Aims Over the last few years, there has been an increasing interest in the use of natural substances for promoting human and animal health. Antibiotic resistance, enhanced by excessive use of antibiotics, has encouraged human and animal health authorities to consider and employ alternative approaches, including herbal and botanical medicine to combat invading microorganisms. Herein, the essential oils of Thymus vulgaris, Allium cepa, Allium sativum, Eucalyptus globulus, Salvia officinalis, Dianthus caryophyllus, Mentha spicata and Mentha piperita, were evaluated for their antibacterial activities against standard Escherichia coli O157:H7 by disk diffusion method. Main methods Minimum Inhibitory Concentrations (MICs) and Minimum Bactericidal Concentrations (MBCs) were assessed via microdilution assay. In the next step, two combinations of these essential oils were formulated. Their in-vitro antibacterial effects were evaluated and compared with a commercially available herbal drug containing T. vulgaris essential oil. Key findings According to the results, the two new formulated essential oil combinations had more potent antibacterial effects against E. coli when compared to the commercial herbal drug. Significance The presented data indicate the potential antibacterial activity of these newly formulated essential oil remedies to be employed in the poultry industry in the fight against colibacillosis, although this claim has to be examined in experimental and clinical trials.

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