Food Science and Technology Department


Date of this Version

November 2006


A DISSERTATION Presented To the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy
Major: Food Science and Technology
Under the Supervision of Professor Robert W. Hutkins
Lincoln, Nebraska
November, 2006
Copyright 2006 Kari Shoaf.


Antiadhesion therapy has been found to be a very promising means to prevent and treat infections in the respiratory, urinary, and gastrointestinal tract. Despite the considerable research interest in antiadhesives, relatively little is known about the ability of commercial dietary oligosaccharides, such as prebiotics, to inhibit pathogen adherence. The goal of this research was to determine if commercially available prebiotic oligosaccharides could function as antiadhesive agents against enteropathogenic E. coli (EPEC).

To investigate the ability of prebiotics to inhibit EPEC adherence, inhibition assays were performed by comparing adherence rates of EPEC on HEp-2 and Caco-2 cells in the presence of galactooligosaccharides (GOS), inulin, fructooligosaccharides, lactulose, or raffinose. These data showed that GOS significantly reduced binding of EPEC more than the other prebiotics tested. In addition, binding inhibition by GOS was shown to be dose-dependent and saturable at 16 mg/ml. Microscopic analyses indicated that GOS also reduced the number of EPEC per microcolony and the total number of microcolonies per infected cell.

Both therapeutic and prophylactic GOS treatments were also examined. GOS was unable to displace previously adhered EPEC, but could prevent EPEC adherence when administered prior to infection. Additionally, GOS did not affect EPEC autoaggregation. To determine if GOS was inhibiting adherence at a molecular level, the expression of BfpA, a bundle forming pili protein involved in localized adherence, was examined. GOS did not affect BfpA expression indicating that adherence inhibition was not due to the absence of this adhesin.

To further examine the role of EPEC adhesins in GOS-mediated adherence inhibition, adherence assays using HEp-2 and Caco-2 cell lines were performed using isogenic EPEC mutants. In general, GOS did not affect the adherence of strains lacking BfpA, suggesting that GOS may interfere specifically with BfpAreceptor interactions rather than with other potential EPEC adhesins and their receptors. These results show that commercial prebiotics, particularly GOS, directly inhibit the adherence of E. coli, and provides evidence that these agents may be used as antiadhesives against pathogens in both humans and animals.
Advisor: Robert W. Hutkins

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