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.

The sentinel lymph node biopsy is part of recommended surgical staging guidelines in patients with early stages of cervical cancer. High success rates of bilateral detection of SLN are achieved in sites with adequate experience with this procedure. The sentinel lymph node biopsy without systematic pelvic lymph node dissection is currently considered inadequate procedure for stages IB to IIA of the disease. One of the benefits of sentinel lymph node detection is extensive histopathological examination using the ultrastaging protocol enabling detection of small metastases (i.e. micrometastases). At the moment, there is lack of evidence about oncological safety of sentinel lymph node biopsy which might replace systematic lymph node dissection in the future. Prognostic significance of micrometastases is also controversial due to the lack of data about their potential presence in non-sentinel lymph nodes in cases with negative sentinel lymph nodes. This dissertation deals with the concept of sentinel lymph node biopsy in the cervical cancer and focuses on several topics. We have shown that the presence of micrometastasis is associated with significant negative impact on patients' prognosis on the largest retrospective cohort of patients ever published. Only 67% of patients with micrometastasis have...