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

5-24-2009

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Scott Hultgren

Abstract

Urinary tract infections: UTIs) affect 13 million women annually in the United States and are predominately caused by uropathogenic Escherichia coli: UPEC). In a murine cystitis model, UPEC utilize a multistep pathogenic pathway in which they invade and form intracellular bacterial communities: IBCs) within bladder facet cells. Type 1 pili expressing the adhesin, FimH, are necessary for UPEC binding and invasion of urothelial cells and formation of IBCs. UPEC ultimately disperse from the IBC, many with filamentous morphology, and infect other host urothelial cells. Using a panel of UPEC clinical isolates, this work evaluates the conservation of the IBC pathway across UPEC, the function of a UPEC pathogenicity island: PAI) in the UPEC pathway, and the therapeutic effect of inhibition of FimH. Investigation of 18 clinical isolates revealed that the majority of isolates proceed through the IBC cascade confirming its relevance in UPEC infection. Due to the commonality of the UPEC pathway, this panel of clinical isolates was used to investigate other determinants important in UPEC infection. One potential virulence determinant is pUTI89, isolated from UTI89. pUTI89 has many characteristics of a PAI thus it was evaluated for its presence in UPEC isolates and its role in pathogenesis. Evidence of pUTI89 was found in 67% of UPEC isolates tested. Studies revealed that while there was no observable phenotype in vitro in the absence of pUTI89, there was a significant defect in binding, invasion and colonization at early time points post-infection, however, infection levels were restored by 24h post-infection. Since pUTI89 is not essential to UPEC infection, type 1 pili were used to develop a therapeutic against UPEC infection. Binding and invasion are critical to the UPEC pathway, thus inhibition of these early steps could result in unsuccessful colonization of the bladder. Knowledge of the FimH mannose-binding pocket enabled the rational development of mannosides that competitively inhibit binding to mannosylated uroplakins on the bladder surface. These studies demonstrated the commonality of the IBC pathway among UPEC isolates as well as the importance of pUTI89 in early stages of UPEC infection. Knowledge of the UPEC pathway facilitated the development of novel therapeutics to inhibit binding and invasion and reduce infection.

Comments

Permanent URL: http://dx.doi.org/10.7936/K77W6962

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