Widespread use of antibiotics in medicine and agriculture has led to the emergence of antibiotic,

or multi-drug, resistant bacterial pathogens (1–7). This indiscriminate use of antibiotics and the slowing discovery of new antibiotics has caused the number of multi-drug resistant pathogens to increase at a rapid rate. Thus, researchers have turned to other methods of treatment, one being treatment with bacteriophages (3, 8–10). Unfortunately, while phages act as effective bactericides, bacteria can readily evolve resistance to phage infection (1, 3, 11). When Escherichia coli are infected with a phage that binds to lipopolysaccharides, LPS, phage resistant mutant arise that show a reduction in resistance of antibiotics that use lipid mediate entry; such genetic trade-offs could be clinically relevant (11). We evaluated whether a similar genetic trade- off between phage resistance and antibiotic susceptibility was achieved in Pseudomonas aeruginosa following infection with PB-1, a phage known to bind to LPS. Additionally, we evaluated how phage resistance and antibiotic susceptibility change after co-culture with a secondary phage, PP7. While phage treatment did not induce significant changes in antibiotic resistance, we did observe phenotypic changes in P. aeruginosa. Bacteria treated with PB-1, PP7 or both phages showed disruption and delay in biofilm formation and secretion of pigmented molecules. Further research is necessary to determine if phage infection causes biofilm disruption in a clinically relevant manner.


Strand, Stephanie


Biochemistry and Molecular Biology


Biochemistry | Microbiology | Molecular Biology | Pathogenic Microbiology

Publication Date


Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis



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