Date of Award

Spring 5-15-2015

Author's School

Graduate School of Arts and Sciences

Author's Department

Biology & Biomedical Sciences (Molecular Microbiology & Microbial Pathogenesis)

Degree Name

Doctor of Philosophy (PhD)

Degree Type

Dissertation

Abstract

Urinary tract infections (UTIs) are among the most common bacterial infections worldwide, costing greater than $2 billion in healthcare costs and lost wages yearly in America alone. The lifetime risk for a woman exceeds 50% with 25-40% of these suffering recurrent infections. Two of the most important risk factors for recurrent UTI are prior UTIs and sexual intercourse. Over 80% of UTIs are caused by uropathogenic Escherichia coli (UPEC), which binds and invades superficial facet cells lining the bladder surface. UPEC expresses extracellular fibers called type 1 pili with a terminal mannose-binding adhesin, FimH, which interacts with mannosylated uroplakin residues on the urothelium. UPEC replicates in the cytoplasm of bladder cells into biofilm-like intracellular bacterial communities (IBCs) in a protected niche. In C3H/HeN mice, a robust, systemic, immune response at 24 hours precedes the development of persistent bacteriuria and chronic cystitis, which lasts indefinitely. A less robust immune response results in resolution of the infection.

I determined the population dynamics during UPEC infection with a set of 40 variants of a clinical isolate, UTI89, each with a unique genetic sequence detectable by multiplex PCR. I identified a significant population bottleneck during the first 24 hours coinciding with the inflammatory response. Furthermore, I tested a panel of FimH alleles under positive selection and found several that impacted the ability of UPEC strains to form IBCs and promote chronic cystitis. These pathoadaptive alleles govern the ability of FimH to bind mannose by dynamically interconverting between a compact, low-affinity conformation and an elongated, high-affinity state. This dynamic equilibrium is crucial for virulence as alleles locked in either conformation are attenuated. I also developed a model of frequent inoculation of UPEC into the urinary tract to investigate the clinical link between frequent sexual intercourse and UTI risk. By inoculating mice twice during acute infection, I found a dramatic increase in the proportion of mice that experienced chronic cystitis. Taken together, this thesis defines bacterial and behavioral factors that increase the risk for chronic and recurrent UTI, providing rationale for the development of novel therapeutics targeting bacterial invasion to limit infection by excluding UPEC from intracellular niches.

Language

English (en)

Chair and Committee

Scott J Hultgren

Committee Members

John Atkinson, Daniel Goldberg, David Hunstad, Amanda Lewis, Mark Miller

Comments

Permanent URL: https://doi.org/10.7936/K7B27SGG

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