Analysis of pathogens and genetic characteristics of Brucella canis

Abstract

Objective To analyze the etiology and genetic characteristics of canine brucellosis in a relatively closed population. Methods Canine brucellosis was detected in an experimental animal breeding base. The research methods consisted of serological testing [tube agglutination test (TAT)], strain identification (biochemical and phage testing), histopathological examination of tissue (liver, spleen and testis) specimens of dog, genetic characteristics analyzing of the strains [16S rRNA gene sequencing, real-time PCR (RT-PCR), multilocus sequence typing (MLST), pulse field gel electrophoresis analysis (PFGE), and multilocus variable number tandem repeat analysis (MLVA) and IS711 southern hybridization]. Results Totally 51.25% (41/80) of serum specimen from Beagle dogs was positive with antibody titer above 1 ∶ 50. The Brucella DNA of 80 blood specimen was positive by RT-PCR detection. The lesion tissues and pathogenic bacteria like cells were found in the liver, spleen and testis. Totally 10 isolates, which were cultured from blood specimen were confirmed as Brucella canis by biochemistry and phage testing. Sequence analysis of 16S rRNA gene for the 10 isolates was consistent with that of Brucella in the database. The results of the three genotyping methods for the 10 strains were identical by MLST, PFGE and IS711 southern hybridization. The 10 isolates were clustered into two different MLVA genotypes. Conclusions It is identified as a canine brucellosis outbreak based on the databases of serology, bacteriology, 16S rRNA gene sequence analysis, histopathology and genotyping by PFGE, MLST and MLVA. The ten Brucella canis isolates seem to origin from a same clone, and evolve into two stable and heritable MLVA genotypes in the natural environment. Key words: Brucella canis; Genes; Analysis