Antibacterial Activities of Five Medicinal Plants in Ethiopia against Some Human and Animal Pathogens

Objective To evaluate the in vitro antibacterial activities of five plant extracts which have been used as traditional medicines by local healers against three multidrug resistant bacteria, namely, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Results The highest mean zone of inhibition (4.66 mm) was recorded from methanol extract of Calpurnia aurea (Ait.) Benth. at a concentration of 200 mg/ml against S. aureus, followed by Croton macrostachyus Del. (4.43 mm) at the same dose and solvent for the same bacterial species, while methanol and chloroform extracts of E. brucei Schwein. did not inhibit growth of any bacterial species. The lowest value (100 μg/ml) of minimum inhibitory concentration (MIC) was observed from both methanol and chloroform extracts of C. aurea (Ait.) Benth. against all the three bacteria. The results of the positive control had no statistically significant difference (P > 0.05) when compared with crude extracts of C. aurea (Ait.) Benth. at concentration of 200 mg/ml against S. aureus. Conclusion The results of the present study support the traditional uses of these medicinal plants by the local healers. Except Erythrina brucei Schwein., all the plants investigated in this study exhibited antibacterial activities against the test bacterial species. Further researches are needed to be conducted to evaluate efficacy of these medicinal plant species on other microbes in different agroecological settings and their safety levels as well as their phytochemical compositions.