Prophage Induction Is Enhanced and Required for Renal Disease and Lethality in an EHEC Mouse Model

Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, United States of America.
PLoS Pathogens (Impact Factor: 7.56). 03/2013; 9(3):e1003236. DOI: 10.1371/journal.ppat.1003236
Source: PubMed


Author Summary
Infection with Enterohemorrhagic E. coli (EHEC), and more recently with the Enteroaggregative E. coli strain O104:H4, is a significant health risk, causing bloody diarrhea, kidney failure, and even death. The virulence factor in these bacteria responsible for the severe outcomes is Shiga toxin (Stx). Genes encoding Stx are in the genome of bacterial viruses (prophages) on the pathogenic E. coli chromosomes. The prophage remains quiescent until damage to the bacterial chromosome occurs causing prophage gene expression (called induction), which leads to production of bacteriophages that are released into the environment. Because stx expression is controlled by the phage regulatory system, prophage induction leads additionally to production and release of Stx. This study provides conclusive evidence that in a mouse model of EHEC infection, induction of the prophage carrying the stx genes is specifically required for EHEC to cause disease and that the intestinal environment adds to the induction and therefore to the production of Stx. Similar events likely regulate Stx production and release by the Stx encoding phage in the O104:H4 strain. Controlling prophage induction offers a means to control EHEC infection.

Download full-text


Available from: Karen Beeri, Mar 03, 2015
  • Source
    • "The life cycle of prophages is controlled by phage repressor CI proteins in lambdoid phage (Ptashne and Hopkins, 1968). Mutations in the cI gene make a non-cleavable repressor and an uninducible 933W Stx2 prophage (Tyler et al., 2013). RecA can stimulate the self-cleavage of CI further allowing initiation of transcription from the early P L and P R promoters (Little, 2005). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Polynucleotide phosphorylase (PNPase) is reported to regulate virulence in Salmonella, Yersinia sp. and Campylobacter jejuni, yet its role in Escherichia coli O157:H7 has not been investigated. To gain insights into its roles in E. coli O157:H7 virulence, pnp deletion mutants were generated and the major virulence factors were compared to their parental wild type strains. Deletion of pnp in E. coli O157:H7 dramatically decreased stx2 mRNA expression and Stx2 protein production, and impaired lambdoid prophage activation in E. coli O157:H7. Quantitative PCR further confirmed that the Stx2 phage lytic growth was repressed by pnp deletion. Consistent with reduced Stx2 production and Stx2 phage activation, the transcriptional levels of genes involved in phage lysis and replication were down-regulated. In addition, disruption of pnp in E. coli O157:H7 decreased its adhesion to intestinal epithelial cells as well as cattle colonic explant tissues. On the other hand, PNPase inactivation in E. coli O157:H7 enhanced Tir protein content and the transcription of type three secretion system components, including genes encoding intimin, Tir, and EspB as well as locus of enterocyte and effacement positive regulator, Ler. Collectively, data indicate that PNPase has pleiotropic effects on the virulence of E. coli O157:H7.
    Full-text · Article · Sep 2015 · Frontiers in Microbiology
  • Source
    • "induction is critical to Stx gene expression and to the ability of STEC to cause disease (Tyler et al., 2013). The toxin genes are late-stage genes that are transcribed only during the lytic stage of the phage. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Shiga toxin-producing Escherichia coli (STEC) strains are responsible for a variety of clinical syndromes including bloody and non-bloody diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). Although multiple serotypes of STEC have been isolated from hemorrhagic colitis cases, E. coli O157:H7 is by far the most prevalent serotype associated with HUS. Shiga toxin is the major virulence factor of E. coli O157:H7 and is responsible for the more severe symptoms of the infection. However, the mechanisms involved in the pathogenesis of diarrhea mediated by Stx2 are not well known. In this study, we have determined the effects of E. coli O157:H7 strain 125/99 wild type (wt) on the human colonic mucosa mounted in an Ussing chamber. In response to 125/99wt, an inhibition of water absorption across human colonic mucosa was observed. Histological sections showed severe necrosis with detachment of the surface epithelium, mononuclear inflammatory infiltrate and loss of goblet cells after 1h of incubation with 125/99wt. These alterations were not observed with the isogenic mutant strain lacking stx2 or with the filter-sterilized culture supernatant from the 125/99wt strain. These results indicate that the cell damages in human colon are induced by Stx2, and that Stx2 production is increased by the interaction with bacterial cells. Identification of host cell-derived factors responsible for increasing Stx2 can lead to new strategies for modulating STEC infections. Copyright © 2015 Elsevier GmbH. All rights reserved.
    Full-text · Article · Mar 2015 · International journal of medical microbiology: IJMM
  • Source
    • "Analysis of colonoscopy biopsies have shown that the mucus of Crohn's disease patients was 30-fold enriched in virus-like particles (3 × 10 9 VLP/biopsy versus 10 8 for healthy controls (Lepage et al., 2008). Even in the absence of external signal or inflammation, the stx2 carrying E. coli prophage 933 W is more induced in the gut of monoxenic mice than in vitro (Tyler et al., 2013). In E. coli and Lactobacillus genomes, the vast majority of prophages are defective, indicating an active selection against prophages induction (Martin et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Metagenomic approaches applied to viruses have highlighted their prevalence in almost all microbial ecosystems investigated. In all ecosystems, notably those associated with humans or animals, the viral fraction is dominated by bacteriophages. Whether they contribute to dysbiosis, i.e., the departure from microbiota composition in symbiosis at equilibrium and entry into a state favoring human or animal disease is unknown at present. This review summarizes what has been learnt on phages associated with human and animal microbiota, and focuses on examples illustrating the several ways by which phages may contribute to a shift to pathogenesis, either by modifying population equilibrium, by horizontal transfer, or by modulating immunity.
    Full-text · Article · Mar 2014 · Frontiers in Cellular and Infection Microbiology
Show more