Publication Date

2006

Document Type

Thesis

Committee Members

Oleg Paliy (Advisor)

Degree Name

Master of Science (MS)

Abstract

Escherichia coli (E. coli) is a gram negative bacterium commonly found as a commensal in the intestinal tract of humans and other warm blooded animals. The commensal strains of E. coli are non-pathogenic and do not cause an infection in the host. However, some strains of E. coli are pathogenic and can cause several diseases in humans that include neonatal meningitis, intestinal infections and urinary tract infections. Almost 80-85% of the uncomplicated urinary tract infections are caused by uropathogenic E. coli. Our project involved the characterization of 12 strains of E. coli, isolated from humans in health and disease. These strains were characterized since no studies had been conducted on them previously. The E. coli strains were isolated from patients with urinary tract infections and from the intestinal tracts of partners of these patients. Laboratory E. coli strain K12 served as a control. Phenotypic studies were carried out by studying the bacterial physiology in three different conditions. Motility tests were done to identify phenotypes that were similar to and different in behavior with respect to the wild type. Since antimicrobial resistance was a growing problem in urinary tract infections, susceptibility tests were done for these novel strains of E. coli, with the most commonly used antibiotics to treat these infections. Additionally phenotypic profiles were generated for the wild type strain as well as one uropathogenic strain using Phenotype Microarrays manufactured by Biolog., Inc which was a novel technique especially for uropathogenic strains. These plates were unique in helping us identify different phenotypes within a limited time period. The results of our tests showed, some isolates whose phenotypic behavior differed, in terms of growth and motility when compared to the wild type. Antibiotic susceptibility tests enhanced our understanding of determinants of resistance which was crucial for the management of urinary tract infections. Phenotype micro array profiles generated for 2 strains, the wild type E. coli strain and one uropathogenic strain showed a total of 37 differences in carbon, nitrogen, sulfur and phosphorus metabolism in these strains. These differences indicated the likely genome variations between two strains, a fact that was shown for recently sequenced UTI strain CFT073. Therefore phenotypic characterization was useful in establishing genetic variability of the isolates and more specifically of E. coli strains causing urinary tract infections.

Page Count

79

Department or Program

Microbiology and Immunology

Year Degree Awarded

2006

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