Author ORCID Identifier

0009-0006-6372-9722

Document Type

Thesis

Date of Award

Spring 4-29-2026

Keywords

Microbiology, biofilms, recurrent urinary tract infection, urinary tract infection, antibiotic resistance, Enterococcus faecalis, Escherichia coli

Degree Name

Biochemistry (BS)

Department

BIOCHEMISTRY

First Advisor

Dr. Claudia N. H. Marques

Second Advisor

Dr. Gretchen J. Mahler

Third Advisor

Dr. Caitlin J. Light

Abstract

Urinary tract infection (UTI) is a major women’s health issue, affecting approximately 40% of women during their lifetime. Formation of a biofilm by UTI-causing bacteria poses a major challenge in treatment, as the protection provided by the biofilm hinders both host defenses and antibiotic treatment. Failure to eradicate these infections causes them to become recurrent (rUTI). Previous research indicates that rUTI may be comorbid with a mutation in the SERPINE1 gene, which causes fibrin to accumulate within the body. Literature also indicates that fibrin provides a better scaffold for bacterial attachment and, subsequently, biofilm formation. In this work it was hypothesized that fibrin accumulation in rUTI patients, resulting from a mutation in the SERPINE1 gene, contribute to the resilience of bacteria to antimicrobial treatment. To test this in vitro, a 3D model was constructed around a fibrin hydrogel. To analyze the effect of fibrin on biofilm growth and response to treatment, single species biofilms of E. faecalis and E. coli were cultured in the presence and absence of fibrin, exposed to the antibiotic ciprofloxacin, and allowed to recover from treatment. Bacterial viability and relative gene expression were quantified throughout the experiment. Gene expression was assessed for virulence factors related to attachment, nutrient acquisition, and evasion of host defenses using RT-qPCR. To assess host cell outcomes in co-culture with single-species biofilms in the absence and presence of fibrin, the conditions were replicated with the addition of human bladder epithelial cells. Results showed that in the presence of fibrin, bacterial numbers are increased; but conversely, the presence of fibrin may hinder biofilm recovery from treatment. Mammalian cell viability was higher in the absence of fibrin, suggesting lower bacterial numbers and minimized host damage. Virulence gene expression exhibited differences between samples cultured on fibrin and polystyrene, indicating that fibrin alters biofilm behavior. Expression of virulence genes was also influenced by stage of treatment, suggesting biofilm responses to antibiotic treatment. Further research may investigate the effect of fibrin on dual-species growth, the transcriptional profile of single-species in co-culture with mammalian cells, and the efficacy of different treatments/combination therapies.

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