Antibiotic Properties of Ethanol Extract of Chromolaena odorata (Asteriaceae)

Ethanol extract of Chromolaena odorata was assayed for in vitro antibiotic activity using agar diffusion and plate dilution methods. The extract produced measurable zones of inhibition (6.5–16 mm) against reference microbial strains and hospital isolates including Bacillus thuringiensis (var israeli), Bacillus stearothermophilus (NCTC 10339), Staphylococcus aureus (NCTC 6571), Escherichia coli (NCTC 11699), Pseudomonas sp., Streptococcus faecalis and Klebsiella sp. Ampicillin, gentamycin and tetracycline, which were used as antibiotic controls gave inhibition zones measuring between 3.0 and 24 mm while the zones obtained in assays with phenol measured 0.5–1.0 mm. The minimum inhibitory concentration of the extract was 0.13–8.0 mg/ml. The antibiotic activity was lost or significantly reduced with increasing pH in the alkaline spectrum. Zones of inhibition were also diminished by heating the extract (40–80°C) although its antimicrobial activity was not totally lost when heated to 120°C. The antibiotic substance produced a cidal effect on the bacteria. It also resulted in the lysis and variable gram reactions in some of the cells observed, suggesting that the site of action might be the cell wall of the susceptible bacteria.