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Antibiotic Resistance, Bacteriophages, and Phage Therapy

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

A bacteriophage, or phage, is a virus that attacks bacteria.

A bacteriophage, or phage, is a virus that attacks bacteria.

Antibiotic Resistance: A Serious Problem

The discovery of antibiotics and their ability to kill bacteria was an exciting development in human history. For a while, antibiotics were a wonder cure for bacterial infections. They saved a multitude of lives and relieved misery and discomfort. Antibiotics are still useful today, but an increasing number of bacteria are becoming resistant to the effects of the drugs.

Antibiotic resistance is a very serious problem. New antibiotics or new methods to fight bacteria are needed in order to treat the infections that threaten our lives and our health. Phage therapy—the use of specific viruses to fight dangerous bacteria—might be one solution for this dilemma.

A demonstration of antibiotic resistance in bacteria

A demonstration of antibiotic resistance in bacteria

The dishes above contain bacteria. Bacteria in the left dish have been killed by antibiotics released by the small white disks, as shown by the clear areas in the murky background. The bacteria in the dish on the right are resistant to some of the antibiotics, as shown by the lack of clear spaces around some of the disks.

How Does Antibiotic Resistance Develop?

DNA and Genes

The genes of a bacterium or a human are part of a long molecule known as DNA, or deoxyribonucleic acid. Genes give bacteria and humans their characteristics because they contain the code for making proteins, which are used in multiple ways. Although the basic structure of the genes in a DNA molecule is the same, the sequence of chemicals called nitrogenous bases in each gene is different. This variation allows a gene to code for a specific protein.

Genetic Differences

The members of one species of bacteria are similar to each other genetically, but they aren't identical. Bacteria pass DNA to other bacteria during a process called conjugation. They also develop new characteristics due to mutations, which are changes in the structure of a gene caused by factors such as radiation and certain chemicals. In addition, errors made when DNA replicates just before cell division result in genetic changes.


When a suitable antibiotic is used to treat a population of bacteria, most of the bacteria die, leaving room in the habitat for other organisms. A few of the bacteria may have a pre-existing gene variant or group of genes that gives them resistance to the antibiotic. The resistant individuals survive and reproduce, thereby spreading their beneficial genes through the growing population. Bacteria reproduce rapidly—some as often as every twenty minutes—so a resistant bacterial population can appear quickly.

This is a colorized view of MRSA cells, or Methicillin-resistant Staphylococcus aureus. Methicillin is an antibiotic.

This is a colorized view of MRSA cells, or Methicillin-resistant Staphylococcus aureus. Methicillin is an antibiotic.

The main driving driving factors behind antibiotic resistance are the overuse and misuse of antibiotics.

— CDC (Centers for Disease Control and Prevention)

Use of Antibiotics

Antibiotics have been widely used around the world for both major and minor infections. They are sometimes prescribed in situations where they're not needed, such as in the treatment of viral infections. Antibiotics don't destroy viruses. The excessive use of antibiotics can increase the population of resistant bacteria.

It's a scary thought, but even mainstream health organizations are saying that there may soon be diseases that are untreatable, just as they were before the discovery of antibiotics. Some illnesses are taking longer to cure than in the past. Doctors could once choose from several different antibiotics to treat a disease; in some cases only one now works.

Despite the problems associated with antibiotics, if a doctor tells a patient that an antibiotic is required to treat their health problem, they should take it. They should also make sure that they follow all of the instructions accompanying the prescription and ask the doctor or pharmacist any questions that they would like answered.

Scientists are investigating the use of bacteriophages to fight disease. This may become important in the future. Viruses have a relatively simple structure compared to the cells of bacteria and other organisms and are sometimes considered to be nonliving. When they enter a cell they control it in exquisite detail, however. Bacteriophages are a distinct category of viruses.

A phage injecting its genome (a piece of DNA or RNA) into a bacterial cell.

A phage injecting its genome (a piece of DNA or RNA) into a bacterial cell.

The Lytic Cycle of a Bacteriophage

A bacteriophage, or phage, is a virus that attacks bacteria. During the attack, the phage sends its genetic information into a bacterial cell and "forces" the cell to make new virus particles. The virus particles are released as the bacterial cell bursts and can then infect new cells. The phage infection kills the bacterium.

Many phages have an interesting shape that reminds some people of a lunar lander. A phage is made of a protein coat surrounding a molecule of DNA or a similar chemical known as RNA (ribonucleic acid).

