In vitro antimicrobial activity of three medicinal plants of Ethiopia against some selected bacterial isolates

Medicinal plants constitute natural source of antimicrobial drugs that will provide essential compounds to fight against disease. In this study, the antibacterial activity of ethanol extracts of Moringa stenopetala, Thymus serrulatus, and Terminalia brownii were investigated against selected pathogenic Gram positive and Gram negative bacteria. In vitro antibacterial activities of the ethanol extracts were tested at a concentration of 50, 25, and 12.5 mg/ml by using agar disc diffusion method and zone of inhibitions were determined. Furthermore, minimum inhibitory concentrations were determined for plants that showed antibacterial activity (>15 mm zone of inhibition). The results indicated that only T. serrulatus and T. brownii exhibited antimicrobial activity against one or more test pathogens. Both extracts of these plants showed strong and dose dependent activity when compared with M. stenopetala which demonstrated no activity. Interestingly, T. serrulatus showed broad spectrum activity against the tested bacteria. Therefore, ethanol extracts of T. serrulatus and T. brownii showed promising antimicrobial activity justifying their usage in traditional medicine.