Theses and Dissertations from DePaul University

Date of Award

Spring 2026

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Science

College

College of Science and Health

First Advisor

Joanna Brooke

Abstract

Stenotrophomonas maltophilia is a multidrug-resistant Gram-negative pathogen that can cause severe respiratory tract, urinary tract, and bloodstream infections in susceptible patients (Brooke, 2021). Its ability to form biofilms is a large contributor to its antibiotic resistance and virulence (Brooke, 2021). Due to a rise in antibiotic resistance, new treatment strategies against bacterial infections are being developed. Bacteriophages, or phages, are an alternative to antibiotics. They are viruses that infect and kill bacteria, and they have been used to treat life threatening infections (Aslam et al., 2020). Sometimes, phages and antibiotics can work synergistically to treat infections (Gu Liu et al., 2020).   This thesis focuses on bacteriophage Bfi2 (Biofilm formation inhibitor 2), a novel virus infecting S. maltophilia. Bfi2 is a virulent phage that forms plaques on the lawns of S. maltophilia K279a. Bfi2 has demonstrated the ability to reduce the planktonic cells associated with both new and mature S. maltophilia biofilms. In this study, it was demonstrated that Bfi2 can also inhibit regrowth of mature biofilms. When Bfi2 was combined with two antibiotics used to treat S. maltophilia infections, ciprofloxacin and levofloxacin, no synergistic effects were seen against mature S. maltophilia biofilms. Because Bfi2 can inhibit further growth of S. maltophilia biofilm cells, this phage demonstrates a potential for use in phage therapy. However, more research to characterize this phage will need to be done.

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Available for download on Thursday, July 29, 2027

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