Food Science and Technology Department


Date of this Version

Summer 7-2014


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 & Technology, Under the Supervision of Professor Robert W. Hutkins. Lincoln, Nebraska: July, 2014

Copyright (c) 2014 Maria Isabel Quintero-Villegas


Bacterial adherence is the first and one of the most important steps in bacterial pathogenesis. Adherence to host cell surfaces requires that the bacteria recognize specific receptors in the surface of epithelial cells. Therefore, agents that act as molecular decoys to interfere with adherence could be useful prophylactic treatments to prevent or mitigate the onset of infections. The goal of this research was to assess the ability of several food grade non-digestible oligosaccharides (NDOs) to act as molecular decoys and prevent bacterial adherence in vitro as well as in vivo. First, the antiadherence effect of specific species chitooligosaccharides (CHOS) at different concentrations were tested against enteropathogenic Escherichia coli (EPEC). Microscopic evaluation indicated that CHOS reduce adherence of EPEC to HEp-2 cells by more than 90%. Subsequently, the antiadherence activity of lactoferrin, alone and in combination with a 1:1 mix of galactooligosaccharides (GOS) and polydextrose (PDX), was tested against Cronobacter sakazakii. Adherence was assessed by quantitative PCR (qPCR) and results indicate that lactoferrin inhibits adherence of C. sakazakii to HEp-2 cells at a minimum concentration of 10mg/ml. Lactoferrin combined with the GOS:PDX mix did not further inhibit adherence, suggesting there is not an additive effect between lactoferrin and GOS:PDX. Moreover, the ability of GOS to reduced adherence was assessed in vivo in a Citrobacter rodentium mouse model of infection. Conventional and germ free C57Bl/6 mice were supplemented with GOS in the drinking water to receive a dose of 5000mg of GOS/kg of body weight (daily), for two weeks prior to infection and during the course of infection (10 days). At necropsy, adherence and disease severity were assessed in the distal colon. Results indicated that GOS reduces adherence of GOS in conventional mice but not in germ free mice. Nevertheless, the lesions were not improved in mice supplemented with GOS as compared to the control. Finally, the antiadherence effect of yeast derived mannan oligosaccharides (MOSy) was tested against Vibrio cholerae. Adherence inhibition was observed at a minimum concentration of 2mg/ml and reached its maximum at 8mg/ml. These results show that different NDOs may be used as a prophylactic treatment to prevent adherence, hence preventing or mitigating infections by enteric pathogens.

Advisor: Robert W. Hutkins