Comparative virulence of clinicalBrachyspiraspp. isolates in inoculated pigs

Abstract

Classical swine dysentery is associated with the presence of the strongly beta-hemolytic Brachyspira hyodysenteriae. However, multiple Brachyspira spp. can colonize the porcine colon. Since 2008, several Brachyspira spp. not identified as B. hyodysenteriae by genotypic and/or phenotypic methods have been isolated from the feces of pigs with clinical disease typical of swine dysentery. In the current study, 8 clinical isolates, including 5 strongly beta-hemolytic and 3 weakly beta-hemolytic Brachyspira strains, and a reference strain of B. hyodysenteriae (B204) were inoculated into pigs (n = 6 per isolate) to compare pathogenic potential following oral inoculation. Results revealed that strongly beta-hemolytic isolates induced significantly greater typhlocolitis than those that are weakly beta-hemolytic, regardless of the genetic identification of the isolate, and that strongly beta-hemolytic isolates identified as "Brachyspira sp. SASK30446" and Brachyspira intermedia by polymerase chain reaction (PCR) produced lesions similar to those caused by B. hyodysenteriae. The results suggest that phenotypic culture characteristics of Brachyspira spp. may be a more sensitive indicator of potential to induce dysentery-like disease in pigs than molecular identification alone based on currently available PCR assays. Additionally, culture of mucosal scrapings obtained at necropsy was more sensitive than direct PCR on the same samples for detection of Brachyspira spp.

Identification of weakly haemolytic Brachyspira isolates recovered from pigs with diarrhoea in Spain and Portugal and comparison with results from other countries

“…Consequently other identification methods have been developed based on the sequence of conserved genes, notably those encoding 16S rRNA, 23S rRNA and NADH oxidase (nox). Analysis of nox sequences has emerged as a robust method for identification of Brachyspiraspecies as the gene is relatively conserved but also shows speciesspecific variation (Atyeo et al, 1999;Burrough et al, 2012;Chander et al, 2012;Rubin et al, 2013). A more discriminatory multilocus sequence typing (MLST) scheme analyzing the sequence of seven genes encoding "housekeeping" enzymes has been described for identification and typing of Brachyspira isolates (Råsbäck et al, 2007b), but it is laborious and has not been widely used apart from analysis of B. hyodysenteriae (La et al, 2009;Osorio et al, 2012) and other indole-positive species (Phillips et al, 2010).…”

Comparison of culture, polymerase chain reaction, and fluorescent in situ hybridization for detection of Brachyspira hyodysenteriae and “Brachyspira hampsonii” in pig feces

“…The "B. hampsonii " clade II strain (EB107) was originally recovered from a clinical case of SD in 2011 and has been previously used in multiple pig inoculation experiments. 3,14 The B. hyodysenteriae strain (B204) was originally recovered from a clinical case of SD in 1972. The B. murdochii (KC63) and B. pilosicoli (P43/6/78) strains were obtained from a clinical case in 2008 and the American Type Culture Collection, respectively.…”

“…8 However, a recently proposed novel Brachyspira species, "Brachyspira hampsonii ", 5 has been isolated from pigs with mucohemorrhagic diarrhea, and experimental infection with "B. hampsonii " strains has consistently resulted in clinical disease and gross lesions that are similar to, if not indistinguishable from, B. hyodysenteriae infection. 3,12,14 A definitive diagnosis of SD is commonly based on the isolation of strongly beta-hemolytic, ring phenomenon-positive spirochetes from culture of mucohemorrhagic feces or colonic tissue and/or by species-specific polymerase chain reaction (PCR) assays run on extracts of such samples. 4 While Brachyspira culture using selective agars is a highly sensitive assay, it can be technically challenging, time consuming, typically requires speciation using PCR following isolation, and often requires 6 days or longer to complete, which can result in a delay in disease diagnosis.…”

Hibridização in situ fluorescente para diagnóstico de Brachyspira hyodysenteriae e B. pilosicoli em suínos

“…Esse gênero possui sabidamente três espécies patogêni-cas; Brachyspira hyodysenteriae, B. pilosicoli e B. hampsonii (Hampson & Trott 2006, Harris et al 2006, Burrough et al 2012. Outras espécies não patogênicas de Brachyspira (B. innocens e B. murdochii) são habitantes normais do intestino grosso de suínos, o que pode dificultar o diagnóstico.…”

“…Outras espécies não patogênicas de Brachyspira (B. innocens e B. murdochii) são habitantes normais do intestino grosso de suínos, o que pode dificultar o diagnóstico. O quadro clinico de diarreia muco hemorrágica, altas taxas de mortalidade, e lesões graves de enterite muco hemorrágica associada a áreas de necrose são indistinguíveis entre casos de infecção por B. hyodysenteriae e B. hampsonii (Burrough et al 2012, Rubin et al 2013, Wilberts et al 2014, mas B. hampsonii nunca foi diagnosticada no Brasil. Já a infecção por B. pilosicoli causa diarreia pastosa acinzentada com comprometimento do ganho de peso de animais recentemente alojados na fase de recria.…”