The purpose of our work was to determine antibacterial activity of essential oils and hydrosols made of summer savory (Satureja hortensis), laurel (Laurus nobilis), oregano (Origanum vulgare), Greek basil (Ocimum basilicum) and rosemary (Rosmarinus officinalis) against Escherichia coli and Staphylococcus aureus. During the work we decided to include also the hydrosol of sea algae (Laminaria digitata) and ethanolic extract of spelt (Triticum aestivum ssp. spelta). The main method we used to determine antibacterial activity of the substances was broth microdilution method. To get the precise minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) we performed the plate count method. For E. coli MIC values for essential oils were from 1.56 mg/ml to 6.25 mg/ml, and MBC values from 1.56 mg/ml to 12.5 mg/ml. The essential oil of oregano showed the best antibacterial activity with the lowest MIC of 1.56 mg/ml for E. coli and 0.78 mg/ml for S. aureus. In a concentration of 50 %, hydrosols did not show antibacterial activity, while 75 % hydrosols of summer savory and oregano did inhibit the growth of bacteria. As well did the 100 % hydrosol of rosemary. Hydrosols of laurel and Greek basil did not show antibacterial activity. The extract of spelt tested directly in triptic soy broth (TSB) did not inhibit growth of E. coli, but showed antibacterial activity against S. aureus. The extract of spelt diluted in ethanol and then tested in TSB inhibited growth of both tested bacteria. In this study we proved that essential oils and hydrosols do have a potential to inhibit the growth of bacteria, and that their activity differs due to plant sort. Overall, essential oils are more effective against bacteria than hydrosols. We can also confirm that Gram positive bacteria are more susceptible to essential oils and hydrosols than Gram negative bacteria.
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