Antibacterial activity of Tribulus terrestris methanol extract against clinical isolates of Escherichia coli

Abstract

Summary Introduction: Tribulus terrestris L. is traditionally used for treatment of urinary tract infections. Escherichia coli, as the most prominent agent of urinary tract infections, can be sensitive to T. terrestris extract. Objectives: The aim of this study was to evaluate the antibacterial activity of T. terrestris methanol extract against clinical isolates of E. coli from urinary tract infections. Saponins were determined as main constituents of T. terrestris methanol extract. Methods: The antibacterial activities of T. terrestris methanol extract were evaluated by micro-broth dilution assay. The synergistic effects of T. terrestris methanol extract were screened with gentamicin by micro titer plate and disc diffusion assays. The isobologram curve was figured and the Fractional Inhibitory Concentration Index (FICI) was determined. Results: The saponin content of T. terrestris methanol extract was 54% (w/w). The means of MIC and MBC values for E. coli clinical isolates (n=51) were 3.5±0.27 and 7.4±0.5 mg/ml while these amounts were 3.9±1.3 and 6.4±1.8 μg/ml for gentamicin. T. terrestris methanol extract and gentamicin had synergistic effect with FICI equal to 0.1375. Conclusion: Therefore, T. terrestris can be applicable as alternative treatment in management of urinary tract infections.