antagonistic activity of probiotic bacteria isolated from traditional dairy products against e. coli o157:h7

Background: probiotics are living microorganisms that have useful effects on health of digestive system when acquired in a defined dosage. e. coli o157:h7 is known as one of the most important agents of diarrhea in developing countries. therefore, attention to the treatment of such gastrointestinal disease is essential. the aim of this study was to determine antagonistic activity of food born lactobacilli against e. coli o157:h7.methods: lactobacilli were isolated from traditional dairy products (yogurt and buttermilk samples). then, they were characterized using biochemical and molecular tests. bifidobacterium bifidum ptcc 1644 was obtained from the microbial collection of iranian research organization for science and technology in lyophilized form. similarly, e. coli o157:h7 ptcc12900 was obtained from faculty of veterinary medicine university of tehran. the antagonistic activity of probiotics supernatants against e. coli o157:h7 was investigated using the disk diffusion agar, well diffusion agar and pour plate methods.results: the isolates were characterized as lactobacillus plantarum and lactobacillus fermentum. all isolates showed antagonistic activities against e. coli o157:h7 in all of the three methods, where the activity of l. plantarum and b. bidifum ptcc 1644 was greater than that of l. fermentum.conclusion: metabolites produced by the probiotic bacteria are able to inhibit the growth of e. coli o157:h7. this can be an important solution for the prevention and treatment of e. coli o157:h7 infection and ultimately improve human health.