| Lactobacillus acidophilus has been thoroughly investigated as a human probiotic; however, there is little evidence to support the notion that L. acidophilus, specifically L. acidophilus NCFM®, will prevent bacterial gastroenteritis. Even though L. acidophilus NCFM® has been thoroughly studied, it is not known if L. acidophilus NCFM ® can transit the gastrointestinal tract successfully or if can prevent illness caused by an enteric pathogen. The objectives of this thesis were to determine if: (1) the delivery vehicles for Lactobacillus acidophilus NCFM® would influence the human fecal microbiota; (2) Lactobacillus acidophilus NCFM ® would protect mice from developing transmissible murine colonic hyperplasia (TMCH) caused by Citrobacter rodentium; and (3) C. rodentium had virulence genes in common with the human foodborne pathogens enterohemorrhagic Escherichia coli O157:H7 (EHEC) and E. coli O39:NM.; There was no apparent collective advantage to using milk versus water as a delivery vehicle for L. acidophilus NCFM® . In addition, continuous feeding of L. acidophilus was required to maintain elevated lactobacilli populations in human subjects. Even though the lactobacilli population did increase while human subjects consumed the probiotic, the exogenous L. acidophilus NCFM ® did not affect the populations other endogenous genera of bacteria.; A mouse model using C. rodentium as a surrogate for EHEC was developed and used to investigate the ability of L. acidophilus NCFM® to prevent gastrointestinal disease. It was determined that L. acidophilus NCFM® did attenuate overt colonic hyperplasia when fed to mice prior to being challenged with C. rodentium. No protective effect was observed when the probiotic was fed to mice at the same time that the pathogen was orally administered.; Furthermore, it was discovered that C. rodentium, EHEC, and E. coli O39:NM are more similar than previously known, these organisms possess multiple virulence genes that are quite similar further validating the use of C. rodentium as a valid model for future probiotic research.; These data indicate that L. acidophilus NCFM ® is efficacious at preventing gastrointestinal illness caused by bacterial pathogens. It appears that it is the frequency of consumption of the probiotic that may influence the efficacy of the probiotic versus the type of delivery vehicle used. |
