Presentation Abstract

Abstract Title: Role of the Intestinal Microbiota in Disease Due to Enterohemorrhagic E. coli in Germ Free Mice
Author Block: K. A. EATON1, K. A. EATON1, B. M. McGill1, K. G. Skinner1, E. C. Martens1, C. A. Fontaine1, R. A. Britton2;
1Univ. of Michigan, ANN ARBOR, MI, 2Michigan State Univ., East Lansing, MI.
Presentation Number: 1576
Poster Board Number: 1576
Keywords: Shiga-toxigenic Escherichia coli,intestinal microbiota,Animal Model
Abstract: Background: Enterohemorrhagic Escherichia coli (EHEC) does not colonize conventional mice, but does colonize germfree and antibiotic-treated mice. The mechanisms by which intestinal microbiota confer colonization and disease resistance are not known. Our goal was to evaluate specific microbial species, strains, and communities for the ability to suppress EHEC colonization, modify Shigatoxin production in vivo, and/or ameliorate disease in mice. Methods: Germfree Swiss-Webster mice were co-inoculated with EHEC O157:H7 (strain EDL933 or 185), and either a non-pathogenic E. coli strain (HS, 183, or FI-29), an 11-strain bacterial cocktail (E. coli HS, Barnesiella intestinihominis, Bacteroides thetaiotaomicron, B. vulgatus, B. uniformis, Parabacteroides distasonis, Eubacterium rectale, Faecalibacterium prausnitzii, Roseburia inulinovorans, R. intestinalis, and Bifidobacterium longum), Segmented, Filamentous Bacteria (SFB), or a human intestinal microbial community. EHEC colonization was quantified by culture on sorbitol-MacConkey agar, colon and renal lesions were quantified morphologically, and Shigatoxin in cecal contents was quantified by ELISA and RT-PCR. Results: Marked suppression of EHEC colonization by the human microbiota was associated with complete absence of disease. However, an 11-species bacterial community representing the common enteric genera only partially suppressed colonization, but completely eliminated disease. Non-pathogenic E. coli FI-29 or HS did not alter colonization or stx2 gene expression but completely eliminated disease in association with complete adsorption of luminal Stx2. In contrast, E. coli strain 183 failed to suppress colonization, disease, or Stx2 level. SFB did not alter either colonization or disease. Conclusions: Prevention of disease by non-pathogenic bacteria is associated with absence of luminal Stx2, but does not depend on suppression of either EHEC colonization or stx2 gene expression.