In the final tally there were assays for eight branches of the phylogeny, with assays specific to the following prominent isolates/clades and related isolates: B. abortus 2308, B. abortus 2308 + S19, B. melitensis 16 M, B. melitensis biovar 1, and
selleck compound B. suis 1330. From our diverse isolate collection we had the following distribution of calls for the branches, with the most derived call taking precedence over more ancestral calls: A = 1, B = 23, C = 8, D = 22, E = 7, F = 0, G = 15, H = 91, I = 33, J = 17, no derived call (all isolates not in species B. abortus, B. melitensis, or B. suis/ canis) = 25, no call for any assay = 7, ancestral within B. abortus = 12, ancestral within B. melitensis = 68, ancestral within B. suis = 11. Discussion Our assays show clear distinctions within and among B. abortus B. melitensis, and B. suis. Our CUMA assays targeted clade-specific SNPs that can be incorporated into most other genotyping assays such as TaqMan learn more Real-time PCR for increased
sensitivity [18, 19]. We have identified several important targets that should prove useful for clinical, epidemiological, and forensic purposes. For example, the assays targeting branches A, D, and I are specific to isolates closely related to B. abortus 2308 and B. abortus 9–941, and Selleck GSK2245840 B. suis 1330, respectively. The assays for F and G target the same branch and identify B. melitensis 16 M and closely related isolates. Isolates from B. abortus 2308 and 9–941, B. suis 1330, and B. melitensis 16 M are from common, genetically monomorphic clades of Brucella and the SNP assays developed here are a
reliable and useful way of identifying these four common groups. Branch E is particularly interesting in terms of Brucella taxonomy. The clade that this branch defines includes isolates from B. abortus biovars 1, 2, and 4. Potential issues with biovar and phylogenetic correspondence from in B. abortus have been noted previously . Upon closer evaluation of the whole genomes used in our analyses, the apparent paraphyly within B. abortus biovar 1, since isolates from biovar 2 are within the biovar 1 clade, does not hold true when all the genomes are included. However, CUMA assays indicate that at least four isolates from other B. abortus biovars (3 of biovar 4, 1 of biovar 2) fall onto the B/C branch. This would suggest that either biovar 1 is paraphyletic or there have been issues with biovar determination. SNP-based approaches also enable assessment of errors in genome sequences. Whole genome comparisons of the region associated with SNP10621, which were intended to target branch J in B. suis/ B. canis, also share a SNP allele with B. abortus 9–941. Taken at face value, this would suggest homoplasy at this locus. Yet, in our CUMA assays B. abortus 9–941 did not group with B. suis, likely indicating sequencing error.