The Effect of the T4 Bacteriophage, Sublethal Concentrations of Ciprofloxacin and Metronidazole, and Combined Phage-Antibiotic Use on Escherichia coli B Colony Density

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Money, Austen
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Crohn’s disease is a type of chronic inflammatory bowel disease. The exact cause of the disease is unknown, but recent research suggests a correlation to high levels of pathogenic strains of E. coli in the gastrointestinal tract. These strains are antibiotic-resistant, which creates a need for alternative antibacterial therapies such as phage therapy. Phage therapy is a technique that uses viruses to infect and kill bacteria. The purpose of this experiment was to test the effectiveness of phage therapy in combination with sublethal levels of antibiotics, which has been shown in previous research to improve the antibacterial properties of the phage, against a similar strain of E. coli. The antibiotics used in combination with the phage were metronidazole and ciprofloxacin, the two most effective drugs used to treat patients with Crohn’s disease. It was hypothesized that a combination of ciprofloxacin and a dilution of a phage would result in fewer E. coli colonies in the bacterial lawn of growth. During experimentation, an agar plate was inoculated with a strain of E. coli B, and using a double-layer plaque assay, the bacteriophage and a low concentration of either metronidazole or ciprofloxacin were also added to the plate. This was repeated for the six groups, with a control, a group treated with only the phage, and and one group for each antibiotic treatment not in combination with the phage. It was found that adding metronidazole to the phage significantly improved the antibacterial properties of both treatments, and although the ciprofloxacin/bacteriophage treatment was the most effective, there was not a significant difference between this treatment and the ciprofloxacin treatment.