The Enemy of My Enemy
✇ Nearly 125 years ago, a British bacteriologist observed that the holy waters of the Ganges and Yamuna had curious bactericidal properties, limiting the spread of cholera. It took another 20 years before two microbiologists independently proposed the existence of viruses. Observing small clearings on a lawn of dysentery-causing bacillus on an agar plate, d’Herelle coined the term bacteriophage for the virus that devours bacteria; now affectionately abbreviated to “phage”.
✇ A Voracious Appetite: Found everywhere bacteria exist- in the soil, deep inside the earth’s crust, within the bodies of animals and plants, and densely packed in the oceans, there are an estimated 1×10^8 different types of phages, each infecting only a specific type of bacteria. Almost comical in appearance, a phage has its genetic material tightly packed into the capsid head, that can be injected through the stalk-like tail into the bacterial cell. Once inside, it can stage a peaceful coup (lysogenic) or burst open the bacterium (lytic) when it multiplies. It is estimated that there are up to 10^32 phages in our biosphere, destroying half the bacterial population every 48 hours!
✇ Microbe Hunters: d’Herelle and his fellow scientists were quick to grasp the potential of phages as antibacterials. After consuming a preparation to confirm its safety, he administered the phage to a 12-year old boy with acute dysentery. The boy fully recovered. This set off a golden era in the commercial production and use of phages, centered largely in eastern Europe and Russia. In the 1940’s, companies like L’Oreal and Eli Lilly marketed products with catchy names like Bacté-coli-phage and Staphylo-gel! There were set backs (d’Herelle’s science partner in Tbilisi was executed by Stalin) and with the discovery of antibiotics in the 1940’s, Western scientists lost interest in this line of medical research. Unfortunately, most published studies (written in Russian or Georgian) are not accessible to the western world and clinical trials did not follow current protocols of controls, making them difficult to assess retrospectively.
✇ Evolutionary Arms Race: With growing resistance to antibiotics, a resurgence in phage therapy may be warranted. One advantage to phage therapy is that when bacteria develop resistance to a phage, we should be able to rapidly select (in a few days or weeks) for mutant phage versions in a tit-for-tat evolutionary arms race! Phage therapy is already around us in some form:the USDA has approved a phage spray (ListShield) that can be used on cheese, chicken, and processed meat to prevent infection with Listeria. Is this the start of a new phage in the way we treat bacterial infections? 🙂
Image: T-phage infecting E. coli , false-colored EM via http://goo.gl/fmDVCi