Treatment consists of identifying the strain of bacteria infecting the patient and injecting the phage, or bacteriophage to give them their scientific name, that will in turn infect the bacteria, reproduce inside it until number of phages are such that the membrane of the bacteria breaks, freeing the other phages to attack neighbouring bacteria and so on until there are none left.
The singularity of a particular phage to attack an individual bacteria means that there are no side effects on human cells or those bacteria essential to the organism. Of the millions of phages that exist in the biomasse, only some 5000 have been identified, the research centre in Tbilisi collects its raw material from the nearby river before testing it's ability to kill specific bacteria inside a petri dish. They have yet to find a bacteria with no phage capable of destroying it.
Western medicine has largely forgotten phagotheraphy since the development of antibiotics, which are deemed easier to manipulate and to conserve. Today's health and safety standards for developing medicaments and human fear of treating people with living organisms rather than inert molecules mean that a reintroduction of phages would be ideologically difficult. The relative cheapness to produce phages and the difficulty for a pharmaceutical company to put an industrial copyright on a non-transformed product obtained from nature means that the financial rewards are not inducive to research.
Carl De Keyzer 2005