The need for cheap drug and the necessity to combat drug resistance have led to Ageratum conyzoides L being investigated against Bacillus subtilis, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans, C. stellatoidea and C. (torulopsis) glabrata using well diffusion methods and minimum inhibitory concentrations. The sensitivity of the bacteria and yeasts to the essential oil from the stem, leaves and root were determined. Pseudomonas aeruginosa was not sensitive to the essential oil. The minimum inhibitory concentrations ranged between 2.0 mg/ml and 4.0mg/ml and these were recorded for Bacillus subtilis, Klebsiella pneumoniae, and Staphylococcus aureus in the stem, leaves and the root extracts. All the microbes tested were sensitive to the essential oils of Ageratum conyzoides except Pseudomonas aeruginosa The observable inhibition of selected bacteria by oils of Ageratum conyzoides makes it a promising alternative antimicrobial agent.
