In vitro antibacterial activity of selected medicinal plant extracts against Escherichia coli in Adami Tulu Jiddo Kombolcha district, Ethiopia

Abstract Background The increasing prevalence of antimicrobial-resistant Escherichia coli necessitates the exploration of alternative antimicrobial agents from botanical sources. Objective: This study evaluated the in vitro antibacterial activity of methanolic and ethanolic leaf extracts of Datura stramonium , Balanites aegyptiaca , and Acokanthera schimperi against field and reference strains of E. coli . Methods: Following phytochemical screening, antibacterial activity was determined using the disk diffusion method, while Minimum Inhibitory Concentrations (MIC) and Minimum Bactericidal Concentrations (MBC) were determined using the broth dilution method. Results: All extracts demonstrated concentration-dependent inhibitory effects. The methanolic extract of D. stramonium (100 mg/mL) exhibited the highest antibacterial activity, producing a zone of inhibition of 20.27 ± 0.37 mm against the field isolate. This inhibition zone was similar to that of the ciprofloxacin positive control (19.7 ± 0.3 mm). Methanol consistently demonstrated higher extraction yield and antibacterial activity than ethanol across most tested species. D. stramonium and A. schimperi showed MIC values as low as 0.78 mg/mL, while all extracts exhibited bactericidal activity based on an MBC/MIC ratio of 2. Conclusion: These findings support the potential of the selected medicinal plants as sources of antibacterial compounds and provide a basis for further investigations involving bioactive compound characterization, safety assessment, and in vivo validation.