Since 2008, there have been increasing reports of disease resembling SD from which strongly beta-hemolytic spirochetes other than B. hyodysenteriae were isolated by culture. These strongly beta-hemolytic spirochetes have been extensively studied and their pathogenic potential has been confirmed experimentally where disease resembling classic SD was observed following inoculation of pigs with several of these strains (Burrough et al., 2012). Molecular and biochemical analysis of these strongly beta-hemolytic isolates suggests they are related and that a novel species has emerged in the United States with the proposed name “Brachyspira hampsonii” (Chander et al., 2012).
This new species is divided into two clades, “B. hampsonii” clade I and clade II. Analysis of the nox gene sequences of the type strains of these two clades further reveals that clade I isolates are analogous to those previously identified at the ISU VDL as strongly beta-hemolytic Brachyspira intermedia, and that clade II isolates are analogous to those reported as “Brachyspira sp. SASK30446 (novel)”.
In keeping with current nomenclature, these isolates will now be reported as “B. hampsonii” on diagnostic reports from the ISU VDL, and the identification of “B. hampsonii” from clinical specimens should be interpreted as compatible with a diagnosis of SD. Routine identification of Brachyspira spp. will be based upon nox gene sequencing at a fee of $50 from primary cultures, and custom sequence diagrams can be requested as an additional service.
Burrough, E.R., Strait, E.L., Kinyon, J.M., Bower, L.P., Madson, D.M., Wilberts, B.L., Schwartz, K.J., Frana, T.S., Songer, J.G., 2012, Comparative virulence of clinical Brachyspira spp. isolates in inoculated pigs. J Vet Diagn Invest 24, 1025-1034.
Chander, Y., Primus, A., Oliveira, S., Gebhart, C.J., 2012, Phenotypic and molecular characterization of a novel strongly hemolytic Brachyspira species, provisionally designated "Brachyspira hampsonii". J Vet Diagn Invest 24, 903-910.