Bacteriophages (or phages) are viruses which will only infect and kill bacteria and are completely harmless to plants, animals and humans. They are the most numerous organisms on the planet and it is estimated there are 100 times as many phages in the human body as there are human cells.
Globally, there are estimated to be as many as 1031 (10 followed by 31 zeros) phages in the biosphere and, despite their small size, if their mass is combined it would be 1000 times the mass of all the elephants on the planet. Phages are natural predators of bacteria and will infect their host, replicate and release sometimes over 100 progeny which can then repeat the infection process.
They are also much more specific than chemical antibiotics and can eliminate only pathogenic bacteria while leaving the rest of the ecosystem intact.
Phages were first identified over 100 years ago and their ability to very specifically infect and kill bacteria led to the suggestion that they could be used for the treatment of disease.
A number of studies confirmed the beneficial effect of phages but the discovery and wide-scale industrial production of small-molecule chemical antibiotics (such as penicillin) essentially eliminated their use in the West.
At the time, the biological nature of phages was not well understood and the relative ease of application and industrial potential of chemical antibiotics relegated phages to the side-lines.
The main exception to this was in the former Soviet Union and annexed territories, particularly in Georgia where the Eliava Institute has been using phage therapy successfully for almost 100 years, and in Poland where the Hirszfeld Institute has been using phage therapeutically for several decades.
However, phages, as biological materials, do have some features which have prevented their wide-spread application. Most notably:
1. they can lack stability and therefore often need to be stored at 4°C and
2. as naturally occurring organisms, they are difficult to protect by traditional IP, making their commercial development more difficult.