GSBS Dissertations and Theses
Publication Date
2012-03-28
Document Type
Doctoral Dissertation
Academic Program
Molecular Genetics and Microbiology
Department
Molecular Genetics and Microbiology
First Thesis Advisor
John M. Leong M.D., Ph.D.
Keywords
Enterohemorrhagic Escherichia coli, Escherichia coli Infections, Hemolytic-Uremic Syndrome, Shiga-Toxigenic Escherichia coli, Shiga Toxin, Citrobacter rodentium, Adhesins, Bacterial, Escherichia coli Proteins
Abstract
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.
Repository Citation
Mallick EM. (2012). A New Murine Model For Enterohemorrhagic Escherichia coli Infection Reveals That Actin Pedestal Formation Facilitates Mucosal Colonization and Lethal Disease: A Dissertation. GSBS Dissertations and Theses. https://doi.org/10.13028/amzq-xx16. Retrieved from https://escholarship.umassmed.edu/gsbs_diss/601
DOI
10.13028/amzq-xx16
DOI Link
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Amino Acids, Peptides, and Proteins Commons, Animal Experimentation and Research Commons, Bacteria Commons, Bacterial Infections and Mycoses Commons, Biological Factors Commons, Enzymes and Coenzymes Commons, Female Urogenital Diseases and Pregnancy Complications Commons, Hemic and Lymphatic Diseases Commons, Immunology and Infectious Disease Commons, Male Urogenital Diseases Commons