Food Science and Technology Department


Date of this Version

Spring 4-22-2011


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Food Science & Technology, Under the Supervision of Professor Robert W. Hutkins. Lincoln, Nebraska: April 2011
Copyright 2011 Maria Isabel Quintero V.


For most bacterial pathogens, adherence of the bacterium to the surface of the host cell tissue is a necessary first step for colonization and infection. Agents that inhibit adherence, therefore, could be useful for preventing infections. The goal of this research was to assess the anti-adherent activity of several food-grade prebiotic carbohydrates, plant extracts, and other naturally-derived molecules against enteric pathogens. First, the antiadherent effect of galactooligosaccharides (GOS), polydextrose (PDX), and a GOS-PDX blend was tested against two strains of Cronobacter “Enterobacter” sakazakii. When measured microscopically or by cultural methods, significant reductions in adherence (56% and 71%, respectively) of C. sakazakii were observed in the presence of GOS (16 mg/ml). Adherence inhibition also occurred (48%) when the GOS-PDX blend (8 mg/ml each) was tested, although PDX by itself had less effect. Subsequently, the ability of several prebiotic agents, including chitooligosaccharides (COS) and mannan oligosaccharides derived from yeast cell walls (MOSy) and konjac root (MOSk), to inhibit adherence of enteropathogenic Escherichia coli (EPEC), enterohemorragic Escherichia coli (EHEC) and Salmonella typhimurium to a human HEp-2 cell line was tested. In addition, a high molecular weight component of cranberry (CHMW) was also assessed for anti-adherence. Different fractions of COS significantly reduced adherence of EPEC at a concentration of 16 mg/ml. Although MOSy inhibited EPEC, EHEC, and S. typhumiurim, adherence inhibition was not observed for MOSk. Adherence inhibition of EPEC, EHEC, and S. typhumiurim by CHMW was observed. Finally, the ability of two different types of lactoferrin to inhibit adherence of Cronobacter sakazakii to a HEp-2 human cell line was assessed. Results showed that the adherence of C. sakazakii was significantly reduced at a minimum concentration of 10 mg/ml. However, at higher concentrations (up to 50 mg/ml), further reductions in adherence were not observed. These results show that different prebiotics, plant extracts, and other molecules may be added to foods as a prophylactic treatment to prevent or mitigate infections by enteric pathogens.

Advisor: Robert W. Hutkins

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