Genotypic heterogeneity and geographical diversity of collection strains of Francisella tularensis according to the data of VNTR analysis of their DNA

The distribution of variable tandem repeats in four loci (FtA, FtB, FtC, and FtD) in 352 strains of Francisella tularensis of different subspecies, isolated in various regions of the world during the period from 1941 to 2004, was studied. The variability of the VNTR loci was evaluated using the Ney diversity index (DI). An analysis of the identified genotypes of the strains made it possible to group them into 61 variants from A to I with frequencies of encounter from 0.002 to 0.142, while cluster analysis made it possible to distribute them among nine clusters with different numbers of components. The real existence of genotypic heterogeneity and geographical diversity among them, as well as the territorial coordination of definite types of strains, were demonstrated. In order to conduct a territorial and spatial analysis of the distribution of genotypes of the strains studied, we developed a geoinformational system (GIS), “Tularemia.” A characteristic feature of the GIS developed is a dynamic mode of operation, expressed in the possibility of constant addition of information not only by supplementation of already existing data but also by the creation of new layers. Any new input of information is dynamically incorporated into the GIS, which makes it possible to perform both retrospective and operative analysis. The “Tularemia” geoinformational system should find its place in the structure of the epidemiological method, the use of which will make it possible to bring the epidemiological surveillance of tularemia to a qualitatively higher level.