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Phage-typing.

Phage-typing is a technique for identifying sources of infection when monitoring the environment and, in particular, water bodies. Its essence lies in the labeling of infectious bacterial strains using bacteriophages. In other words, phage typing is necessary to identify bacterial strains that have caused a particular outbreak of infectious diseases , as well as to determine the state of bathing reservoirs or water sources for bacterial contamination.

This method was also used for intraspecific identification of bacterial strains (to determine the phage type of bacteria - phagovar). Why is intraspecific identification of bacteria necessary? When a person has been infected with a certain bacterium, which was sown during bacteriological research, in order to prescribe an effective treatment, it is necessary to know specifically which of the strains of this bacterium (its variety) is present in the human body. For example, there are many varieties of staphylococcus , for which it is difficult to find an antibiotic without knowing their exact phage type. Bacteria of the genus Shigella flexneri, Salmonella, enteropathogenic Escherichia coli and many other bacteria also “suffer” from the same variety of phagovars.

How is phage typing performed? Bacteria of an unknown pathogen or a known pathogen, but its unspecified strain, are inoculated into several dishes with a nutrient medium. In each of them, drops of specific phages, known in advance, are applied. If a culture of bacteria sensitive to a particular phage appears in the dish, then the bacterium (or rather its shell) is lysis , in which it is destroyed. And visible sterile zones appear in the cup. This means that the strain of the bacteria has been identified. If such zones are not formed, then the type of phage launched into the bacterial colony does not correspond to this bacterium.

Phage typing is used in cases of prescribing treatment with bacteriophages for the effectiveness of their use. Bacteriological analysis reveals the presence of a specific type of bacteria in the body, and using phage typing according to the technology described above, it is determined whether the bacteriophage preparation selected for treatment is suitable for a given bacterial strain, whether the pathogenic bacteria will be lysed.

It should be added that the activity of a bacteriophage depends on the degree of its dilution (the concentration of phages in the solution of the bacteriophage preparation), at which the selected sensitive bacterium is completely lysed. It is permissible to dilute finished preparations of bacteriophages, but the best effect of bacterial lysis will be achieved when used in the concentration suggested by the pharmaceutical industry.