Based on the infection, the patient is given a phage preparation that is sensitive to the infection. After consuming this phage medication, the phages travel through the body towards the bacteria they are sensitive towards. Once they reach the bacteria at the site of infection, they attach onto the bacterial cells, and inject their DNA into the cells. This DNA then uses the bacterial cell’s machinery to reproduce very rapidly, making an army of new phages inside the cell.
As the number of phages continues to grow rapidly in the cell, it is no longer able to contain the invading phages. It bursts and the new phages spread to other cells of the same bacterium, looking to reproduce, and thus the cycle continues till there are no more bacterial cells left for the phages to invade. Once all the bacteria are dead, the phages can no longer replicate, and are flushed out from the body.