Genome Sequences of Brucella Melitensis Strains QH2019001 and QH2019005 Provides Insight Into Different Evolutionary Origins Within Qinghai Province, China

Background: Brucellosis, which is cause by Brucella , is one of the most important zoonoses and is considered a “forgotten, neglected zoonosis” by the WHO. Methods Blood samples were isolated from two brucellosis males that were confirmed B. melitensis positive following multiple loci variable-number tandem repeat analysis (MLVA) and strains QH2019001 and QH2019005 were identified. Genomic DNA was extracted from these samples and whole genome sequencing (WGS) was performed. Next, SNP-based phylogenetic analysis was performed to compare the two strains to 94 B. melitensis strains (complete genome and draft genome) retrieved from online databases. Results The QH2019001 and QH2019005 strains were found to have differences in their variable-number tandem repeats. Phylogenetic examination of the 96 strains assigned them to 5 genotype groups, with QH2019001 and QH2019005 assigned to the same group, but to different subgroups; with the QH2019005 strain assigned to a new subgenotype, IIj. These findings were then combined to determine strain origin. Conclusions Utilizing a whole genome SNP-based approach highlights the diversity between B. melitensis strains, and it can facilitate the elucidation of different evolutionary histories. This approach also revealed that the QH2019005 is part of a new subgenotype with an ancient origin in the eastern Mediterranean Sea.