Bacteriophages: weapons against bacteria
A recent BBC Radio 4 programme introduced an interesting alternative to antibiotics for treatment of bacterial infections. This was to use viruses that naturally infect the bacteria that infect us.
Most people have probably heard the term ‘antibiotic resistance‘, but they may be less familiar with what it means, how much of a problem it is, and what is being done about it. The problem is bacteria are becoming more and more resistant to the antibiotics we throw at them. This is through misuse by patients and by over prescribing by doctors. If a patient does not finish a course of antibiotics, the resistant bacteria may survive, multiply and spread. To exacerbate the issue, no new classes of antibiotics have been found since 1987.
England’s Chief Medical Officer Professor Dame Sally Davies recently published a book suggesting that we are facing an ‘apocalyptic’ threat from antibiotic resistant superbugs. The World Health Organisation has estimated that antibiotics, on average, add 20 years to our lives. Dame Davies’ solution would be to increase hygiene measures in hospitals, to limit the current use of antibiotics, and to make it a priority to find new antibiotics.
In the past, new antibiotics have been found by looking amongst the bacteria themselves and the mechanisms they use to attack one another. However, another natural source and a potential alternative to traditional antibiotics would be to look at viruses that infect bacteria. Viruses that specifically infect bacterium are known as bacteriophages.
Dr Martha Clokie from The University of Leicester has been carrying out research into bacteriophages and their phage-derived products, which could be used to treat antibiotic resistant bacterial infections such as Clostridium Difficile. In an interview for BBC Inside Science Dr Clokie described how bacteriophages were discovered in the early 1900s, and were commonly used in Russia until the 1980s. In the West, bacteriophages were used until about the 1940s, but as soon as antibiotics were discovered their use was phased out. This was because antibiotics were seen as being much less complicated to use.
The very thing that led to their disuse – their specificity – is one reason why bacteriophages could be such a good alternative to antibiotics. The specificity of a bacteriophage for a particular species of bacteria means that phages have fewer side effects than antibiotics. For example, when you take antibiotics to cure an infection in the gut, the antibiotic will kill many of the non-pathogenic commensal bacteria normally found in the gut, as well as the bacterium that was causing the problem. Wiping out gut commensal bacteria could allow more sinister strains to take their place. The non-pathogenic bacteria that normally reside in the gut, work in synergy with the body aiding digestion, and playing a role in gut immunity. Therefore, the specificity of bacteriophages is now seen as a benefit.
A large amount of research is being carried out to determine how bacteriophages target bacteria, how they kill them, and what proteins they express that block different parts of bacterial growth. The focus of much of the research is to identify bacteriophages or phage proteins that target bacteria, which are known to have developed resistance to certain antibiotics. Examples of resistant bacteria include Pseudomonas aeruginosa, Clostridium Difficile, methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli.
Bacteriophage research has already reached the clinic. Clinical trials are underway using phages for treatment of chronic ear infections caused by antibiotic resistant Pseudomonas aeruginosa. There is a good chance that in the next 10 years, we could be given a bacteriophage by our GP rather than a traditional antibiotic to treat well known bacterial infections.