In this study Bacillus subtilis is used for control of streptococcosis with the agent of Streptococcus iniae in Rainbow trout. The experience was carried out in 2 groups (Control and Treatment) and 3 replicates. In Control group, probiotic was not applied in diet but in Treatment group, Bacillus subtilis was administered in feed at a concentration of 10 7 cells g-1. In the day of forty five, 0.1 ml intraperitoneally injection of S.iniae with 2×10 7 cells ml-1 dosage was done for both of groups and were checked for the rest of the survey duration (2 weeks). At the end of the time which took about two months, blood samples were caught for biochemical experiments for realizing the effect of B.subtilis feeding on resistance of fish against S.iniae infection. After injection of S.iniae, there was no significant difference among Control(C) and Treatment(T) groups considering parameters such as glucose and aspartate aminotransferase (p>0.05). But significant difference was seen in the serum total protein, serum albumin, IgM, lysozyme, 38 M. Kamgar, R. Pourgholam, M. Ghiasi and M. Ghane urea, Alanin aminotransferase and alkaline phosphatase in both groups (p<0.05). The serum total protein, serum albumin, IgM and lysozyme were higher in T group and urea, Alanin aminotransferase and alkaline phosphatase were lower in comparison with the control. The results of the present study indicate that B.subtilis can be used as an agent for the control of streptococcosis in Rainbow trout hatchery and culture farms for decreasing economical disasters.

No abstract

Background: Escherichia coli infections are one of the major health problems in many countries. The emergence of antibiotic resistance has complicated the treatment of infections caused by this microorganism. Today, researchers are focusing on novel approaches for the treatment of E. coli infections among which is using spore-forming probiotics for their high stability in the harsh gastrointestinal (GIT) environment. Results: This study screened the potential of B. coagulans and B. subtilis to inhibit the expression of flu, eae, luxS, and ctxM genes in 40 E. coli isolated from a total of 300 fecal samples of patients suffering from diarrhea from August 2018 to January 2019. For this purpose, first the presence of these genes was confirmed in the isolates using the PCR method. Then, the standard strains and broiler-derived B. subtilis and B. coagulans were used to screen their ability to tolerate low pH, bile salts, and gastric enzymes. After confirming their ability to survive under the simulant gastric environment, they were cocultured with E. coli isolates (n=4) harboring all the flu, eae, luxS, and ctxM genes. After reaching the logarithmic growth phase, the expression levels of flu, eae, luxS, and ctxM genes were determined using the real-time PCR methods. According to the results, there was a statistically significant relationship between the exposure of E. coli with commercial and broiler-derived spore-forming probiotics and the reduced expression of these genes. Conclusion: The broiler-derived isolates had a greater capacity to decrease the expression of these genes compared to the standard strains, proposing their adoption for dietary supplementations. However, more studies are required to study the effects of these spore-forming bacteria on E. coli infections in vivo and their possible influence on lactose tolerance, nutritional absorption, and reduced cholesterol levels.