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Bacteriophages (or phages) are viruses that infect and kill bacteria.
What are the differences between viruses and bacteria?
Bacteria and viruses are two different kinds of organism. Bacteria are microscopic, single-celled organisms that exist almost everywhere. They survive and replicate by metabolising different substances depending on the particular strain of bacteria. Viruses are generally even smaller entities that are the most abundant entities on the planet, existing everywhere you find bacteria. They consist of a package of DNA (or RNA) contained in protein armour. Viruses have to infect host cells with their DNA to replicate, usually killing the host cells in the process.
Are bacteria bad?
Not necessarily. The human microbiome consists of many types of bacteria that help regulate various functions of the human body, from digestion to skin condition. But some bacteria do produce toxins that are harmful to humans - and these are the bacteria we want to kill.
Why not use antibiotics to kill the bad bacteria?
Antibiotics are used widely to kill bad bacteria. However, antibiotics kill bacteria fairly indiscriminately, so have the potential to kill good bacteria as well. The inappropriate use of antibiotics (overprescription or not completing a prescribed course) is driving the increase in antibiotic resistance - the rise of 'superbugs'. Phages could be a solution to both these problems. Specific phages only attack specific bacteria, so the bad bacteria can be targeted while the good bacteria are left alone. In addition, as phages are not antibiotics, bacteria that have evolved antibiotic resistance are still vulnerable to phage attack.
If phages are so good at killing bad bacteria, why are they not in wider use?
This is a very good question, and one that the House of Commons Science, Innovation and Technology (SI&T) Select Committee have been looking into through their Inquiry into the antimicrobial potential of bacteriophages. The resulting report can be accessed here.
The short answer to this question is that much more research needs to be done to allow scientists and clinicians a better understanding of how phages and bacteria interact, and how to ensure any phage therapies developed in future are safe and effective. On a visit to a number of laboratories at UCL, Birkbeck, University of London and the Zayed Centre for Research into Rare Disease in Children, SI&T Select Committee members saw first-hand the potential of phages as a solution to antimicrobial resistance, but also the research and infrastructure challenges that need to be overcome to develop phage therapies for clinical use.