Phages infect bacteria in a process called the lytic cycle. The word "lytic" comes from the noun "lysis", which means splitting of a cell. The basic steps in the lytic cycle are as follows.

  1. A phage attaches to the membrane of a bacterial cell with its "tail".
  2. The phage then injects its DNA into the bacterial cell.
  3. The viral DNA takes over the cell's mechanisms for making DNA and protein so that new virus particles can be assembled.
  4. The new virus particles (or phages) burst out of the cell.
  5. Each virus particle then infects a new bacterial cell.

Some scientists consider viruses to be nonliving, since they aren't made of cells and they can't reproduce on their own. In addition, they can remain completely inactive for long periods of time. Nevertheless, their behavior as they attack and control a bacterium is amazing. Bacteriophages and other viruses seem to exist on the border between a collection of inanimate chemicals and life.

A Phage Attacks a Bacterial Cell

What Is Phage Therapy?

Each type of phage attacks a specific strain of bacteria, but it doesn't attack human cells or other types of bacteria. Therefore, bacteriophages could be used as therapeutic agents inside our bodies. This process is actually happening in countries that were once part of the Soviet Union and is known as phage therapy. The therapy has been used for many years in some parts of the world, with apparent success. Now western scientists are studying the effectiveness and safety of phage therapy.

Phage therapy is very interesting to explore and might eventually be very helpful. There's a lot that's unknown about the process, however, and it's not widely available. In some countries, it’s used only in special circumstances at the moment.

Bacteriophages attached to the outside of a bacterial cell.

Bacteriophages attached to the outside of a bacterial cell.

The History of Phage Therapy

The credit for the discovery of bacteriophages is given to two different men. In 1915, an English scientist named Frederick Twort published a paper about a bacteriolytic agent that he had discovered. In 1917, a self-taught Canadian scientist named Felix d'Herelle announced that he had discovered a microbe that killed bacteria. Both Twort and d'Herelle had discovered bacteriophages.

Felix d'Herelle started using phage therapy to treat humans in 1919. Other people soon did the same. The therapy had some success but was often ineffective. Scientists didn't know enough about phages to use them properly.

Phage therapy lost its importance in the west when antibiotics were discovered. However, Felix d'Herelle met some Soviet scientists who were interested in using phages to treat infections and helped them to establish the Eliava Institute in Georgia. This institute specializes in phage therapy research and still exists today. The therapy is popular in Georgia and seems to frequently be successful. Though Georgia was once part of the Soviet Union, today it's an independent country.

Antibiotics are a big hammer. You want a guided missile.

— Michael Schmidt, Medical University of South Carolina

How May the Therapy Work?

One potential advantage of phage therapy compared to antibiotic therapy is that the treatment is much more specific. A phage attaches to one particular strain of bacteria and leaves others untouched. Antibiotics may kill not only harmful bacteria but also some of the helpful bacteria that live in our gut.

The specificity of phage therapy may also be a disadvantage, however. If the phage administered for an infection is the wrong type, it will be ineffective. This is why Georgian scientists administer a mixture or "cocktail" of phages that have been known to help a specific type of infection in the past to increase the likelihood of a successful treatment.

The phage cocktail is administered in several ways. For example, to treat a stomach upset, the cocktail is swallowed. To treat a mouth infection, it's used as a mouthwash. To treat an infected skin wound, it's placed on the wound. Infections can be tested to see what bacteria are present, but cocktails for common infections are kept in clinics.

Bacteriophage Therapy

Effectiveness and Safety

Information that is reaching the west from Georgia suggests that phage therapy is helpful, but western scientists have to do their own research to submit to their health regulatory agencies. Scientists and health agencies want to see the results of clinical trials that follow rigorous scientific procedures before they accept claims that phages can treat disease and that they are safe to use.

Some scientists predict that phage therapy may work for a while, but eventually bacteria will become resistant to phages just as they have to antibiotics. Others say that this isn't likely, since unlike antibiotics viruses contain genes and will change their characteristics when their genetic composition changes. As in bacteria, viruses can pick up genes from other sources and genes can change due to mutations. Phages may develop genetic changes that enable them to overcome bacterial resistance, according to some scientists.

Even if phage therapy works for only a while, some researchers say that investigating the therapy is worth the effort. Phages may relieve discomfort and even save human lives while giving scientists the time they need to discover new treatments for bacterial infections.

