Studies on in vitro interaction of ampicillin and fresh garlic extract against Staphylococcus aureus by checkerboard method

OBJECTIVE: Staphylococcus aureus has largely developed resistance to the multiple antimicrobial agents. Garlic (Allium sativum) is claimed to retard development of resistance and produce synergy with conventional antimicrobial agents. The aim of the present study was to evaluate the effect of combination of ampicillin with fresh garlic extract (FGE) against S. aureus by using in vitro method. MATERIALS AND METHODS: Antimicrobial activity of FGE was studied by well diffusion and broth dilution methods. The effect of combination of ampicillin with FGE was studied by using checkerboard method against the clinical isolates of S. aureus. The organisms were exposed to individual antimicrobial as well the different combinations of the two agents and minimum inhibitory concentration was measured. RESULTS: Synergistic interaction was observed by the combination of FGE with ampicillin for all the strains of S. aureus. Mean minimum inhibitor concentration (MIC) of ampicillin per se was 24 μg/ml. Addition of 30-60 mg/ml of FGE reduced MIC of ampicillin to <2 μg/ml. CONCLUSION: This in vitro study indicates synergism between FGE and ampicillin against S. aureus. Evaluation of these combinations in vivo may be warranted.