Dataset Information

Octamer-based genome scanning distinguishes a unique subpopulation of Escherichia coli O157:H7 strains in cattle.

ABSTRACT: Multilocus-genotyping methods have shown that Escherichia coli O157:H7 is a geographically disseminated clone. However, high-resolution methods such as pulse-field gel electrophoresis demonstrate significant genomic diversity among different isolates. To assess the genetic relationship of human and bovine isolates of E. coli O157:H7 in detail, we have developed an octamer-based genome-scanning methodology, which compares the distance between over-represented, strand-biased octamers that occur in the genome. Comparison of octamer-based genome-scanning products derived from >1 megabase of the genome demonstrated the existence of two distinct lineages of E. coli O157:H7 that are disseminated within the United States. Human and bovine isolates are nonrandomly distributed among the lineages, suggesting that one of these lineages may be less virulent for humans or may not be efficiently transmitted to humans from bovine sources. Restriction fragment length polymorphism analysis with lambdoid phage genomes indicates that phage-mediated events are associated with divergence of the lineages, thereby providing one explanation for the degree of diversity that is observed among E. coli O157:H7 by other molecular-fingerprinting methods.

SUBMITTER: Kim J

PROVIDER: S-EPMC23940 | biostudies-literature | 1999 Nov

REPOSITORIES: biostudies-literature

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Octamer-based genome scanning distinguishes a unique subpopulation of Escherichia coli O157:H7 strains in cattle.

Kim J J Nietfeldt J J Benson A K AK

Proceedings of the National Academy of Sciences of the United States of America 19991101 23

Multilocus-genotyping methods have shown that Escherichia coli O157:H7 is a geographically disseminated clone. However, high-resolution methods such as pulse-field gel electrophoresis demonstrate significant genomic diversity among different isolates. To assess the genetic relationship of human and bovine isolates of E. coli O157:H7 in detail, we have developed an octamer-based genome-scanning methodology, which compares the distance between over-represented, strand-biased octamers that occur in ...[more]

PMID: 10557313

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Project description:Vaccination-induced Escherichia coli O157:H7-specific immune responses have been shown to reduce E. coli O157:H7 shedding in cattle. Although E. coli O157:H7 colonization is correlated with perturbations in intestinal microbial diversity, it is not yet known whether vaccination against E. coli O157:H7 could cause shifts in bovine intestinal microbiota. To understand the impact of E. coli O157:H7 vaccination and colonization on intestinal microbial diversity, cattle were vaccinated with two doses of different E. coli O157:H7 vaccine formulations. Six weeks post-vaccination, the two vaccinated groups (Vx-Ch) and one non-vaccinated group (NonVx-Ch) were orally challenged with E. coli O157:H7. Another group was neither vaccinated nor challenged (NonVx-NonCh). Fecal microbiota analysis over a 30-day period indicated a significant (FDR corrected, p <0.05) association of bacterial community structure with vaccination until E. coli O157:H7 challenge. Shannon diversity index and species richness were significantly lower in vaccinated compared to non-vaccinated groups after E. coli O157:H7 challenge (p < 0.05). The Firmicutes:Bacteroidetes ratio (p > 0.05) was not associated with vaccination but the relative abundance of Proteobacteria was significantly lower (p < 0.05) in vaccinated calves after E. coli O157:H7 challenge. Similarly, Vx-Ch calves had higher relative abundance of Paeniclostridium spp. and Christenellaceae R7 group while Campylobacter spp., and Sutterella spp. were more abundant in NonVx-Ch group post-E. coli O157:H7 challenge. Only Vx-Ch calves had significantly higher (p < 0.001) E. coli O157:H7-specific serum IgG but no detectable E. coli O157:H7-specific IgA. However, E. coli O157:H7-specific IL-10-producing T cells were detected in vaccinated animals prior to challenge, but IFN-γ-producing T cells were not detected. Neither E. coli O157:H7-specific IgG nor IgA were detected in blood or feces, respectively, of NonVx-Ch and NonVx-NonCh groups prior to or post vaccinations. Both Vx-Ch and NonVx-Ch animals shed detectable levels of challenge strain during the course of the study. Despite the lack of protection with the vaccine formulations there were detectable shifts in the microbiota of vaccinated animals before and after challenge with E. coli O157:H7.

Dataset Information

Octamer-based genome scanning distinguishes a unique subpopulation of Escherichia coli O157:H7 strains in cattle.

Publications

Octamer-based genome scanning distinguishes a unique subpopulation of Escherichia coli O157:H7 strains in cattle.

Similar Datasets

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