Antibacterial Activity of Essential Oil of Corymbia citriodora Leaves against Escherichia coli and Staphylococcus aureus

Aim: To examine the antibacterial activity of essential oil of Corymbia citriodora leaves on two clinically significant microorganisms, Escherichia coli and Staphylococcus aureus.

Place and Duration of the Study: The experiment was conducted in Science Laboratory at Malawi College of Forestry and Wildlife, Dedza, Malawi between July and September 2013.

Methodology: The essential oil of C. citriodora leaves were obtained by hydrodistillation method. The inhibitory effects of this essential oil were tested against E. coli and S. aureus using agar disc diffusion method. The bacterial culture were exposed to five different concentration of essential oils: 25%, 50%, 75%, 100% and control (ethyl alcohol) in a completely randomized design in four replicates.

Results: The results obtained indicated that essential oil of C. citriodora leaves has antimicrobial activity against both E. coli and S. aureus. The diameter of zones of inhibition by the leaf extracts of C. citriodora was 13.3±2.0 – 35.4±5.1 mm and 12.1±1.9 – 32.7±5.1 mm, respectively, for E. coli and S. aureus. The results revealed that a more significant inhibition was observed with a higher essential oil concentration. Thus, with increasing essential oil concentration, an inhibitory effect on the growth of E. coli and S. aureus significantly increased. At low concentrations, a significant higher inhibitory effect was observed on the growth of microorganisms in comparison with those controls.

Conclusion: The results, therefore, suggests that characterization and isolation of the active phytoceutical(s) from essential oil of C. citriodora leaves may provide a valuable antimicrobial agent for counteracting infectious diseases caused by E. coli and S. aureus, which have developed resistance to antibiotics.