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Background: Brucellosis incidence in China is divided into three stages: high incidence (1950s-1960s), decline (1970s-1980s), and re-emergence (1990s-2010s). At the re-emergence stage, Brucellosis incidence grew exponentially and spread to all 32 provinces. We describe the magnitude and the etiological distribution changes in mainland China by genotyping data and emphasize its recent reemergence. We also provide the genetic diversity and molecular epidemiological characteristics of Brucella., Results: From a total of 206 Brucella isolates, 19 MLST genotypes (STs) were identified and 13 new STs(ST71-83)were found. MLST grouped the population into three clusters. B. melitensis, B. abortus and B. suis were grouped into cluster 1, 2 and 3 respectively. The predominant genotype in the first cluster by MLST, remained unchanged during the three stages. However, the proportion of genotypes in the three stages had changed. More isolates were clustered in ST8 at the re-emergence stage. STs71-74, which were not found in the two former stages, appeared at the re-emergence stage., Conclusions: The changing molecular epidemiology of brucellosis improve our understanding of apparent geographic expansion from the historically affected north of China to southern provinces in recent reemergence.

Background: Brucellosis is a bacterial disease caused by Brucella infection. In the late fifties, Brucella suis vaccine strain S2 with reduced virulence was obtained by serial transfer of a virulent B. suis biovar 1 strain in China. It has been widely used for vaccination in China since 1971. Until now, the mechanisms underlie virulence attenuation of S2 are still unknown., Results: In this paper, the whole genome sequencing of S2 was carried out by Illumina Hiseq2000 sequencing method. We further performed the comparative genomic analysis to find out the differences between S2 and the virulent Brucella suis strain 1330. We found premature stops in outer membrane autotransporter omaA and eryD genes. Single mutations were found in phosphatidylcholine synthase, phosphorglucosamine mutase, pyruvate kinase and FliF, which have been reported to be related to the virulence of Brucella or other bacteria. Of the other different proteins between S2 and 1330, such as Omp2b, periplasmic sugar-binding protein, and oligopeptide ABC transporter, no definitive implications related to bacterial virulence were found, which await further investigation., Conclusions: The data presented here provided the rational basis for designing Brucella vaccines that could be used in other strains.