Big fleas have little fleas,
Upon their backs to bite ’em,
And little fleas have lesser fleas,
and so, ad infinitum

Bacteria are everywhere, but it’s not always an easy life. Just as all creatures have tormentors, out gut bacteria have viruses that can kill them in a most gruesome way: they sneak into the bacteria and force the poor microbe to produce hundreds of copies of themselves. Finally the viruses are too numerous to fit. They explode out of the bacteria’s body and spread out to infect more bacteria. These special viruses are called phages, which means “eaters”.

Each phage is very particular about which kinds of bacteria they will attack. Unlike broad-brush antibiotics, they home in on a single species and leave other bacteria alone. They are pretty easy to target: you just smear the bacteria you want to kill on a petri dish and let them grow to form a film. Then you place spots of various phages on top. When a clear spot shows up in the dish, that means a phage has obliterated the target bacteria. Just cut out that spot and you have a few million phages, ready to go. Unlike antibiotics that may require multiple rounds to do the job, phages keep multiplying as long as their target exists.

Surprisingly, phages have been known and used for decades — in Eastern Europe. Only recently has the FDA shown an interest. But there are some great anecdotes that are making the FDA sit up and take notice. With antibiotic resistance and all the other problems that come with antibiotics, it’s about time. Phages could represent the medicine of the future.