Comparative evaluation of the antibacterial activity of Dill (Anethum graveolen L.) and garden Thyme (Thymus vulgaris) against of Salmonella Typhimurium (ATCC= 14028)

Salmonellosis is one of the most important common diseases of livestock and humans worldwide. With the prevalence of antibiotic resistance, the tendency to use medicinal plants to control microorganisms has increased. The aim of this research was to investigate the antibacterial effects of the essential oils of Thymus vulgaris and salmonella typhimurium (ATCC=14028). For this purpose, first, the essential oils of the mentioned plants were extracted by steam distillation using a Clovenger machine. Then, using the microdilution broth method, the Minimum Inhibitory Concentration (MIC) and the Minimum Bactericidal Concentration (MBC) of essential oils alone and in combination, as well as drug sensitivity or resistance testing based on the well diffusion method in agar against the standard strain of Salmonella typhimurium bacteria, were determined in comparison with three common antibiotics in veterinary medicine. The MIC was calculated for thyme (0.25), mixed essential oil (0.50), doxycycline (0.0078) and oxytetracycline (<0.00195) μg/ml. The MBC for them was 0.25, 0.50, 0.0156 and >0.00195 respectively. Dill essential oil and erythromycin antibiotic had no antimicrobial effect against Salmonella typhimurium. The highest effect was related to oxytetracycline (with a growth inhibition diameter of 27 mm) and the lowest effect was related to thyme essential oil (with a growth inhibition diameter of 10 mm). Unlike dill essential oil, garden thyme essential oil has a significant antibacterial effect.