Once phages have killed bacteria, the immune system removes the phages and dead bacteria from the body. This process is so efficient that some phages are destroyed before they've done their job. Researchers are trying to solve this problem.

Phage Therapy in the Future

Scientists are not only testing phages to see if they fight infections but are also exploring ways to make phage therapy even more effective and safe. For example, in some cases enzymes produced by cells infected with phages seem to be helpful, which means that the enzymes could be used instead of the whole phage.

Some researchers are investigating ways to prevent the manufacture of an enzyme that breaks the bacterial cell open after new phages are made. Bacteria often contain harmful endotoxins, which could produce unpleasant symptoms when they're released. Scientists have discovered that in at least some cases a bacterial cell is killed while the phage DNA is inside the bacterium. Therefore it's not necessary for the bacterial cell to burst (from a human's point of view).

Experiments using phages in lab equipment suggests that some may be especially useful in the removal of bacterial biofilms. These films are made of a layer of bacteria attached to a surface and covered by a protective polysaccharide slime. Bacteria in biofilms are much harder to attack than free bacteria.

Bacterial Biofilms

A Potentially Significant Announcement

In April 2017, a major announcement was made in the United States. Doctors at the University of California in San Diego reported that with the aid of many scientists they had successfully treated a patient with phage therapy. The patient had been near death due to an infection by a multidrug-resistant bacterium. There was apparently nothing else that the doctors could do to help him.

The doctors obtained phage strains from multiple organizations. In the lab, these strains had shown that they could fight the bacterium infecting the patient. The FDA (Food and Drug Administration) gave the doctors permission to administer the mixture of phages. The patient gradually recovered from the infection, though the recovery wasn't straight forward.

Two or three days after phage treatment was started (reports about the time vary), the patient woke from his coma. Later, however, the bacterium seemed have to have become resistant to the phages. Doctors overcame this hurdle by administering new phage strains as well as antibiotics. Eventually there was no evidence of the bacterium in the patient's body, and he was able to go back to work.

At time of the patient's recovery, doctors emphasized that the therapy involved just one patient and they don't know the details about how the phages helped him. Since that time however, at least five additional patients have been cured of serious bacterial infections by the administration of a phage cocktail. The FDA allowed the treatments because the illnesses were emergencies and no approved treatments were available.

Effective Phage Treatment

In June 2018, the University of California, San Diego announced the creation of the Center for Phage Applications and Innovative Therapeutics. The center won't manufacture phage treatments but has connections to places that do. It will support treatments and clinical trials involving phage therapy.

More Phage Therapy News

In 2019, a British teenager with cystic fibrosis who was near death from a bacterial infection was given a phage cocktail. The bacterium that had infected her was Mycobacterium abscessus. All of the available treatments had failed to help her.

The cocktail enabled the teenager to recover in the sense that she was able to live a good life, but the infection wasn't completely removed from her body. She still needed to take a daily phage cocktail, but the infection was under control. The news report said that her parents were hoping for another phage to be added to the mixture in order to cure the infection.

In 2020, a woman who had experienced a kidney transplant was helped by phage therapy in San Diego. The women developed an infection by a multidrug-resistant form of Escherichia coli. Her doctor decided to treat her with phages. Her symptoms gradually improved, and the bacterium disappeared from her body. She later developed some inflammation, but tests showed that the bacterium hadn’t returned. The UC San Diego website says that other people have been helped by phage therapy in their tests. The seventh reference below has links to articles about these people.

Administering the Viruses

The need for a phage cocktail is a problem in western countries. At the moment, some regulatory agencies want safety tests to be done for each type of phage in a mixture. In addition, cocktails for different diseases will need to be updated as bacteria and viruses change genetically or as new strains of bacteria are imported into a community. It would be expensive and time consuming to get each new strain of phage tested every time a cocktail changes. This is one problem that needs to be solved before phage therapy becomes widespread.

Doctors in North America can't yet prescribe phages as they do antibiotics. They may eventually be able to do do, however. Phage therapy seems to have great potential and could be a partial or complete answer to the problem of antibacterial resistance. The therapy has been used in some parts of the world for over ninety years. It's certainly worth investigating. It would be wonderful if it helps us defeat the troublesome and dangerous bacteria that attack us.

