Characterization and recognition of Brachyspira hampsonii sp. nov., a novel intestinal spirochete that is pathogenic to pigs.

Journal of clinical microbiology

PubMedID: 27629903

Mirajkar NS, Phillips ND, La T, Hampson DJ, Gebhart CJ. Characterization and recognition of Brachyspira hampsonii sp. nov., a novel intestinal spirochete that is pathogenic to pigs. J Clin Microbiol. 2016;.
Swine dysentery (SD) is a mucohemorhagic colitis of swine classically caused by infection with the intestinal spirochete Brachyspira hyodysenteriae. Since around 2007, cases of SD have occurred in North America associated with a different strongly beta-hemolytic spirochete that has been molecularly and phenotypically characterized and provisionally named "Brachyspira hampsonii". Despite increasing international interest, "B. hampsonii" is currently not recognized as a valid species. To support its recognition, we sequenced the genomes of strains NSH-16, NSH-24 and P280/1, representing "B. hampsonii" genetic groups I, II and III, respectively, and compared them with genomes of other valid Brachyspira species. The draft genome of strain NSH-16 has a DNA G+C content of 27. 4% and an approximate size of 3. 2 Mb. Genomic indices including digital DNA-DNA hybridization (dDDH), Average Nucleotide Identity (ANI) and Average Amino Acid Identity (AAI) clearly differentiated "B. hampsonii" from other recognized Brachyspira species. Although discriminated genotypically, the three genetic groups remain phenotypically similar. By electron microscopy, cells of different strains of "B. hampsonii" measure 5-10 µm x 0. 28-0. 34 µm, with one or two flat curves, and have 10 to 14 periplasmic flagella inserted at each cell end. Using a comprehensive evaluation of genotypic (gene comparisons and multi-locus sequence typing and analysis), genomic (dDDH, ANI and AAI) and phenotypic (hemolysis, biochemical profiles, protein spectra, antibiogram and pathogenicity) properties, we classify Brachyspira hampsonii sp. nov. as a unique species with genetically diverse yet phenotypically similar 'genomovars' (I, II and III). We designate the type strain as NSH-16(T) (=ATCC® BAA-2463™ = NCTC 13792).