Phylogeny of Brucella abortus strains isolated in the Russian Federation

Abstract

Objective: To study Brucella (B.) abortus strains isolated in the Russian Federation, in order to identify their detailed position in the phylogenetic structure of the species global population as well as to determine genetic relationships for isolates from different geographical areas. Methods: Based on Bayesian method, the whole genome single-nucleotide polymorphism (SNP) analysis of 258 B. abortus strains from different geographical areas of the world including 20 B. abortus strains isolated in Russia was carried out. Results: The core genome SNP analysis of the B. abortus isolates allowed describing the main genetic lineages. The Russian strains entered two separate clades, including the basal branch and the C1 branch that is widely spread in Eurasia. The data on the isolation time was used for the dating of phylogenetic tree, and also the estimated time frame for the B. abortus genotype diversification was determined. There were sets of specific SNPs identified, which defined each of the genotypes and sub-genotypes. Conclusions: A significant genetic diversity of the brucellosis pathogen strains from Russia has been proven. The sets of unique specific SNPs described in our study may become one of the elements within a bio-informational analysis algorithm to be used for epidemiological study of brucellosis outbreaks, including those caused by new (atypical) genetic variants of B. abortus.

Brucella abortus in Kazakhstan, population structure and comparison with worldwide genetic diversity

“…All these processes might have constituted opportunities for a wide distribution of European strains of B. abortus in Kazakhstan, but it is important to note that essentially subclade C1 strains contaminate Kazakhstan whereas Western Europe is associated with subclade C2. Subclade C1 is common in North Caucasus ( Kovalev et al, 2021 ). At the same time, the disastrous large-scale collectivization carried out in 1929–1933 resulted in a four-fold reduction in the local cattle population ( Zhumasultanova, 2021 ), which could lead to a reduction in the historically circulating strains of B. abortus .…”

“…Figure 4 shows an enlarged view of the subclade C1 lineages containing the Kazakhstan strains, together with the region of origin of the strains. Most strains from Kazakhstan appeared to be closest to strains from neighboring Russia and Georgia (Sidamonidze et al, 2017;Kovalev et al, 2021). For instance, the unique branch F representative from Kazakhstan, Kaz021 isolated in 2015, is surrounded in Figure 4 by multiple strains from Russia (North Caucasus) and Georgia.…”