BackgroundProbiotics are live microorganisms which are beneficial bacteria that are normal flora of the digestive system which, in determined amounts, show beneficial effects on host health, and can balance gastrointestinal microflora. Digestive tract diseases such as diarrhea are one of the major causes of child mortality in developing countries. Different pathotypes of Escherichia coli cause diarrhea that affects children, therefore reduction of these colonization strains in humans or animals can decline gastrointestinal disorders such as diarrhea.ObjectiveThe aim of this study was to determine the antimicrobial effect of probiotic bacterial strains isolated from different natural sources against 4 pathotypes of pathogenic E. coli using disk and well diffusion methods.MethodsThis cross-sectional study was conducted from December 2013 to July 2014 on Martyr Chamran University in Ahwaz city. A total of 13 probiotic colonies isolated from 20 samples of traditional dairy products including yogurt, cheese and milk, and 20 samples of vegetables including carrots and cabbages (red and white), of which 5 isolates were selected to determine the antimicrobial effect against 4 Escherichia coli pathotypes, randomly. The antimicrobial effect was evaluated using two methods: disk diffusion and well diffusion tests and measuring growth inhibition zones of probiotics against 4 pathotypes of pathogenic E. coli.ResultsObtained results showed growth inhibition effects of all 5 probiotic strains against Escherichia coli pathotypes in both used methods. But in comparison Lactobacillus plantarum had higher growth inhibitory effects in both methods.Conclusionresults of this study demonstrated high antimicrobial effect of probiotic bacteria against pathogenic Escherichia coli strains. It indicated a positive and beneficial role of probiotics in human health and prevention of illness.

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Background: Leptospirosis is a prevalent zoonotic disease caused by Leptospira interrogans bacterium. Despite the importance of this disease, traditional strategies including attenuated and inactivated vaccines have not been able to prevent leptospirosis. Objective: Hence, this study was designed to develop a novel poly-epitope fusion protein vaccine against leptospirosis. Results: To do so, the best epitopes of OmpA, LipL45, OmpL1, LipL41 and LipL21 proteins were predicted. Then, the best predicted epitopes were applied to assemble IFN-γ, MHC I binding, B cell, MHC II binding fragments, and heparin-binding hemagglutinin adhesion was used as a molecular adjuvant. After designing the vaccine, the most important features of it, including physicochemical parameters, protein structures and protein-protein interaction were evaluated. Finally, the nucleotide sequence of the designed vaccine was used for codon adaptation. The results showed that the designed vaccine was a stable protein with antigenicity of 0.913 which could dock to its receptor. The results also suggested that the nucleotide sequence of the designed vaccine could be expressed in prokaryotic system. Conclusion: Based on results of this study, it can be concluded that our designed vaccine can be a promising candidate to control leptospirosis.

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