Investigation of antibacterial effects of garlic (Allium sativum), mint (Menthe spp.) and onion (Allium cepa) herbal extracts on Escherichia coli isolated from broiler chickens

This study was done to determine minimum inhibitory concentration (MIC) of the aqueous extracts of garlic (Allium sativum), mint (Menthe spp.) and onion (Allium cepa) in in vitro conditions against the Escherichia coli isolated from broiler chickens. E. coli was isolated from the infected tissues of the chickens which were suspected of Colibacillus infection. In this study, distilled water, phenol phenicol and floxacin antibiotics were used as control. E. coli was sensitive to antibiotics, but distilled water had no inhibitory effect on the activity of E. coli. In this experiment, each of the aqueous extracts was prepared by using distilled water in 6 concentrations: 0.5, 1, 2.5, 5, 10 and 20%, and was poured into the cavities in nutrient agar medium, and then the plates were kept in incubator at 37°C for 24 h. The results indicated that MIC of the garlic aqueous extract was 5%, but E. coli was resistant to the aqueous extracts of onion and mint.Key words: Herbal extracts, garlic, onion, mint, Escherichia coli, broiler chickens, minimum inhibitory concentration, antibacterial effect