Identification of Brucella mutants by multiple locus variable-number tandem repeat analysis assay

ObjectiveTo classify Brucella variants by using multiple locus variable-number tandem repeat analysis (MLVA) assay.

MethodsThirty nine clinical Brucella isolates were identified as Brucella variants by biological methods. They were classified again by MLVA assay.

ResultsThirty nine strains Brucella isolates agglutinated with rough type serum R and could be also cleaved by BK2 phage. But Wb and Tb phages were not cleaved. The biological types were uncertain. 9 strains could agglutinate weakly with serum A and M. 2 strains could agglutinate weakly with serum M. The other 28 strains did not agglutinate with serum A and M. The 39 strains were identified as Brucella variants by biological detection methods. The MLVA assay including 16 tandem repeats loci were used to analyze the 39 Brucella isolates and 17 Brucella reference strains (6 species and types). Cluster analysis showed that in the 39 strains of Brucella variants, 2 strains were similar to Brucella abortus biovar 2 or 4, and 37 strains were similar to Brucella melitensis biovar 3.

ConclusionThe conventional biological identification methods combined with MLVA assay seems to be suitable for further classification of Brucella strains, especially for Brucella variant.