Genetic characterization of Brucella melitensis isolates from Mongolia, Russia, and Azerbaijan

The goal of this work was to provide a comparative genetic characterization of human and animal Brucella melitensis isolates from Mongolia, Russia, and Azerbaijan using the available molecular-genetic typing methods. Twenty eight Mongolian (n = 18), Russian (n = 6), and Azerbaijanian (n = 4) human and animal B. melitensis isolates were studied using two molecular typing methods based on PCR for differential species- and biovar-specific open reading frame (ORF) molecular targets and multiple-locus variable-number tandem-repeats analysis (MLVA) using primers to 12 known loci. All B. melitensis isolates were identified as the B. melitensis biovar 2 by PCR for differential molecular targets. The MLVA revealed seven identical and five variable MLVA loci. All isolates were classified and divided into 25 genotypes using the dendrogram based on the data of 12 loci and a cluster related to the reference strain B. melitensis 63/9 biovar 2. The B. melitensis isolates related to MLVA genotypes were connected to Mongolian, Russian, and Azerbaijanian regions. The circulation of two isolates was determined in nontypical hosts (camels and yaks) for B. melitensis. The genetic characteristics of geographically distant B. melitensis isolates from Mongolia, Russia, and Azerbaijan have determined their relationship. The MLVA method has shown the genetic diversity of the isolates belonging to 25 genotypes with a Hunter and Gaston discriminatory index (HGDI) of 0.9841. To improve the system of brucellosis surveillance in Russia, MLVA typing of B. melitensis isolates obtained from neighbouring territories both with Mongolia (Republics of Tuva, Buryatia, and the Irkutsk region) and southern regions (Republics of Dagestan, Kalmykia and the Stavropol region) is required.