Screening of selected essential oils for antibacterial activity in vapour phase

The aim of this study was to identify antimicrobial properties of essential oils in vapour phase from selected species of spices, medicinal and aromatic plants. The essential oils, obtained from fresh plant materials by hydrodistillation, were selected either according to etnobotanical data or based on a chemotaxonomic approach. The tests for antimicrobial properties were carried out by the modified diffusion method for testing of essential oils in vapour phase [1]. The tests were performed against two Gram-positive (Listeria monocytogenes, Staphylococcus aureus) and 3 Gram-negative (Eschericia coli, Pseudomonas aeruginosa, Salmonella enteritids) food-borne bacteria. The results were expressed as minimum inhibitory dose (MID) in µl/cm³ of air. Thirteen of the 28 essential oils were active at least against one bacterial strain. The best results were exhibited by horse-radish (Armoracia rusticana, MID 0.0083µl/cm³) against all of the strains, garlic (Allium sativum, 0.0083–0.53µl/cm³) against all of the strains, oregano (Origanum vulgare, 0.066–0.13µl/cm³) against all of the strains except P. aeruginosa, which was not inhibited and thyme (Thymus vulgaris, 0.017–0.26µl/cm³) except P. aeruginosa. Among the others species interesting results were shown Nepeta x faassenii and Caryopteris x clandonensis (MID 0.53µl/cm³ against S. aureus), for which this is the first report of antibacterial activity. In conclusion, certain essential oils are highly effective in vapour phase and can be used in fight against food-borne bacterial pathogens.

Acknowledgements: Ministry of Education of the Czech Republic MSM 6046137305

References: [1] Lopez, P. et al. (2005) J. Agr. Food Chem. 53: 6939–6946.