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Phage Comeback

Phage Comeback

Overprescription and misuse of antibiotics has fueled the rise of antibiotic-resistant bacteria. That's why researchers are looking to the past for future alternatives. You'll hear about one possibility in this Science Update.


Transcript

New life for an old medical treatment. I'm Bob Hirshon and this is Science Update.

For more than half a century, antibiotics have been the standard treatment for many bacterial infections. But before antibiotics came on the scene, doctors often used specialized viruses called phages to kill disease-causing bacteria.

According to Carl Merril, Chief of Biochemical Genetics at the National Institutes of Health, phage therapies fell out of favor because the organisms weren't well understood.

Merril:

They really didn't understand the basic biology of these viruses. And their strengths and their weaknesses. And so in fact they were not used in the best proper manner.

But now, Merril says phages are making a comeback. Modern technology could make it easier to purify them and to quickly identify the best one to use, which were major hurdles in the past. Phages could even be genetically engineered to attack a wider range of bacteria.

Merril:

One of the main reasons people are interested in phage now is that the problem with antibiotic resistance is becoming ever more important. I mean there are almost an infinite variety of phage. And so there's a lot of opportunity here.

The task now is to test phages thoroughly to ensure they're both safe and effective over the long run. For the American Association for the Advancement of Science, I'm Bob Hirshon.


Making Sense of the Research

Got an infection? Why not fight it with a virus that actually kills the bacteria? We know how good viruses are at making people sick. Against a simple foe like bacteria, one would expect them to be even more powerful.

If it sounds like an effective strategy, you're right. In fact, a study in the late 1980's suggested that phage were actually more effective than several different antibiotics in fighting disease in animals. It's no wonder that when phage were discovered in the early 20th century, they looked like a miracle cure. And in fact, they became widely used around the world.

But soon, some practical limitations became obvious. One problem is that phage are incredibly specific. For example, a particular kind of phage typically attacks only one strain of a particular kind of bacteria. So if you get strep throat from Streptococcus bacteria, you need a phage that attacks whatever strain of Streptococcus that's infecting you.

Since viruses can have dozens or even hundreds of different strains, that's a complicated question to answer. And early in the 20th century, it just wasn't possible to run a test quickly enough to figure out which strain of phage to use. In fact, scientists weren't even fully aware of the specificity problem at the time—but it did get in the way of effective treatments.

Another problem with phage is that you have to grow them in cultures of the same harmful bacteria that they're meant to fight. Which leads to a problem when you need to put the phage in the patient. How do you strain out the bad stuff and leave the phage behind? Early techniques were often successful in filtering out the bacteria, but not the toxins that the bacteria had made in the culture. And the results could be deadly.

Today, there are advanced techniques that can identify and purify phage more efficiently. For example, scientists can insert something called a "reporter gene" into a culture of phage, which makes the phage give off light if it successfully attacks the target bacteria. This makes it easier to pick out the right strain of phage to use. And modern techniques like chromatography—a sophisticated way of separating the components of a mixture—make it possible to isolate the phage from any undesirable residues.

As Merril notes, phage are of particular interest to scientists now because many antibiotics are becoming ineffective. Bacteria are evolving into strains that are resistant to the drugs we've been dousing them with for fifty years. New antibiotics will undoubtedly breed new resistance, so it's critical that we develop as many different ways to fight bacteria as we can.

Interestingly, an important ally in the advancement of phage technology is Russia. Back in the Cold War days, the former Soviet Union was scientifically isolated from the West, and had little access to antibiotics. Instead, phage were cultivated as the treatment of choice for decades after they fell from Western favor. By working with scientists from the former Soviet Union, today's researchers can catch up on all the advances they achieved.

Now try and answer these questions:

  1. What are phage?
  2. What are the advantages and disadvantages of using phage to fight infections?
  3. Why are phage being re-considered after so many years of obscurity?
  4. Do you think the fight against antibiotic resistance should focus on new technology, or more judicious use of antibiotics? Give reasons for your answer.

For Educators

Cells Alive has an overview of bacteriophage, including a time-lapse movie of phage infecting E. Coli bacteria.

In Bugs Fighting Back in Evolutionary War on Humans?, from National Geographic, read about the rapid evolutionary changes that are creating drug-resistant pathogens and insecticide- and herbicide-resistant insects and weeds.

Antibacterial Household Products, a paper presented at the 2000 Emerging Infectious Diseases Conference in Atlanta, describes the possible impact of common household cleaners on the evolution of drug-resistant bacteria.


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