Investigation of the Synergistic Effects of Bacteriophage λ and Antibiotics on Escherichia coli HT115

Phage therapy is an emerging strategy that uses bacteriophages to selectively kill bacteria. This thesis aims to investigate the combinatorial effects of phages and antibiotics in their ability to induce synergistic bacterial lysis and to assess whether phages can reduce bacterial resistance to specific antibiotics. The study focused on the bacterial strain Escherichia coli HT115, which is resistant to ampicillin and sensitive to tetracycline. Different concentrations of these antibiotics were tested in combination with high and low concentrations of the bacteriophage λ. Preliminary procedures included assessing the susceptibility of the bacterial strain to these antibiotics by antibiogram analysis and to phages by plaque assays. To define the optimal phage concentrations used in the experiments, the multiplicity of infection (MOI) was calculated through the determination of CFU/mL and PFU/mL. The effects of the treatments on the bacterial growth were monitored in real time over 18 hours using a microplate reader through optical density measurements at 600 nm (OD600).