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In China, brucellosis is an endemic disease typically caused by Brucella melitensis infection (biovars 1 and 3). Brucella canis infection in dogs has not traditionally recognized as a major problem. In recent years however, brucellosis resulting from Brucella canis infection has also been reported, suggesting that infections from this species may be increasing. Data concerning the epidemiology of brucellosis resulting from Brucella canis infection is limited. Therefore, the purpose of this study was to assess the diversity among Chinese Brucella canis strains for epidemiological purposes. First, we employed a 16-marker VNTR assay (Brucella MLVA-16) to assess the diversity and epidemiological relationship of 29 Brucella canis isolates from diverse locations throughout China with 38 isolates from other countries. MLVA-16 analysis separated the 67 Brucella canis isolates into 57 genotypes that grouped into five clusters with genetic similarity coefficients ranging from 67.73 to 100%. Moreover, this analysis revealed a new genotype (2-3-9-11-3-1-5-1:118), which was present in two isolates recovered from Guangxi in 1986 and 1987. Second, multiplex PCR and sequencing analysis were used to determine whether the 29 Chinese Brucella canis isolates had the characteristic BMEI1435 gene deletion. Only two isolates had this deletion. Third, amplification of the omp25 gene revealed that 26 isolates from China had a T545C mutation. Collectively, this study reveals that considerable diversity exists among Brucella canis isolates in China and provides resources for studying the genetic variation and microevolution of Brucella. [ABSTRACT FROM AUTHOR]

The Brucella melitensis vaccine strain M5 is widely used to prevent and control brucellosis in animals. In this study, we determined the whole-genome sequence of M5, and conducted a comprehensive comparative analysis against the whole-genome sequence of the virulent strain 16 M and other reference strains. This analysis revealed 11 regions of deletion (RDs) and 2 regions of insertion (RIs) within the M5 genome. Among these regions, the sequences encompassed in 5 RDs and 1 RI showed consistent variation, with a large deletion between the M5 and the 16 M genomes. RD4 and RD5 showed the large diversity among all Brucella genomes, both in RD length and RD copy number. Thus, RD4 and RD5 are potential sites for typing different Brucella strains. Other RD and RI regions exhibited multiple single nucleotide polymorphisms (SNPs). In addition, a genome fragment with a 56 kb rearrangement was determined to be consistent with previous studies. Comparative genomic analysis indicated that genomic island inversion in Brucella was widely present. With the genetic pattern common among all strains analyzed, these 2 RDs, 1 RI, and one inversion region are potential sites for detection of genomic differences. Several SNPs of important virulence-related genes (motB, dhbC, sfuB, dsbAB, aidA, aroC, and lysR) were also detected, and may be used to determine the mechanism of virulence attenuation. Collectively, this study reveals that comparative analysis between wild-type and vaccine strains can provide resources for the study of virulence and microevolution of Brucella. [ABSTRACT FROM AUTHOR]

In China, brucellosis is an endemic disease and the main sources of brucellosis in animals and humans are infected sheep, cattle and swine. Brucella melitensis (biovars 1 and 3) is the predominant species, associated with sporadic cases and outbreak in humans. Isolates of B. abortus, primarily biovars 1 and 3, and B. suis biovars 1 and 3 are also associated with sporadic human brucellosis. In this study, the genetic profiles of B. melitensis and B. abortus isolates from humans and animals were analyzed and compared by multi-locus variable-number tandem-repeat analysis (MLVA). Among the B. melitensis isolates, the majority (74/82) belonged to MLVA8 genotype 42, clustering in the ‘East Mediterranean’ group. Two B. melitensis biovar 1 genotype 47 isolates, belonging to the ‘Americas’ group, were recovered; both were from the Himalayan blue sheep (Pseudois nayaur, a wild animal). The majority of B. abortus isolates (51/70) were biovar 3, genotype 36. Ten B. suis biovar 1 field isolates, including seven outbreak isolates recovered from a cattle farm in Inner Mongolia, were genetically indistinguishable from the vaccine strain S2, based on MLVA cluster analysis. MLVA analysis provided important information for epidemiological trace-back. To the best of our knowledge, this is the first report to associate Brucella cross-infection with the vaccine strain S2 based on molecular comparison of recovered isolates to the vaccine strain. MLVA typing could be an essential assay to improve brucellosis surveillance and control programs. [ABSTRACT FROM AUTHOR]