The arbitrary use of antibiotics to prevent and treat diseases in aquatic animals has led to the emergence of antibiotic-resistant bacteria. For this reason, in many countries, very strict rules have been established regarding the use of antibiotics. One of the ways to solve this problem is to use food supplements such as probiotics, prebiotics and synbiotics, which have beneficial effects on the host's immunity and resistance to disease. Since the best probiotic for each organism is isolated from the digestive system of the same organism, in this, after separating, homogenizing and diluting the end part of the fish caught from the farms, the samples were cultured on plates containing MRS agar, M17 agar and MMRS agar culture medium and incobation. The formed colonies were examined in terms of morphological and biochemical characteristics, and gram-positive and catalase-negative isolates were selected for further experiments. Lactic acid bacteria isolates were screened based on their ability to grow in the presence of different acidity and bile salt and differences in biochemical properties, and then their resistance to probiotic properties such as resistance to different acidity and bile salt concentration and stomach simulation conditions were examined and screened. Finally, Antimicrobial effect of bacteria in the presence of glucose and inulin against the growth of pathogenic bacteria, their sensitivity to antibiotics and their growth stimulation by inulin were eva‎luated. The obtained bacteria were identified through 16S rDNA gene sequence analysis. The results showed that out of a total of 58 lactic acid bacteria isolates isolated from fish intestines, 36 isolates were different in terms of growth in the presence of different conditions of acidity and bile salts, as well as biochemical characteristics. Among the 36 isolates screened, most of them were resistant to different acidity conditions and 12 isolates were resistant to bile salts. Among these 12 isolates, six isolates were able to resist in the presence of the simulated conditions of the stomach. six bacterial isolates screened alone have more antimicrobial effect against pathogenic bacteria Edwardsiella tarda and Aeromonas hydrophila compared to growth with inulin, Compared to the glucose, inulin had a significant difference on stimulation growth and survival of bacteria and compared to antibiotics, they showed different results. All six isolates were identified by molecular method, Lactobacillus sakei, which were isolated for the first time in Iran from the intestine of rainbow trout. The results of this study confirm the probiotic potential of, Lactobacillus sakei and its antimicrobial effect against the growth of pathogenic bacteria and the use of inulin with, Lactobacillus sakei as a synbiotic combination.

صبيحه سليمانيان‌زاد، امير حسين جلالي

نفيسه سلطاني‌زاده، امير حسين مهدوي