Date of Award

Winter 1-21-2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Catherine Putonti

Abstract

Enterococcus faecalis is one of the first colonizers of the human gastrointestinal tract, and it plays a role in the intestinal immune development at the very early stages of life. However, it is also an opportunistic pathogen, capable of translocating across the mucosal barrier to cause systemic infections. E. faecalis is also linked to infections including endocarditis, recurrent urinary tract infections (rUTIs), bacteremia, wound infections, meningitis, root canal infections, intra-abdominal and pelvic infections, and septicemia. Persistent enterococcal opportunistic infections have been associated with the production of virulence factors and sharing of antibiotic resistance genes, thus making E. faecalis difficult to kill with current treatments. Bacteriophage, viruses that infect bacteria, are an attractive alternative to antibiotics. In this study, we observed the effects of bacteriophage (phage) infection of E. faecalis in both controlled laboratory conditions and human tissue environments. First, three phage were tested against 22 clinical E. faecalis isolates to determine phage host range. Using transmission electron microscopy (TEM), the phage morphology as well as phage attachment to bacterial cells was determined. Confocal microscopy was used to identify instances where phage DNA insertion into E. faecalis cells suggesting successful absorption. Next, we used confocal microscopy to image interactions between E. faecalis strains and human cells. Using the U2OS cell line, we found that the E. faecalis strains tested were able to attach to the monolayer. When we added fluorescently labeled phage to these wells, we were unable to replicate the bacteria-phage interaction seen when looking at them in isolation. This work was essential in establishing a protocol for imaging attachment and injection of phage DNA into E. faecalis cells and E. faecalis cell attachment to U2OS cells.

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