Genetic diversity of Brucella ovis isolates from Rio Grande do Sul, Brazil, by MLVA16

Abstract

BackgroundOvine epididymitis is predominantly associated with Brucella ovis infection. Molecular characterization of Brucella spp. achieved by multi-locus variable number of tandem repeats (VNTR) analyses (MLVA) have proved to be a powerful tool for epidemiological trace-back studies. Thus, the aim of this study was to evaluate the genetic diversity of Brucella ovis isolates from Rio Grande do Sul State, Brazil, by MLVA16.FindingsMLVA16 genotyping identified thirteen distinct genotypes and a Hunter-Gaston diversity index of 0.989 among the fourteen B. ovis genotyped strains. All B. ovis MLVA16 genotypes observed in the present study represented non-previously described profiles. Analyses of the eight conserved loci included in panel 1 (MLVA8) showed three different genotypes, two new and one already described for B. ovis isolates. Among ten B. ovis isolates from same herd only two strains had identical pattern, whereas the four isolates with no epidemiologic information exhibited a single MLVA16 pattern each. Analysis of minimal spanning tree, constructed using the fourteen B. ovis strains typed in this study together with all nineteen B. ovis MLVA16 genotypes available in the MLVAbank 2014, revealed the existence of two clearly distinct major clonal complexes.ConclusionsIn conclusion, the results of the present study showed a high genetic diversity among B. ovis field isolates from Rio Grande do Sul State, Brazil, by MLVA16.

Pathogenic potential of Brucella ovis field isolates with different genotypic profile and protection provided by the vaccine strain B. ovis ΔabcBA against B. ovis field isolates in mice

“…For instance, the vaccine strain B. abortus S19, isolated in 1923 from the milk of a Jersey cow (Buck 1930), that after being accidentally left out at room temperature for one year spontaneously developed an attenuated phenotype (Graves 1943). Importantly, there were no previous studies comparing the pathogenicity of B. ovis strains with different genotypes based on MLVA-16 (Dorneles et al 2014).…”

“…All seven B. ovis strains included in this study were directly isolated from the semen of naturally infected rams (Dorneles et al 2014), indicating that these rams likely had clinical changes and were sources of infection to other sheep within their herds (Burgess 1982). Although there is no information regarding clinical signs associated with these isolates, MLVA16 demonstrated different genotypes (Dorneles et al 2014). Therefore, in order to assess possible differences in pathogenic potential of these strains, we used the mouse, which has been extensively employed as an infection model for Brucella spp.…”

“…B. ovis strains included in this study were isolated directly from the natural host (Dorneles et al 2014), where the bacteria face harsh intracellular conditions including exposure to reactive oxygen species, low pH, and low nutrient levels. Brucella spp.…”

“…Bacterial strains. As detailed in Table 1, this study included seven field Brucella ovis strains isolated from semen of naturally infected rams, which have been previously genotypically characterized by MLVA-16 (Dorneles et al 2014), the reference wild-type strain B. ovis ATCC 25840, and the candidate vaccine strain B. ovis ΔabcBA (Silva et al 2011b(Silva et al , 2015a(Silva et al , 2015b. Bacteria were grown on the tryptic soy agar (TSA) plates supplemented with 1% hemoglobin, for 3 days at 37°C with 5% CO 2 .…”

“…(Whatmore 2009). The analysis of fourteen B. ovis Brazilian field isolates demonstrated some degree of genetic diversity (Dorneles et al 2014). Considering the molecular differences identified by MLVA-16 among B. ovis field isolates, the aim of this study was to characterize field isolates of B. ovis in a murine model of infection and to evaluate the efficiency of the B. ovis ΔabcBA vaccine strain to protect mice challenged with B. ovis field isolates.…”