In Vitro Antibacterial Activity of Thymus satureioides, Menthapulegium, and Origanumvulgare Essential Oils Against Escherichia coli Isolated from Raw Sheep Milk

This study aims to evaluate in vitro the antibacterial activity of essential oils extracted from Thymus satureioides, Mentha pulegium and Origanum vulgare against Esherichia coli isolated from raw sheep milk of Sardi breed using dilution technique in liquid medium in order to determine MIC and MBC and compared to the effectiveness of those extratcs on E. coli isolated from patients and sheep meat. The yields of essential oils obtained by steam distillation were determined relatively to the plant dry matter and each oil was analyzed by gas chromatography coupled to mass spectrometry (GC-MS) in order to determine its chemical composition. Results obtained showed that the most important yield was obtained with M. pulegium (3.2%) followed by T. satureioides (1.85%) and O. vulgare (1,6%). Essential oils tested proved a very significant antibacterial activity against Escherichia coli strains. The great effect was observed with T. satureioides followed by O. vulgare and M. pulegium from low concentrations. The determination of the Minimal Bactericidal Concentrations (MBCs) has shown that plants’ extracts studied have a bactericidal effect on all strains and their values in µg / ml are identical to those of the Minimal Inhibitory Concentrations (MICs). The results of the essential oils’ chemical compositions demonstrated that components of these oils are monoterpene oxygenated derivatives, monoterpene hydrocarbons and phenols. The great antibacterial activity, proved by essential oils tested during this research, opens up an area for the use of medicinal plants as preservatives in dairy industry and for therapeutic purposes.