Nazila Eslami - Department of Biology, Faculty of Basic Sciences, Islamic Azad University of Tabriz, Tabriz, Iran
Younes Anzabi - Department of Pathobiology, Faculty of Veterinary Medicine, Tabriz Medical Sciences, Islamic Azad University, Tabriz, Iran.
Mir Alireza Nourazar - Department of Basic Sciences, Faculty of Veterinary Medicine, Tabriz Medical Sciences, Islamic Azad University, Tabriz, Iran.

Gastrointestinal tract infection with serotypes of Salmonella is common worldwide, and its treatment with antibiotics leads to problems such as drug resistance and drug side effects. With the spread of antibiotic resistance, the desire to use medicinal plants to control microorganisms has increased. The use of medicinal plants can be a solution to this problem. This experimental study aimed to investigate the antimicrobial activity of Thyme essential oil compared to two antibiotics, doxycycline, and oxytetracycline, in an animal model. So, ۳۶ pieces of ۱۴-day-old broilers of the Ross breed were used in ۶ groups of ۶. The broilers were infected with Salmonella Typhimurium (ATCC۱۴۰۲۸). After extracting the essential oil from thyme and analyzing by GC-MS, the minimum inhibitory concentration (MIC) of its growth and antibiotic was determined by broth microdilution method, and finally, the broilers were treated by gavage for seven days, twice every day with a time interval of ۱۲ hours.  To check the effectiveness of antibiotics and essential oils, broiler feces were cultured daily, and the number of salmonella colonies grown was counted. The findings were analyzed with SPSS ۲۶ software and a two-way analysis of variance. The GC-MS analysis of T. vulgaris essential oil showed the presence of ۱۲ chemical compounds among which thymol, m-Thymol, p-cymene, and carvacrol were major. The results showed that there is a significant difference between the groups in terms of reducing the number of bacteria, but there is no significant difference between the times. Both thyme essential oil and doxycycline and oxytetracycline antibiotics reduced the colonization and finally stopped the excretion of Salmonella Typhimurium in the feces of broiler chickens.

Antibiotic Resistance, Broiler, Salmonella Typhimurium, Thyme essential oil, GC-MS