Question: Why do bacteriophages target bacteria, not human cells and do not affect human cells? Could phages ever target human cells instead of bacteria? How long will it take for bacteriophages to be used to combat the rising strains of bacteria which have developed resistance to antibiotics, e.g. in hospitals?

Lucy Kelly answered on 14 Mar 2020:

Wow, really thorough question!
Phages target bacteria and not human cells because they bind to proteins called ‘receptors’ only on bacterial cells. So even if they come into contact with human cells, they can’t bind to them – they wouldn’t be able to target human cells instead of bacteira.
Phages have already been used in some cases of antibiotic resistant bacteria! They’re only used when we have run out of antibiotic options to treat patients and the patient is really really sick. Phages have also been used for decades in countries like Russia and Georgia, we’re only just beginning to catch up! I think it will be a few years before they’re used commonly here though, we need to do a lot more safety testing first.