Investigation of antibacterial effects of garlic (Allium sativum), mint (Menthe spp.) and onion (Allium cepa) herbal extracts on Escherichia coli isolated from broiler chickens Ahmad Ziarlarimi1*, Mehrdad Irani2, Shahabodin Gharahveysi3 and Zahra Rahmani4
1,2,3
Department of Animal Science, Qaemshahr Branch, Islamic Azad University, Qaemshahr, Iran.
4
Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
Accepted 24 March, 2011
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 effects
INTRODUCTION
Pharmaceutical plants have been commonly used by humans long ago and the consumption rate has changed based on the occasion and the requirement of the time.
In recent years, Iranians and other people from around the world have shown a tremendous interest in these plants as a way to cure their illnesses. Today, there have been several attempts to develop these plants and the derivatives because the ever-increasing usage of the chemical drugs has led to serious problems and created resistant types of insensitive micro-organisms, while herbal drugs bring about fewer side effects because the biological balance. The herbal extracts are either used
alone as the drug itself or constitute a part of the drug.
Escherichia coli is one of the first intestinal bacilli which has been cultured and is the intestinal flora in humans and animals. It is a facultative anaerobic bacterium that grows on certain mediums especially eosin methylene blue agar (EMBA) with metallic sheen colonies. This organism grows at the range of 10 to 46°C but optimal temperature is 37°C. Most of the strains of E. coli are killed at 60°C in 30 s. But some resistant strains are available. This organism, in different conditions, can act as a pathogenic bacterium, especially in secondary infections.
Most essential oils consist of mixtures of compounds such as phenolics and polyphenols, terpenoides, saponins, quinines, esters, flavones, flavonoids, tannins, alkaloids and nonvolatile residues; and their chemical composition and concentration of compounds is variable.
These components have many effects as antimicrobial, stimulating animal digestive systems, antioxidants,
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Table 1. The mean diameter (mm) of zones of inhibition of herbal extracts against E. coli activity.
