Antimicrobial Effects of Four Lactobacilli Strains Isolated from Yoghurt against Escherichia Coli O157:H7

This study aimed to isolate L actobacillus species from yoghurt and to evaluate its antimicrobial activity against enterohemorrhagic E scherichia coli O 157: H 7. After incubation of different yoghurt samples in MRS (de M an, R ogosa and S harpe) agar at 37 C under anaerobic conditions, four L actobacillus species, L . casei , L . acidophilus, L . helveticus and L . delbrueckii ssp. bulgaricus were identified. Standard growth curves of E . coli O 157: H 7 in proximity with lactobacilli test strains were obtained. The antibacterial effects of lactobacilli cell debris and culture supernatant against E . coli O 157: H 7 were determined. The results showed that the antibacterial effects of culture supernatant were stable at different temperature conditions (56–100C) for 30 and 60 min; also, it was stable at pH 3–10. With regard to the antibacterial effect of the lactobacilli strains in this study, they may help in the treatment of E . coli O 157: H 7‐associated diseases and can be applied as a biological preservative in the food industry. Practical Applications In recent years, foodborne diseases become a health problem in most of the population. One of the most important etiologic agents of such diseases is E scherichia coli O 157: H 7, which can be transmitted through eating undercooked infected meat and leads to hemorrhagic diarrhea and kidney failure. There is increasing evidence that lactobacilli bacteria produce potential agents ( H 2 O 2 , small organic compounds, lactic acid, etc.) that can inhibit growths of some invasive foodborne bacteria, such as enterohemorrhagic E . coli . The results of this study also confirmed these reports and showed that the use of lactobacilli bacteria is a promising way to prevent the infection of E . coli O 157: H 7; also, they can be used as a biological preservative in the food industry.