Summary: | 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,
36 pieces of 14-day-old broilers of the Ross breed were used in 6 groups of 6. The broilers were infected with
Salmonella Typhimurium (ATCC14028). After extracting the essential oil from thyme and analyzing by GCMS, 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 12 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 26 software and a two-way analysis of variance. The GC-MS analysis of T. vulgaris essential oil showed
the presence of 12 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.
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