References and News Resources

  • Antibiotic resistance facts from the Centers for Disease Control and Prevention (CDC)
  • Bacteriophage information from the University of South Carolina School of Medicine
  • Phage therapy is revitalized from the Nature journal
  • Phage therapy successfully used on a US patient from the University of California, San Diego.
  • A UK case of phage treatment from BBC News
  • Phage therapy for a kidney transplant patient from the UC San Diego School of Medicine
  • Exploring phage applications via the latest news from the UC San Diego School of Medicine
  • Latest reports about phage therapy from the news service (This site collects news releases about the therapy and posts them in a sequence, starting with the most recent release.)

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2013 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on September 11, 2017:

Thank you, Tomp.

Tomp on September 11, 2017:

Nice piece

Linda Crampton (author) from British Columbia, Canada on February 25, 2015:

You've raised some very good points, AVailuu. Antibiotic resistance is certainly scary. Anything that can help the situation is wonderful! I hope researchers investigate phage therapy more thoroughly.

Ashley Vailu'u from Central Texas on February 25, 2015:

Phage therapy is a very interesting idea that I'd never considered before, bacteria eating viruses. I wonder if they could possibly become residential microflora? You said that sometimes the immune system flushes them out of the body before they could serve their purpose. I wonder if their location on the body, or even the body's pH balance, contribute to that phenomenon. Perhaps once we have a better understanding of the relationship between the phages and our bodies, we'll be able phage supplements, like probiotics! (Assuming they would remain symbiotic to our systems, and not eat all of our healthy gut bacteria.)

Antibiotic resistance is a very real threat to our civilization, a lot of that has to do with how strongly we depend on them . I'm interested in anything that may aid our immune systems in fighting the great micro war against illness!

Linda Crampton (author) from British Columbia, Canada on March 31, 2013:

Hi, Deb. The mutations and genetic changes that happen in viruses will be random (unless scientists give them certain genes, which they already do in biotechnology). The prediction is that by chance at least some of the genetic changes that develop in viruses will help them overcome bacterial resistance, allowing them to reproduce. This is just a prediction, though. Whether it will actually happen remains to be seen!

Deb Hirt from Stillwater, OK on March 31, 2013:

From what you have said, it appears that phages will eventually be able to do their own mutations in order to eradicate a specific's mutation. I wonder what will happen as the battle plays out, though? Will this create Smart Infections/Viruses?

Linda Crampton (author) from British Columbia, Canada on March 30, 2013:

Thank you for such a lovely comment, Seeker7! I appreciate the comment, the vote and the share very much!! I agree with you - phage therapy is very exciting. Researchers are talking about allowing phages to infect cells in the lab, selecting phages with desired characteristics and then using them for therapy. It will be very interesting to see how it all works out, assuming phage therapy becomes widely used.

Helen Murphy Howell from Fife, Scotland on March 30, 2013:

This is one of the best health-medical hubs I've read for a long time. Your research is excellent, but more than that, it's written in an easy manner and you keep the interest going beautifully.

Phage therapy has to be one of the most exciting things to happen in medicine for a long time - along with the toxins from snakes and other animals that are being developed.

I wonder if the phages will develop their own evolution in order to keep up with changes that harmful bacteria make? I would imagine within nature this would be too slow for medical purposes, but perhaps there is a way to speed this up naturally?

This was a fascinating and thoroughly enjoyable hub - many thanks for sharing! Voted up + shared.

Linda Crampton (author) from British Columbia, Canada on March 30, 2013:

Thank you for the comment and the vote, drbj! I very much hope that phage therapy is shown to be successful and is approved for use. We badly need something to either help or replace certain antibiotics. The problem of inefficient or ineffective antibiotics is growing.

drbj and sherry from south Florida on March 30, 2013:

Phage therapy may one day reach the adulatory status of antibiotics when they were first introduced. Amazing information, Alicia. Thank you and a large Up!

Linda Crampton (author) from British Columbia, Canada on March 30, 2013:

Thank you very much, wabash annie! I appreciate your comment.

wabash annie from Colorado Front Range on March 30, 2013:

Wow, Alicia, your hub is excellent and there is so much information as well as links to even more. Thanks much for writing about this topic.

Linda Crampton (author) from British Columbia, Canada on March 29, 2013:

Hi, Vicki. It will be very interesting to see whether phage therapy becomes widely used in North America and to see how the therapy develops! Thank you very much for the comment.

Vickiw on March 29, 2013:

Very interesting! I wonder if this will take the place of such widespread antibiotic use that we have now. Incredible to think this was being used in 1917! So glad you did this great research, and wrote this Hub.