The nice thing about phages is that they also adapt.

'Part of the treatment’s success is due to the “training of the phages,” says Pirnay. This involves directing the evolution of these viruses by growing one generation after the other alongside the bacteria that is infecting the patient. In each generation, the virus that kills the most bacteria is selected and moves to the next round. The result is an elite force of phages specially adapted to fight a specific pathogen...

'“Phages are able to stop the bacteria from being resistant to antibiotics,” she says. “The bacteriophages attack the same molecular targets that bacterias use to avoid the effect of antibiotics. If you administer phages first, then antibiotics, you block their resistance and the infection subsides.”'