Evaluation of the effect of Saccharomyces cerevisiae on the expression of enterotoxin genes in Escherichia coli O157: H7 (EHEC) and Escherichia coli H10407 (ETEC).

Enterotoxigenic (ETEC) and enterohemorrhagic Escherichia coli (EHEC) are the most important intestinal pathogens. Probiotics play an effective role in reducing the expression of virulence factor genes in intestinal pathogenic bacteria. The aim of the present study is to investigate the effect of probiotic Saccharomyces cerevisiae S3 on the expression of enterotoxin genes in both ETEC and EHEC. Supernatant and lysate of S. cerevisiae S3 are prepared. Subminimal inhibitory concentrations (sub-MIC) of supernatant and lysate are individually exerted to O157: H7 and H10407. The genes' expression of enterotoxins (elt, est, stx1, and stx2) are then determined using real-time PCR technique. The results showed, the yeast supernatant could decrease the expression of the elt gene in ETEC and that of stx1 in EHEC. Of note, in other cases, stx1 and est genes' expression increased. The lysate had no inhibitory effect on the expressions of elt, est, and stx2 genes, but it increased the expression of genes in both ETEC and EHEC. Lysate extract only decreased the expression of stx1 in O157: H7. Our study shows some interesting results regarding the effectiveness of the compounds produced by S. cerevisiae S3 in the expressions of toxin genes in both ETEC and EHEC. We recommend more similar studies be performed in this regard.