Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Biology and Biomedical Sciences: Molecular Microbiology and Microbial Pathogenesis

Language

English (en)

Date of Award

1-1-2012

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Scott Hultgren

Abstract

Nosocomial urinary tract infections: UTIs) are a very common result of catheterization with 3 to 7% risk of developing catheter-associated UTIs: CAUTIs) each day catheterized. As multi-drug resistance increases in uropathogens, it is imperative to better understand the effects of catheterization on the urinary tract and pathogenesis. Further, microbial colonization and biofilm production on the surface of urinary catheters are a common component of CAUTIs. Thus, this dissertation focuses on understanding the contribution of known biofilm determinants to urovirulence of Enterococcus faecalis: a common nosocomial uropathogen) and uropathogenic Escherichia coli: UPEC): the most common causative agent of UTI), and the effects of catheterization on bladder physiology using in vitro and optimized in vivo models. In vitro studies reported here demonstrated that E. faecalis produces DNA-dependent biofilms, which require both SrtA and Atn for efficient attachment as well as extracellular DNA from autolytic processes during the accumulative phase for maturation and architectural stability of the biofilm under both static and hydronamic conditions. Further, in vivo studies optimizing and using a rodent model of foreign body-associated UTI to mimic conditions of indwelling urinary catheters in humans underscored the importance of biofilm formation, although in vivo required only a subset of the identified in vitro biofilm-promoting factors such as sortases, for the establishment of persistent enterococcal UTIs despite the acute inflammatory response ensuing from urinary implantation. This response was characterized in these studies and shown to involve bladder wall edema, partial disruption of the epithelial layer, vascular permeability, production of pro-inflammatory cytokines, and recruitment of myeloid cells, particularly neutrophils. During infection of implanted murine bladders, it was shown that type 1 pili mediate UPEC adherence and invasion, similar to what was observed in non-catheterized bladders. Studies in this murine model further demonstrated that microbial reservoirs established during previous UPEC infection could serve as a nidus for urinary catheter colonization upon subsequent implantation. Specific targeting of type 1 pili with small molecule inhibitors of the pilus tip adhesin, FimH, in combination with trimethoprim/sulfamethoxazole prevented UPEC CAUTI. This finding establishes a proof-of-principle for the development of novel therapies to prevent and eventually treat UPEC CAUTI in the face of the rise of antibiotic resistant uropathogens. Overall, the optimization and use of the murine model of foreign body-associated UTI represents a significant advance in the understanding of the pathophysiology of E. faecalis and UPEC uropathogenesis in CAUTIs and is a valuable tool for the identification of virulence factors, including enterococcal sortases and UPEC type 1 pili, involved in these infections. Further research is required to uncover other biofilm and virulence determinants specifically required for UTIs as well as host factors that can serve as potential antimicrobial targets and biomarkers for the prevention, diagnosis, and treatment of enterococcal and UPEC CAUTIs.

Comments

Permanent URL: http://dx.doi.org/10.7936/K78W3BBF

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