Evaluation of the inhibitory activity of shiga like toxin producing Escherichia coli by Lactobacillus spp. isolated from pigs

Abstract

Introduction: Foodborne diseases represent health and economic problems of relevance in the world. Symptoms vary depending on the causal agent, the dose of intake and the age of the group affected. Bacteria most implicated are Shiga toxinproducing Escherichia coli (STEC). To reduce the risk of infection by pathogen is necessary a strict microbiological monitoring throughout the food production chain. One strategy is the use of biopreservation systems as lactic acid bacteria or their metabolites. The genus Lactobacillus is of interest as biotechnological applications and by their probiotic properties. Usually, these strains are isolated from humans because of their greater ability to adhere to and colonize the intestinal epithelium. However studies have shown that strains of Lactobacillus isolated from animals also have beneficial effects on human. Through this study, we determinated the inhibitory activity of Lactobacillus spp. isolated from pigs on EDL933 STEC reference strain. Methods: Samples were taken by swabs from pig, carcasses and pork cuts and incubated in MRS broth at 37ºC for 48h. Forty five percent of the strains were characterized by biochemical tests as lactobacilli. These strains were individually inoculated on MRS agar plates and incubated at 37ºC for 48h, then they were exposed to chloroform vapors. Then the plates were overlaid with LB agar containing E. coli EDL933 (106 ufc/ml) and incubated overnight at 37 ºC. Finally, the inhibitory activity was evaluated by observing the translucent halo around the colony. Results and discussion: Sixty three percent of the strains developed a halo greater than 1 mm. This indicates that the Lactobacillus have antagonistic properties against this pathogen. Implications: These results show that lactic acid bacteria strains isolated from pigs can become a useful biotechnological tool for controlling E. coli O157:H7, it generates alternatives for producing foods naturally protected and improve the microbiological quality in the food industry.