First report of the isolation, characterization, and genotyping of Brucella abortus biovar 9 in Brazil.

Brucellosis is a globally important zoonosis that causes significant economic and social losses due to its impact on livestock productivity and the risk of human infection. Given its importance, the characterization of field isolates at the species, biovar, and genotypic levels allows for the tracking of potential new sources of infection and the introduction of new strains into a given region or herd. This study aimed to phenotypically and genotypically characterize three field isolates of Brucella abortus biovar 9 and to sequence their genomes for public availability in a genomic database. To date, this biovar had never been reported in Brazil, and only rare reports exist worldwide. All isolates exhibited phenotypic characteristics consistent with biovar 9. Genotyping using Multiple Locus Variable Number Tandem Repeat (VNTR) Analysis (MLVA16) revealed that all strains belonged to genotype 40 in MLVA16 panel 1, a genotype not previously identified in the Brazil. Whole-genome single-nucleotide polymorphism (wgSNP) analysis showed high genetic similarity among the three isolates, which differed from the reference strain by an average of 425 SNPs. According to the information provided by the official state agency, it was not possible to determine the probable sources of infection of this newly identified biovar of Brucella abortus; however, these findings provide valuable information to support future surveillance and control strategies.