Molecular-Genetic Characteristics of Yersinia pestis Strains Isolated in the Mongolian Territory of Transboundary Sailyugem Natural Plague Focus

Objective : investigation of phylogenetic origin and affinity of Yersinia pestis strains isolated from field material collected during the epizootiologic survey of the Mongolian part of trans-boundary Sailyugem natural plague focus. Materials and methods : MLVA25-typing of 81 Y. pestis strains, including 55 isolates from the Mongolian part of transboundary Sailyugem natural plague focus, collected in 2017-2018 was carried out. The plague agent strains isolated in different years in the natural foci of Northwest Mongolia and Southern Siberia were used as comparison group. Whole genome sequencing was performed for 21 Y. pestis strains subspecies pestis isolated in Mongolia in 2018 and 1988-1990 and in Gorny Altai of the Russian Federation in 2012-2016. SNP-typing was conducted on the basis of whole genomes of Y. pestis strains identified in the current research and also genomes from GenBank international database. Search of single nucleotide polymorphisms in Y. pestis genomes was carried out in two ways: by means of snippy v. 4.3.5 software and using mummer v. 3.1 package and a set of the author’s scripts. Phylogenetic reconstruction was conducted with the help of RAxML method. Results and discussion: Results of MLVA25 typing of Y. pestis subsp. pestis demonstrated that the strains isolated in Mongolian and Russian parts of the Sailyugem and Khuukh-Serkh-Munkh-Khairkhan natural foci belong to one common cluster. SNP-typing placed the studied isolates from the Mongolian and Russian territories into 4. ANT phylogenetic line with high level of reliability which testifies to the genetic similarity of the specified pathogen groups. The data of MLVA- and SNP-typing showed insignificant variability of the plague agent in the territory of the Mongolian part of trans-boundary Sailyugem natural plague focus. On the basis of the conducted research and results of epizootiological monitoring of Russia and Mongolia border territories it is possible to draw a conclusion on gradual wide penetration of Y. pestis subsp. pestis mainly into grey marmot settlements in Southeast Altai from Northwest Mongolia.