In vitro control of multiplication of some food-associated bacteria by thyme, rosemary and sage isolates

Antibacterial activity of thyme, rosemary and sage isolates obtained by supercritical fluid extraction and hydrodistillation was investigated on Geobacillus stearotermophillus, Bacillus cereus, Bacillus subtilis var. niger, Enterococcus faecium, Salmonella enteritidis and Escherichia coli strains. Bacillus species were the most susceptible to all tested isolates. The thyme isolates showed the strongest antibacterial activity against tested bacteria with MIC values of 40-640 mu g/ml, followed by rosemary (MIC = 320-1280 mu g/ml) and sage (MIC = 160-2560 mu g/ml) isolates. Therefore, the antibacterial activity of the most abundant components found in the thyme isolates, thymol, p-cymene and their mixture was investigated as well. The thyme isolates, especially supercritical extract, showed stronger antibacterial activity against Bacillus strains compared to the single components and their mixture, which indicated synergetic effect of the other components. Results of this study indicated thyme as a valuable source of natural antibacterial agents and supercritical fluid extraction as an efficient isolation method.