Phylogeographical Analysis of Anthrax Microbe Strains Isolated in the Central Federal District in 2023

The aim of the work is to determine an evolutionary and phylogeographic origin of Bacillus anthracis strains that caused large-scale outbreaks of anthrax in the Central Federal District in 2023. Materials and methods . Whole genome sequencing of 13 strains of the anthrax pathogen isolated in the Ryazan and Voronezh Regions was performed. It was conducted using the Ion GeneStudio S5 Plus System (Life Technologies, USA) and DNBSEQ-G50 (MGI, China) high-throughput sequencing platforms. A whole-genome SNP analysis of 1245 Bacillus anthracis strains from 50 countries, including 304 strains from 44 constituent entities of the Russian Federation, was carried out. Results and discussion . It has been established that the anthrax strains isolated in the Central Federal District in 2023 fall under the phylogenetic branch A.Br.117, which belongs to the monophyletic clade TEA Tsiankovskii. Strains 1394, 1395 (Ryazan Region), 1402, 1404 (Voronezh Region, Paninsky District) belong to the genotype A.Br.117-2, and strains 1405–1420 (Voronezh Region, Bogucharsky District) – to the genotype A.Br.117-4. The strains that caused the cases of the disease in Paninsky District have a common origin with strains 988/717 and 546/714 isolated in the region in the 1980–1990s, and the strains from Bogucharsky District are phylogenetically close to strain 991/178 isolated in 1991 in Dnepropetrovsk Region of Ukraine. The most detailed, to date, topology of the phylogenetic branch of A.Br.117 is described, including four genotypes for which probable time intervals of divergence are determined and the features of the phylogeographic distribution of 165 B. anthracis strains are provided. Strains belonging to the genotype A.Br.117-1 were isolated in Moldova and Ukraine, strains of the genotype A.Br.117-2 predominate in the Central and Southern Federal Districts; strains of genotype A.Br.117-3 – in the Volga, Southern and North Caucasian Federal Districts, and strains of genotype A.Br.117-4 – in the North Caucasian and Southern Federal Districts.