Molecular characteristics of Brucella isolates in Shanghai, 2007–2020

  Objective  To investigate the molecular characteristics of Brucella isolates in Shanghai from 2007 to 2020, understand the genotyping and clustering of the strains, and provide evidence for the prevention and treatment of brucellosis.

  Methods  A total of 20 clinical Brucella strains were isolated in Shanghai from 2007 to 2020. The strains were preliminarily identified by the biochemical method and AMOS-PCR. The multilocus sequence typing (MLST), multilocus variable number tandem repeat analysis (MLVA) and whole genome sequencing (WGS) based single nucleotide polymorphism (SNP) analysis were used to for molecular typing, and cluster analysis was performed with reference strains.

  Results  By MLST, the 20 isolates were identified as Brucella melitensis, belonging to sequence types (ST) 8. They were typed into 4 genotypes by MLVA-8 and 17 genotypes by MLVA-16, while locus of panel 2B showed polymorphism. WGS-based SNP analysis demonstrated that all the clinical strains were in cluster of B. melitensis, and some of which shared close phylogenetic relationship.

  Conclusion  The strains isolated from human brucellosis cases in Shanghai from 2007 to 2020 were mainly ST8 B. melitensis. Molecular typing can provide evidence for tracing of human brucellosis in Shanghai.