The main purpose of this study was to analyze the major groups of secondary compounds of Calpurnia aurea and evaluate the antibacterial activity of their crude extracts against specific bacterial strains as (Escherichia coli O157:H7, and Staphylococcus aureus). Fresh leaves and bark of Calpurnia aurea were randomly collected from the Hosanna district in southern Ethiopia. Extraction of the sample was done by using ethanol and phytochemical analysis was carried out using a standard protocol and the contents of extracts were determined using spectrophotometric. The antibacterial effectiveness of extracts was examined against Escherichia coli O157:H7 and Staphylococcus aureus using the disc diffusion method. The antibacterial activity of ethanol extract from leaves and bark revealed of inhibition against Escherichia coli O157: H7 and Staphylococcus aureus. The average suppression zone in the diameter range was between 11.8 and 17.4 millimeters ethanolic leaf extract of Calpurnia aurea showed significant inhibition zones in Escherichia coli O157: H7 and Staphylococcus aureus. Dimethyl sulfoxide used as a negative control showed no activity. This study depicts the presence of phenolic compounds, saponins, flavonoids, alkaloids, and other phytochemicals associated with Calpurnia aurea leaves and bark. Ethanol extract showed antibacterial activity against Escherichia coli O157: H7 and Staphylococcus aureus. Therefore, the results of the current study suggest that the ethanol extract of Calpurnia aurea has an antibacterial activity on the test pathogens for the pathogen used in the current study. Further research on total microorganisms is needed.











