Phytochemical Screening and Determination of Antibacterial Activity of Garlic Extracts against Clinical Isolates of Staphylococcus aureus

The growing threat of drug resistant bacteria, particularly Staphylococus aureus, has become a pressing concern for global public health. Garlic (Allium sativum L.) widely used for culinary and medicinal purposes, is known for its broad spectrum antimicrobial activity, primarily due to the presence of allicin as its key bioactive compound. This study aimed to evaluate the phytochemical constituents and antibacterial activity of garlic extract against clinical isolates of S. aureus. Clinical isolates of S.aureus were obtained from Aminu Kano Teaching Hospital Kano, screened and confirmed using microbiological standard methods. Fresh garlic bulbs were processed and extracted using aqueous, methanol and ethanol solvents. Phytochemical screening of the extracts was carried out using standard qualitative methods to detect bioactive compounds. The antibacterial activity was assessed against clinical isolates of S. aureus using the agar disc diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth dilution techniques. Phytochemical analysis revealed the presence of alkaloids, flavonoids, saponins, tannins, steroids, phenolics and terpenoids in both extracts, with higher intensity observed in the ethanol extract. The garlic extracts exhibited significant antibacterial activity against test S. aureus, producing concentration-dependent zones of inhibition. The ethanol extract demonstrated greater (25±1.5 mm) antibacterial efficacy compared to the aqueous extract (20±1.5 mm), with lower MIC and MBC values 6.25 mg/ml. Ciprofloxacin was used as control antibiotic and had a zone of inhibition between 17 mm-25 mm. There was no significant difference between diameter zones of inhibition of methanol, ethanol and aqueous extracts at P = 0.50 and P = 0.97against the isolates. Garlic extract possesses potent antibacterial activity against clinical isolates of S. aureus, which could be attributed to its diverse phytochemical constituents. These findings support the potential use of garlic as a natural antimicrobial agent and provide a scientific basis for its traditional use in the management of S. aureus infections.