml. Synergistic interactions were evaluated using the checkerboard microdilution assay, and the fractional inhibitory concentration index (FICI) confirmed synergy (lowest FICI = 0.313). The combination of MPE and gentamicin resulted in a 16-fold reduction in the required concentration of propolis and a 4- fold reduction in gentamicin compared to their individual MICs. These findings highlight the potential of propolis to enhance the efficacy of conventional antibiotics, offering a promising alternative strategy for reducing antibiotic usage and combating resistance in the management of buffalo mastitis. Further in vivo studies are warranted to validate these results.