chemical compositions and inhibitory effects of essential oils of turkish oregano (origanum minutiflorum o. schwarz & p. h. davis), bay laurel (laurus nobilis l.), spanish lavender (lavandula stoechas subsp. stoechas l.), and fennel (foeniculum vulgare mill.) on escherichia coli o157:h7, listeria monocytogenes, salmonella typhimurium, and staphylococcus aureus were determined. after the essential oils were applied on the foodborne pathogens at doses of 0 (control), 5, 10, 20, 30, 40, 50, and 80 microl/ml, the resultant numbers of cells surviving were counted. results revealed that all essential oils exhibited a very strong antibacterial activity against the tested bacteria (p < 0.05). gas chromatography-mass spectrophotometry analyses revealed that carvacrol (68.23%), 1,8-cineole (60.72%), fenchone (55.79%), and trans-anethole (85.63%) were the predominant constituents in turkish oregano, bay laurel, spanish lavender, and fennel essential oils, respectively.