Genotyping of human Brucella melitensis strains isolated in Shanxi province by MLVA-2B typing and rpoB typing

Abstract

Objective To analyze the genotypes of Brucella melitensis strains isolated in Shanxi province by using multiple-locus variable-number tandem-repeat 2B typing (MLVA-2B) and rpoB typing. Methods Brucella strains were isolated by culturing the blood samples collected from patients with brucellosis in Shanxi province from 2014 to 2015 and then were identified with conventional methods. MLVA panel 2 (eight loci)was used to identify the genotypes of the Brucella melitensis strains, and the results were further analyzed by cluster analysis. The rpoB gene was molecularly characterized by PCR amplification and DNA sequencing in those strains. The rpoB nucleotide sequences of all Brucella strains were compared with the published rpoB gene sequence of the Brucella melitensis strain 16M to reveal specific nucleotide variations. Results A total of 41 Brucella strains were isolated in 2014 and 2015 and all of them belonged to Brucella melitensis biovar 3. Those strains were divided into five groups and thirty-one MLVA types based on MLVA panel 2B with a genetic similarity ranging from 64.78% to 100%. Four mutation sites in rpoB gene were investigated in the 41 Brucella strains and based on that analysis, those strains were grouped as rpoB-2 (629-GTG/985-GTC/1309-CTA, 95.12%) and rpoB-2 variant (629-GTG/1309-CTA, 4.88%). Conclusion MLVA genotyping was significant for analyzing the sources, epidemics and outbreaks of brucellosis. Analyzing the panel 2B loci was a simple and efficient way for genotyping the Brucella melitensis strains isolated in Shanxi province. The 41 strains belonged to two genotypes on the basis of rpoB typing, including 39 strains of rpoB-2 genotype and 2 strains of a new genotype rpoB-2 variant. There might be a correlation between MLVA and rpoB genotyping. Key words: Brucella; Multiple-locus variable-number tandem-repeat analysis; rpoB gene