A New Murine Model For Enterohemorrhagic Escherichia coli Infection Reveals That Actin Pedestal Formation Facilitates Mucosal Colonization and Lethal Disease: A Dissertation
Faculty Advisor
John M. Leong M.D., Ph.D.Academic Program
Molecular Genetics and MicrobiologyUMass Chan Affiliations
Molecular Genetics and MicrobiologyDocument Type
Doctoral DissertationPublication Date
2012-03-28Keywords
Enterohemorrhagic Escherichia coliEscherichia coli Infections
Hemolytic-Uremic Syndrome
Shiga-Toxigenic Escherichia coli
Shiga Toxin
Citrobacter rodentium
Adhesins
Bacterial
Escherichia coli Proteins
Amino Acids, Peptides, and ProteinsAnimal Experimentation and ResearchBacteriaBacterial Infections and MycosesBiological FactorsEnzymes and CoenzymesFemale Urogenital Diseases and Pregnancy ComplicationsHemic and Lymphatic DiseasesImmunology and Infectious DiseaseMale Urogenital Diseases
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Enterohemorrhagic Escherichia coli (EHEC) colonizes the intestine and produces the phage-encoded Shiga toxin (Stx) which is absorbed systemically and can lead to hemolytic uremic syndrome (HUS) characterized by hemolytic anemia, thrombocytopenia, and renal failure. EHEC, and two related pathogens, Enteropathogenic E. coli (EPEC), and the murine pathogen, Citrobacter rodentium, are attaching and effacing (AE) pathogens that intimately adhere to enterocytes and form actin “pedestals” beneath bound bacteria. The actin pedestal, because it is a unique characteristic of AE pathogens, has been the subject of intense study for over 20 years. Investigations into the mechanism of pedestal formation have revealed that to generate AE lesions, EHEC injects the type III effector, Tir, into mammalian cells, which functions as a receptor for the bacterial adhesin intimin. Tir-intimin binding then triggers a signaling cascade leading to pedestal formation. In spite of these mechanistic insights, the role of intimin and pedestal formation in EHEC disease remains unclear, in part because of the paucity of murine models for EHEC infection. We found that the pathogenic significance of EHEC Stx, Tir, and intimin, as well as the actin assembly triggered by the interaction of the latter two factors, could be productively assessed during murine infection by recombinant C. rodentium expressing EHEC virulence factors. Here we show that EHEC intimin was able to promote colonization of C. rodentium in conventional mice. Additionally, previous in vitro data indicates that intimin may have also function in a Tir-independent manner, and we revealed this function using streptomycin pre-treated mice. Lastly, using a toxigenic C. rodentium strain, we assessed the function of pedestal formation mediated by Tir-intimin interaction and found that Tir-mediated actin polymerization promoted mucosal colonization and a systemic Stx-mediated disease that shares several key features with human HUS.DOI
10.13028/amzq-xx16Permanent Link to this Item
http://hdl.handle.net/20.500.14038/31948Rights
Copyright is held by the author, with all rights reserved.Scopus Count
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