Evaluation of the in Vitro Antimicrobial Efficacy of Solanum Indicum Extract Against Staphylococcus Aureus Isolates: A Potential Alternative to Conventional Antibiotics

Abstract

The increase of antimicrobial resistant pathogens within Zimbabwe's dairy industry has necessitated an urgent need for alternative treatments. This growing challenge directly threatens both animal health and farm productivity. Consequently, there is a critical and timely shift toward exploring plant-based solutions for mastitis management. These natural alternatives offer a promising avenue to improve dairy cow health while helping to preserve the efficacy of existing antimicrobial medicines for future use. This study evaluated the in vitro antimicrobial potential of Solanum indicum (Indian nightshade) leaf extract against Staphylococcus aureus, a primary causative agent of bovine mastitis. Milk samples from clinical routine testing were collected, and S. aureus was isolated and confirmed using selective media Mannitol Salt Agar, Gram staining, catalase, and coagulase tests. A methanol extract of S. indicum was prepared via cold maceration and tested at varying concentrations (1:0, 3:1, 1:1, 1:3 extract to solvent ratios) using the agar well diffusion method. Ampicillin and a methanol control served as positive and negative controls, respectively. The zones of inhibition obtained were 16.7mm for the highest concentration extract. The results demonstrated that the S. indicum extract exhibited intermediate antimicrobial activity against S. aureus isolates, with the highest concentration (1:0) showing a mean inhibition zone comparable to that of ampicillin. Statistical analysis revealed a significant difference (p < 0.05) between the extract's efficacy and the negative control. These findings suggest that S. indicum possesses potent bioactive compounds effective against S. aureus, supporting its potential as a sustainable, plant based alternative therapy for treatment of bovine mastitis infections in dairy cows.