"Four pathogens (Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella typhi) were used for the study of antimicrobial effects of Chromolaena odorata and Citrus aurantifolia leaf extracts. Solvents used for the extraction of the active ingredients of the plant leaves were water and ethanol. The antibiotics evaluated included erythromycin, tetracycline and penicillin. The antimicrobial effects of the plant extracts showed both extracts were inhibitory to the four pathogens. The minimum inhibitory concentration (MIC) of the extracts on the organisms ranged between 0.01563-0.0625mg mLG for Bacillus cereus, 0.0156-10.25 mg mLG for Staphylococcus aureus, 0.125-0.5 mg mLG for Escherichia coli and 0.25-0.5 mg mLG for 1 1 1 Salmonella typhi. The effects varied with solvent type of extract, concentrations of the leaf extract and the organisms. Erythromycin was inhibitory to Bacillus cereus, Staphylococcus aureus and Salmonella typhi, tetracycline was inhibitory to Bacillus cereus and Staphylococcus aureus while penicillin was inhibitory only to Staphylococcus aureus. The three antibiotics had no cidal or static effect on Escherichia coli. The antimicrobial effect of leaf extracts of Chromolaena odorata and Citrus aurantifolia is discussed in relation
to the development of drugs or antimicrobial agents in Nigeria."