'Phago' is a term used as a prefix in Latin meaning ‘Eating’ or ‘swallowing’.
Phago ultimately comes from the Greek phageîn, which means “to eat, devour.”
The term phagocytosis means cell eating. It is a process that is a part of the immune response by macrophages that involves eating of the cellular debris that remain after the white blood cells have destroyed the antigen or invading pathogen.
The virus which infects and destroys bacteria is also called a bacteriophage.
For medical applications, they are very specific so can infect and destroy bacteria without harming the surrounding human cells.