Naturally occurring viruses called bacteriophages (from the Greek meaning ‘bacteria-eaters’) are harmless to people but lethal to bacteria. When a phage encounters its prey, it latches onto the outside and injects its own DNA inside the cell. This reproduces inside the bacterium and then the ‘daughter phages’ burst through the cell walls, before latching onto more bacteria and repeating the cycle until all the bacteria have been killed – and the infection has been dealt with.
First discovered by two different scientists – the Briton Frederick Twort in 1915 and the French-Canadian Felix d’Herelle in 1917, but it was d’Herelle who pioneered phage therapy. Abandoned in the west when antibiotics were discovered and came into common use in the 1940s. In Stalin’s Soviet Republic however, access to antibiotics was limited, so phage therapy continued and a phage therapy centre founded in Tbilisi, Georgia, became a leading centre for phage research.
Unlike antibiotics, which target a broad range of bacteria, each phage kills only one type or strain, so scientists begin by taking bacterial samples from patients and finding a phage from the lab that can kill that particular bacteria. It is much harder for bacteria to develop resistance to phages due to their diversity, their ability to evolve and their sheer abundance. Bacteriophages are actually the most abundant life form on earth – there are far more phages than there are stars in the visible universe. So if bacteria evolve to resist a particular phage, the scientists simply turn to their extensive phage library, or to nature, to find another. They also create what are known as ‘phage cocktails’ – mixtures of different phages that attack bacteria from different angles and make it much more difficult for them to develop resistance.
Currently phage therapy is not approved or regulated in the west and this is the next big challenge. The good news is that the first large scale, western standard clinical trials have now begun, so hopefully in future we see this incredible 100 year old therapy returning to Europe to help us beat the superbugs.
Related links
Could viruses called bacteriophages be the answer to the antibiotic crisis? BBC 2 Trust me, I'm a Doctor, Series 5, Episode 1 (1 Sep. 2016).
