'Phage therapy' could treat some drug-resistant superbug infections, but comes with unique challenges

As bacteria become resistant to antibiotics, more people will become infected and die of untreatable bacterial infections. By 2050, drug-resistant infections are predicted to kill ten million people a year.

So researchers are desperately seeking viable alternatives. One promising therapy uses specialized viruses called bacteriophages to invade and kill bacteria. They're called "phages" for short.

This "phage therapy" has been used to treat antibiotic-resistant infections in small numbers of people who would have died without another way to kill the bacteria causing their infections.

But phage therapy is complicated, more complicated than prescribing antibiotics and picking up a script from the pharmacy.

What is phage therapy?

In the wake of COVID, we're all familiar with viruses that infect human cells. There are also viruses that infect bacteria, known as phages.

Just as viruses that infect humans only affect certain types of human cells, phages prefer to infect certain types of bacteria. MS2 phage, for example, can infect Escherichia coli (E. coli) and some related bacteria—but not all of them.

Often, phages infect bacteria and just remain there, existing within the bacterium.

Sometimes, phages infect bacteria with lethal consequences for the infected bacterium. This is what can be harnessed and turned into phage therapy.

If the right phage can be found, it can be delivered to the infection site (either intravenously, topically to the skin or by aerosol inhalation), where it will find, infect and kill the bacteria causing the patient's infection.

Since phages don't infect and cause disease in humans, phage therapy selectively targets and kills the bacteria in the patient, and not the patient. An added bonus is phages leave other beneficial bacteria unaffected, unlike antibiotics.

So how is phage therapy prepared?

Before use, the right phage—capable of infecting the bacteria causing the infection—must be matched to target the infecting bacteria. This involves developing comprehensive phage libraries by isolating and selecting phages with the desired properties.

Fortunately, phages are everywhere—in soil, water, plants, animals and us. Finding and characterizing them is straightforward, but takes time.

Successfully matching phage to the specific bacteria causing the patient's infection requires lab technicians to isolate the bacteria first. This takes one to three days.

Then, the isolated bacterium is tested against hundreds of phages from the phage library to find one that can infect and kill that bacterium. The methods are slow, labor-intensive and take another few days.

Finally, when a phage that can kill the bacterium is identified, that specific phage, or a cocktail of multiple lethal phages, must be manufactured and administered to the patient.

Ironically, the unique advantages that make phage therapy a viable treatment for antibiotic-resistant infections bring challenges for treating lots of patients.

This article is republished from The Conversation under a Creative Commons license. Read the original article.