Genetic Polymorphism Characteristics of <i>Brucella canis</i> Isolated in China

<div><p>In China, brucellosis is an endemic disease typically caused by <i>Brucella melitensis</i> infection (biovars 1 and 3). <i>Brucella canis</i> infection in dogs has not traditionally recognized as a major problem. In recent years however, brucellosis resulting from <i>Brucella canis</i> infection has also been reported, suggesting that infections from this species may be increasing. Data concerning the epidemiology of brucellosis resulting from <i>Brucella canis</i> infection is limited. Therefore, the purpose of this study was to assess the diversity among Chinese <i>Brucella canis</i> strains for epidemiological purposes. First, we employed a 16-marker VNTR assay (<i>Brucella</i> MLVA-16) to assess the diversity and epidemiological relationship of 29 <i>Brucella canis</i> isolates from diverse locations throughout China with 38 isolates from other countries. MLVA-16 analysis separated the 67 <i>Brucella canis</i> 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 <i>Brucella canis</i> isolates had the characteristic BMEI1435 gene deletion. Only two isolates had this deletion. Third, amplification of the <i>omp25</i> gene revealed that 26 isolates from China had a T545C mutation. Collectively, this study reveals that considerable diversity exists among <i>Brucella canis</i> isolates in China and provides resources for studying the genetic variation and microevolution of <i>Brucella</i>.</p></div

Dendrogram derived from the MLVA-16 genotyping assay.

<p>This dendrogram illustrates the various relationships among the 29 Chinese <i>B. canis</i> isolates and the 38 non-Chinese <i>B. canis</i> strains. In the columns, the following data for isolates are indicated: Strain: laboratory identifier of isolate in which the DNA extraction was performed, No. genotype numbering, Place/Year: country and year of isolation (when known), MLVA-8: genotype numbers associated with the genotypes corresponding to each isolates in the database.</p

<i>Brucella canis</i> isolates and characterization using different molecular typing methods.

a<p>: <i>B.canis</i> specific primers only;</p>b<p>: Characterization of <i>B. canis</i> BMEI1435 gene deletion (related to the genome of <i>B. melitensis</i> 16M, AE008917).</p>c<p>: The mutation of <i>omp</i>25 gene at position 545 (SNP position related to the genome of <i>B. abortus</i> 9-941, GenBank ID: AE017223).</p>1<p>: isolated from dog.</p>2<p>: isolated from human.</p

Hunter-Gaston Diversity Index (HGDI) for the 67 <i>Brucella canis</i> isolates.

a<p>: Hunter and Gaston index.</p>b<p>: Precision of the diversity index, expressed as 95% upper and lower boundaries.</p