Date of Award


Degree Type


Degree Name

Master of Science (MS)


Microbiology and Immunology


Clostridium difficile infection (CDI), caused by the anaerobic spore-former C. difficile, is a major cause of health-care associated morbidity. CDI occurs in individuals that have a disrupted GI tract microbiota, typically in patients who are on antibiotic therapy. After recovery from an episode of CDI, approximately, 15-30% of patients experience relapse of disease. The mechanism of relapse is not well understood. It is plausible for relapse to occur if C. difficile cells and spores associate with the GI tract mucosa during infection and persist after infection. However, little is known about the association of cells and spores with the GI tract mucosa during and after infection. To address this gap in knowledge, I visualized C. difficile vegetative cells by performing fluorescence in situ hybridization, using a 16S rRNA probe, and C. difficile spores by performing immunofluorescence microscopy, using anti-HMW SlpA antibodies, in the mouse cecum and colon both during (2-10 days post-infection) and after infection (15-40 days post-infection). C. difficile cells and spores were present in the outer mucus layer and rarely associated with the inner mucus layer or the epithelium during and after infection in the cecum and colon. I also determined whether the C. difficile cell surface layer protein A (SlpA), which is associated with the C. difficile spore surface, mediates spore adhesion to mucin in vitro. Even though the results of our assay did not indicate an interaction between SlpA on the surface of spores and mucin, other approaches could be successful in measuring this interaction. Collectively, the results from this study suggest that association of C. difficile vegetative cells and spores with the outer mucus layer during infection might be an important step in colonization. We suggest that after infection, the association of vegetative cells and spores with the outer mucus layer might be important in relapse of disease.

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