Project description:The Escherichia coli strain Nissle 1917 (EcN) is used as a probiotic for the treatment of certain gastrointestinal diseases in several European and non-European countries. In vitro studies showed EcN to efficiently inhibit the production of Shiga toxin (Stx) by Stx producing E. coli (STEC) such as Enterohemorrhagic E. coli (EHEC). The occurrence of the latest EHEC serotype (O104:H4) responsible for the great outbreak in 2011 in Germany was due to the infection of an enteroaggregative E. coli by a Stx 2-encoding lambdoid phage turning this E. coli into a lysogenic and subsequently into a Stx producing strain. Since EHEC infected persons are not recommended to be treated with antibiotics, EcN might be an alternative medication. However, because a harmless E. coli strain might be converted into a Stx-producer after becoming host to a stx encoding prophage, we tested EcN for stx-phage genome integration. Our experiments revealed the resistance of EcN towards not only stx-phages but also against the lambda phage. This resistance was not based on the lack of or by mutated phage receptors. Rather the expression of certain genes (superinfection exclusion B (sieB) and a phage repressor (pr) gene) of a defective prophage of EcN was involved in the complete resistance of EcN to infection by the stx- and lambda phage. Obviously, EcN cannot be turned into a Stx producer. Furthermore, we observed EcN to inactivate phages and thereby to protect E. coli K-12 strains against infection by stx- as well as lambda-phages. Inactivation of lambda-phages was due to binding of lambda-phages to LamB of EcN whereas inactivation of stx-phages was caused by a thermostable protein of EcN. These properties together with its ability to inhibit Stx production make EcN a good candidate for the prevention of illness caused by EHEC and probably for the treatment of already infected people.
Project description:Shiga toxin type 2 (Stx2) is the main virulence factor produced by Stx-producing Escherichia coli (STEC) responsible for hemorrhagic colitis and the life-threatening sequela hemolytic uremic syndrome.
Project description:Enterohemorrhagic Escherichia coli (EHEC) is a food-borne pathogen that causes diarrheal disease and the potentially lethal hemolytic uremic syndrome. Here, we used an infant rabbit model of EHEC infection that recapitulates many aspects of human intestinal disease to comprehensively assess the host colonic epithelial and lamina propria cell transcriptional responses to EHEC infection. Furthermore, comparisons of colonic pathology and intestinal transcriptomic profiles in animals infected with EHEC strains containing or lacking Shiga toxins (∆∆stx) were carried out to investigate how these potent toxins shape the host response to the pathogen. We found that Stx is required for severe, multi-focal hemorrhage and extensive apoptosis in the colon. RNA-sequencing revealed that EHEC infection elicits a robust innate immune response in the colonic epithelium that is dramatically shaped by Stx. Over 1400 genes were differentially expressed in animals infected with WT versus ∆∆stx EHEC strains. Several pathways linked to innate immune responses were dependent on Stx. Upregulated genes in the presence of toxin included cytokines IL23a and CXCL8, as well as F3, the gene encoding the coagulation initiator Tissue Factor. RNA FISH revealed that these elevated transcripts were found almost exclusively in epithelial cells, suggesting that Stx remodels the transcriptional profile of the epithelium. Collectively, these findings reveal that Stx potently modulates the innate immune response to EHEC in the intestine, and suggest that Stx drives the response to infection towards type 3 immunity.
Project description:A food-borne outbreak of haemorrhagic colitis (HC) and HUS caused by E. coli O103:H25 occurred in Norway, 2006. The outbreak included 17 registered cases, of which 10 developed HUS. The aim of this study was to characterize two E. coli O103:H25 isolates from this outbreak. Only one of the isolates carry the stx2 gene (by PCR). Since they have the same typing profile by typing method MLVA, we expect the isolates to have identical gene content except from an Stx2-encoding phage. Therefore, we further investigate whether the Stx2-encoding phage has any impact on the gene expression. Keywords: mixed, gene expression, comparative genomic hybridization Triplicate samples of mRNA from a test strain O157:H7 EDL933 and two outbreak strains - one Stx positive and one stx negative were co-hybridized with genomic DNA from the same strain. Triplicate samples of the Stx positive strain grown at acidic conditions was also co-hybridized with genomic DNA from the Stx positive strain. Genomic DNA for each strain is technical replicates only.
Project description:Changes in endothelial phenotype induced by E. coli-derived Shiga toxins (Stx) are believed to play a critical role in the pathogenesis of hemolytic uremic syndrome. Stx inactivate host ribosomes, but also alter gene expression at concentrations that minimally affect global protein synthesis. The effect of Stx on the gene expression profile of human microvascular endothelial cells was examined using the Affymetrix HG-U133A platform. Data were processed using 13 different methods and revealed 369 unique differentially expressed genes, 318 of which were up-regulated and 51 of which were down-regulated. These studies implicated activation of the CXCR4/CXCR7/SDF-1 chemokine pathway in Stx-mediated pathogenesis. Primary human dermal microvascular endothelial cells were treated with vehicle or Shiga toxin (10 fM, 24 h, n = 6) and changes in steady-state mRNA levels were determined by hybridization to Affymetrix HG-U133A arrays