Viruses that infect and kill bacteria….
New strains of infection causing bacteria are constantly propping up. At the same time antibiotics are losing their effectiveness towards presently existing bacteria. Scientists are constantly looking for new ways to combat infections by trying new antibiotics, using combination drugs or changing the dosage of antibiotics currently available.
A new less popular method is making a comeback. The antibiotic resistance crisis can be fought by killing disease causing bacteria with help of viruses. Like any other organisms cell gets infected by bacteria, bacterial cells can be also attacked by carefully selected specific virus called bacteriophages (phage shortly). These phages act by killing bacteria by incorporating them in their lifecycle.
Phage action
Bacteriophage or ‘bacteria-eater’ where first independently discovered by Frederick W. Twort in Great Britain and Félix d’Hérelle in France.
They act by attacking the bacteria, inserting its genetic material (DNA), replicating and finally lyses (bursts open) the cell wall destroying it. As a type of virus, phages cannot live and reproduce alone. Generally phages start their killing action by recognising their host bacteria and attaching itself to a specific site on it. The phages then enters to inject its DNA through bacterial cell wall. The DNA now makes multiple copies of self by parasitically using bacterial cell nutrients as fuel. Each of the DNA then raps a cell wall around itself. Finally the phages release toxic substances to kill the bacteria and release even more virus looking for host like that of parent bacteria.
Soon after making their discovery, Twort and d’Hérelle began to use phages in treating human bacterial diseases such as bubonic plague and cholera. However the phage therapy was abandoned due to World War 1, shortage of funds and discovery of antibiotics. With the rise of antibiotic-resistant bacteria, however, the therapeutic potential of phages has received renewed attention.
Why world needs Phage therapy
Phage therapy has many advantages over the antibiotic treatment. Antibiotics work by failing one of the biological cycle of the bacteria. Since they are not specific in their action antibiotics indiscriminately kills the natural ecosystem of even healthy bacteria found in the gut and on the skin of humans. Since phages are specific for a kind of bacteria this shortcoming of antibiotics could be easily overcome. Again the phages can act on antibiotic-resistant bacteria too. Any kind of confrontation developed by the bacteria (bio-films) against the bacteriophage won’t stop the virus from homicide. But finding, isolating and developing pure- right concentration- phage specific for a bacteria is a time consuming process for by now very ill patients. If not prepared cleanly human body can trigger a deadly immune response triggering a cascade of changes that can damage multiple organ systems, causing them to fail. But that’s not the end of the problems. Phages don’t simply diffuse to the site of infection and is likely to be attacked by body’s immune system too.
The new study where phages were found functional
A US-based team of researchers used phage therapy to treat antibiotic-resistant pneumonia. Using a bio degradable polymer and a sublime chemical the researchers produced right sized shells carrying the phages in it. Due to the precise size of shell enclosed phages could be delivered at the site of infection without triggering bodies white blood cells immune response. These when inhaled by mice infected with Pseudomonas aeruginosa (causing lung infections) dropped infection levels by a factor of 10. While only 13 percent of untreated mice survived the infection, all of the phage-treated mice survived.
All of this looks incredibly promising. May be in the near future, as antibiotics lose their effectiveness phage therapy might move to our first resort against all antibiotic-resistant bacterial infections.
