Abstract
A novel Brachyspira emerged in 2009 and has since become a production-limiting pathogen of pigs in North America. The name “ Brachyspira hampsonii” has been proposed for this novel taxon. “ Brachyspira hampsonii” is divided into two phylogenetically distinct clades based on the sequence of the NADH-oxidase ( nox) gene, although the clinical disease associated with clades I and II is indistinguishable and phenotypic characteristics that discriminate the clades have not been determined. The objectives of the current study were to enhance the description of the provisional species “ B. hampsonii” with biochemical profiles and morphometric data from isolates affecting Canadian swine and to investigate potentially diagnostically informative characteristics for this emerging pathogen. Biochemical profiles of isolates from different commercial swine barns in Western Canada showed that biochemical profiles were insufficient to distinguish “ B. hampsonii” clades I and II from each other or from other pathogenic Brachyspira. Hippurate hydrolysis, previously reported as uniformly negative in “ B. hampsonii,” was variable among Canadian isolates. Spirochete dimensions and flagella numbers for “ B. hampsonii” overlapped with other Brachyspira species. Taken together, these results indicate that nox gene sequencing remains a preferred method for identification and discrimination of “ B. hampsonii” from other pig-associated Brachyspira spp.
Highlights
The genus Brachyspira consists of Gram-negative, motile, β-haemolytic, aerotolerant spirochaetes infecting the gastrointestinal tracts of wild and domestic animals, as well as humans
The number of isolates included in the study from either clade reflects higher isolation rates of clade II isolates from clinical samples submitted to our laboratory, which to our knowledge was the only laboratory performing clade level identification of “B. hampsonii” in Western Canada during the period of study
Indole production was negative for all isolates as expected, hippurate hydrolysis activity was inconsistent among isolates in both clades (Table 1)
Summary
The genus Brachyspira consists of Gram-negative, motile, β-haemolytic, aerotolerant spirochaetes infecting the gastrointestinal tracts of wild and domestic animals, as well as humans. Brachyspira hyodysenteriae is the causative agent of swine dysentery (Harris et al 1972), whereas Brachyspira pilosicoli infection is associated with spirochaetal colitis (Trott et al 1996). “Brachyspira suanatina”, originally isolated from mallard ducks, has been shown to cause dysentery-like disease in experimentally inoculated pigs (Råsbäck et al 2007). Other species (Brachyspira intermedia, Brachyspira innocens, and Brachyspira murdochii) detected in pigs are non-pathogenic or have been reported to cause mild catarrhal colitis under experimental conditions (Stanton et al 1997; Jensen et al 2010). Phylogenetic analysis of the NADH-oxidase (nox), 16S rRNA, and 23S rRNA genes revealed two distinct clades within the taxon (Chander et al 2012; Burrough et al 2013; Rubin et al 2013b). The clinical disease associated with clades I and II is indistinguishable (Rubin et al 2013a; Costa et al 2014), the phenotypic properties distinguishing them have not been established
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