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Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties.

ABSTRACT: Brachyspira (B.) hyodysenteriae is widespread globally, and can cause mucohaemorrhagic colitis (swine dysentery, SD) with severe economic impact in infected herds. Typical strains of B. hyodysenteriae are strongly haemolytic on blood agar, and the haemolytic activity is believed to contribute to virulence in vivo. However, recently there have been reports of atypical weakly haemolytic isolates of B. hyodysenteriae (whBh). In this study, 34 European whBh and 82 strongly haemolytic isolates were subjected to comparative genomic analysis. A phylogenetic tree constructed using core single nucleotide polymorphisms showed that the whBh formed a distinct sub-clade. All eight genes previously associated with haemolysis in B. hyodysenteriae were present in the whBh. No consistent patterns of amino acid substitutions for all whBh were found in these genes. In contrast, a genome region containing six coding sequences (CDSs) had consistent nucleotide sequence differences between strongly and whBh isolates. Two CDSs were predicted to encode ABC transporter proteins, and a TolC family protein, which may have a role in the export of haemolysins from B. hyodysenteriae. Another difference in this region was the presence of three CDSs in whBh that are pseudogenes in strongly haemolytic isolates. One of the intact CDSs from whBh encoded a predicted PadR-like transcriptional repressor that may play a role in repression of haemolysis functions. In summary, a sub-clade of whBh isolates has emerged in Europe, and several genomic differences, that potentially explain the weakly haemolytic phenotype, were identified. These markers may provide targets for discriminatory molecular tests needed in SD surveillance.

SUBMITTER: Card RM

PROVIDER: S-EPMC6407217 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties.

Card Roderick M RM La Tom T Burrough Eric R ER Ellis Richard J RJ Nunez-Garcia Javier J Thomson Jill R JR Mahu Maxime M Phillips Nyree D ND Hampson David J DJ Rohde Judith J Tucker Alexander W AW

Veterinary research 20190307 1

Brachyspira (B.) hyodysenteriae is widespread globally, and can cause mucohaemorrhagic colitis (swine dysentery, SD) with severe economic impact in infected herds. Typical strains of B. hyodysenteriae are strongly haemolytic on blood agar, and the haemolytic activity is believed to contribute to virulence in vivo. However, recently there have been reports of atypical weakly haemolytic isolates of B. hyodysenteriae (whBh). In this study, 34 European whBh and 82 strongly haemolytic isolates were s ...[more]

PMID: 30845993

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Project description:BACKGROUND:Swine dysentery (SD) is a diarrheal disease in fattening pigs that is caused by the strongly hemolytic species Brachyspira (B.) hyodysenteriae, B. hampsonii and B. suanatina. As weakly hemolytic Brachyspira spp. are considered less virulent or even non-pathogenic, the hemolysin is regarded as an important factor in the pathogenesis of SD. Four hemolysin genes (tlyA, tlyB, tlyC, and hlyA) and four putative hemolysin genes (hemolysin, hemolysin activation protein, hemolysin III, and hemolysin channel protein) have been reported, but their role in strong hemolysis is not entirely clear. Our study aimed to assess the transcriptional activity of eight (putative) hemolysin genes in a strongly hemolytic (B204) and a weakly hemolytic (G423) B. hyodysenteriae strain during non-hemolytic and hemolytic growth stages. RESULTS:Strongly and weakly hemolytic B. hyodysenteriae strains caused hemolysis on blood agar at different growth stages, namely during log phase (B204) and stationary/death phase (G423). During the lag, early log, late log (stationary phase in G423) and death phase (time points 1-4) strains differed in their hemolysin gene transcription patterns. At time point 1, transcription of the putative hemolysin gene was higher in B204 than in G423. At time point 2, tlyA and tlyC were upregulated in B204 during hemolysis. TlyB and hlyA were upregulated in both strains at all time points, but higher transcription rates were observed in the weakly hemolytic strain G423. The transcription activity of the hemolysin channel protein gene was quite similar in both strains, whereas the hemolysin activation protein gene was upregulated in the non-hemolytic stage of B204 at time point 4. Sequence analysis revealed deletions, insertions and single nucleotide polymorphisms in the G423 hlyA promoter, although without altering the transcription activity of this gene. CONCLUSION:Our data indicate a combined activity of TlyA and TlyC as the most probable underlying mechanism of strong hemolysis in B. hyodysenteriae. Further studies should verify if the expression of tlyA is upregulated by the putative hemolysin gene. Depending on their immunogenic potential TlyA and TlyC may serve as possible vaccine candidates, especially since vaccines for an effective control of swine dysentery are currently not available.

Dataset Information

Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties.

Publications

Weakly haemolytic variants of Brachyspira hyodysenteriae newly emerged in Europe belong to a distinct subclade with unique genetic properties.

Similar Datasets

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