In-Vitro antibacterial activity of Garlic and Eucalyptus extracts against methicillin resistant Staphylococcus aureus and Escherichia coli

Abstract

The rise of antimicrobial resistance has increased interest in plant-based antibacterial agents as potential alternatives to conventional antibiotics. This study investigated the in-vitro antibacterial activity of ethanolic extracts of Allium sativum (garlic) and Eucalyptus globulus (eucalyptus) against Methicillin-Resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli). The research aimed to determine the phytochemical constituents of the extracts, evaluate their antibacterial effects using agar well-diffusion, and establish their Minimum Inhibitory Concentrations (MICs). Garlic bulbs and eucalyptus leaves collected from Buikwe District were authenticated, processed, and extracted using 70% ethanol. Phytochemical screening revealed that garlic contained flavonoids, saponins, tannins, phenols, and allicin, while eucalyptus contained alkaloids, flavonoids, tannins, phenols, and steroids. These compounds are known to exert antimicrobial effects through mechanisms such as membrane disruption and inhibition of essential metabolic processes. Antibacterial testing showed that both extracts inhibited the growth of MRSA and E. coli. Garlic produced inhibition zones of 14 mm (MRSA) and 16 mm (E. coli), whereas eucalyptus produced 18 mm and 20 mm, respectively. Ciprofloxacin, the positive control, produced the highest inhibition, confirming bacterial susceptibility, while DMSO showed no effect. MIC results demonstrated that garlic exhibited stronger antibacterial potency, with MIC values of 20 µg/mL for MRSA and 15 µg/mL for E. coli, compared to eucalyptus with 25 µg/mL and 30 µg/mL. These findings confirm that both A. sativum and E. globulus possess significant antibacterial activity, supporting their traditional use in treating bacterial infections. The study concludes that these medicinal plants offer promising, low-cost alternatives or supplementary agents in the management of infections, especially in regions affected by rising antibiotic resistance. Further research is recommended to investigate their mechanisms of action, safety profiles, and potential clinical applications.