Effects of antibacterial compound of Saccharomyces cerevisiae from koumiss on immune function and caecal microflora of mice challenged with pathogenic Escherichia coli O8

Anotace: The yeast Saccharomyces cerevisiae from koumiss has been shown to have antibacterial effects on Escherichia coli, possibly by producing antibacterial compound in metabolism; however, there is limited knowledge about its application in animal production. We therefore investigated the effects of an antibacterial compound of S. cerevisiae from koumiss on the immune function and caecal microflora of mice challenged with pathogenic Escherichia coli O8. Three groups were formed: negative control (NC), positive control (PC), and the antibacterial compound of S. cerevisiae at pH 2.0 (S2). Mice in the NC and PC groups were orally administered phosphate buffer solution (PBS) for 7 d. At 4 d, E. coli O8 was administered intraperitoneally in group PC. Mice in group S2 were first administered orally as mice in group NC, and subsequently intraperitoneally administered E. coli O8 as mice in group PC. Compared with the NC group, mice in the PC group displayed clinical symptoms and pathological changes in the small intestine. Small intestine villi in the S2 group also developed some histologically pathological changes but not as severe as in the PC group. Moreover, there was less mortality in the S2 group than in the PC group. In PC group, thymus indexes, immunoglobulin A (IgA) in serum and Bifidobacterium in caecum were decreased and E. coli in the caecum was increased. In the S2 group, CD8+ of T lymphocyte subsets in blood and Bifidobacterium in caecum were decreased, while spleen indexes, IgG, IgM in serum, and CD3+ of T lymphocyte subsets in blood were increased. This suggests that S2 can relieve clinical symptoms of mice challenged with pathogenic E. coli O8, enhance their immune function, and influence their caecal microflora. The study will provide a theoretical foundation for utilizing antibacterial compound of S. cerevisiae from koumiss for curative purposes.