Molecular typing for epidemiological evaluation of Brucella abortus and Brucella canis isolated in Korea.

To investigate genotype relationships among regional groups of Brucella isolates, variable-number tandem-repeat (VNTR) analysis was conducted according to previously reported methods. Field strains of Brucella abortus and Brucella canis were isolated from 9 provinces in the Republic of Korea during the years 1996-2006 and each of the isolates was classified by eight loci of HOOF-Prints. On the basis of the alleles, the 33 B. abortus and 21 B. canis field strains were divided into 22 and 18 distinct genotypes, respectively. Phylogenetic cluster analysis of Brucella isolates could be discriminated with geographical region in the Republic of Korea. Simpson's diversity index values of B. abortus and B. canis isolates ranged from 0 to 0.85. The stability of each locus was determined with in vivo and in vitro experiments. After twenty passages in blood agar, the VNTR numbers of loci 1 and 7 in B. abortus isolates and loci 5, 7, and 8 in B. canis isolates changed. The same change of the VNTR numbers at loci 1 and 7 was observed with B. abortus RB51 strains isolated from vaccinated cattle for the in vivo experiment. Although B. canis and B. abortus isolates were discriminated to herd levels by the HOOF-Prints, this method needs further improvement for the high variable locus. This study represents the first epidemiological data of molecular typing of B. abortus and B. canis reported in Korea.