Comparing Virulence of Three T4 Bacteriophage Strains on Ampicillin-Resistant and Sensitive E. coli Bacteria

While bacteria have demonstrated antibiotic resistance since the advent of antibiotics, the threat that these resistant microbes pose has recently gained much more attention in scientific and public communities. Antibiotics work by disrupting functions and structures in bacteria that animal cells lack. Bacteria acquire resistance to these drugs through genetic mutations that allow them to sidestep the effects of the antibiotic. When this occurs, antibiotics may not be able to treat an illness caused by resistant bacteria. An alternative therapy is the use of bacteriophages, or viruses that infect bacteria.
In this experiment, we grew cultures of ampicillin-resistant and ampicillin-sensitive K12 strain E. coli and applied three strains of T4 bacteriophage, T4r+, T4r, and T4rIIA, to different cultures of the resistant and sensitive E. coli. After the bacteriophages had time to infect and lyse the bacteria, we determined the lysed percentage of each culture.
The results of this work showed that the wild type T4r+ caused the greatest amount of lysis of E. coli. There was not a significant difference in percentage lysed between cultures containing resistant and sensitive E. coli infected with the same strain of bacteriophage. These results suggest that the T4r+ bacteriophage may be the most effective in treating an E. coli infection, regardless of the ampicillin resistance of the E. coli.