<i>In-vitro</i> assessment of the efficacy of herb-herb combinations against multidrug-resistant mastitis-causing bacteria: <i>Staphylococcus aureus</i> and <i>Klebsiella pneumoniae</i>

The threat of antibiotic resistance and the antecedent evolution of harmless microbes into superbugs is an epidemic of global concern. This study assessed the in-vitro herb to herb antibacterial activity of acetone, methanol, and water extracts of Ximenia caffra Sond. Myrothamnus flabellifolius Welw. Allium sativum L, and Cinnamomum verum J.Presl. against multidrug-resistant (MDR) mastitogenic Staphylococcus aureus and Klebsiella pneumoniae. Their minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC), and zone of inhibition against S. aureus and K. pneumoniae were measured using a microplate serial dilution technique and agar-well diffusion method. All the acetone and methanol plant extracts showed antimicrobial activity against MDR isolates tested. The MIC for acetone and methanol extracts against S. aureus and K. pneumoniae ranged from 6–25 mg/mL and decreased in the combined herbs from 1 mg/mL to 13 mg/mL. The MBC for acetone and methanol extracts against the tested bacteria ranged from 6–50 mg/mL. The acetone and methanol extracts had inhibition zones against S. aureus and K. pneumoniae ranging from 14–22 mm. The plant extracts showed a synergistic effect when combined with Gentamycin and Lincomycin as the zone of inhibitions was increased and ranged from 25–29 mm. Findings indicate that all the extracts had a dose-dependent inhibitory effect on the growth of multidrug-resistant S. aureus and K. pneumoniae. The study’s findings further reinforce the importance of these extracts in traditional veterinary and healthcare practices. As a result, this study concludes that antibiotics and plant extracts can be administered concurrently to treat mastitis caused mostly by S. aureus and K. pneumoniae.