Table of Contents
International Journal of Antibiotics
Volume 2014, Article ID 586252, 5 pages
Research Article

Comparative Evaluation of the Inhibitory Effect of Some Essential Oils with Antibiotics against Pseudomonas aeruginosa

1Department of Environmental Studies, Institute of Graduate Studies and Research, Alexandria University, Egypt
2Department of Food Microbiology, National Research Center, Dokki, Cairo, Egypt
3Department of Biotechnology, Institute of Graduate Studies and Research, Alexandria University, Egypt

Received 29 June 2014; Revised 24 September 2014; Accepted 24 September 2014; Published 1 October 2014

Academic Editor: Branka Bedenić

Copyright © 2014 Lobna El-Hosseiny et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Gas chromatography/mass spectroscopy analysis was performed to identify the chemical components of three extracted essential oils including thyme, marjoram, and sage. The antibacterial activity of the extracted essential oils against Pseudomonas aeruginosa (ATCC 9027) was investigated using disc diffusion assay, either alone or in combination with standard antibiotics (piperacillin, cefepime, meropenem, gentamicin, and norfloxacin). Results showed that the studied oils exhibited a variety of activities against the tested bacterium. Thyme oil was the most active followed by marjoram oil, whereas sage displayed no activity towards the tested organism. Thyme oil enhanced the antibacterial activity of cell wall targeting antibiotics (piperacillin, cefepime, and meropenem) by more than twofold. Marjoram oil potentiated the activity of all the tested antibiotics except norfloxacin. Sage, despite its inactivity against pseudomonas, synergistically enhanced the activity of piperacillin, meropenem, and gentamicin. Thyme essential oil, containing thymol as a major component (33.6%), exhibited higher activity alone or in combination with antibiotics than marjoram which contained alcoholic terpenes or sage essential oil that contained 1,8-cineole as its major component (29%). The investigated oils, as natural bioactive agents, may be used to enhance the activity of antibiotics towards pseudomonas.