Oral Presentation The 3rd Prato Conference on the Pathogenesis of Bacterial Diseases of Animals 2014

Weakly hemolytic Brachyspira hyodysenteriae strains in pigs (#39)

Maxime Mahu 1 , Nele De Pauw 1 , Lien Vande Maele 1 , Marc Verlinden 1 , Filip Boyen 1 , Richard Ducatelle 1 , Freddy Haesebrouck 1 , An Martel 1 , Frank Pasmans 1
  1. Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium

Infections with Brachyspira species in swine occur in most swine-rearing countries and can result in substantial economic losses. Of all swine-associated Brachyspira species infections, classical swine dysentery, caused by Brachyspira hyodysenteriae, results in the most severe clinical symptoms (1). The strongly hemolytic species B. hyodysenteriae, “B. suanatina” and “B. hampsonii” are considered to be more pathogenic for pigs than the weakly hemolytic species B. intermedia, B. innocens and B. murdochii (2, 3). This led to the assumption that the degree of hemolysis may be linked with the virulence of a species.

This study aims to compare the hemolytic capacity of different B. hyodysenteriae strains, to relate the degree of hemolysis to the pathogenic potential and to identify the underlying molecular differences. Hemolysis of ten B. hyodysenteriae strains was quantified in an in vitro assay for hemolytic capacity in which supernatant of each strain was incubated with a 10% porcine red blood cell suspension where after absorption was measured (4). Complete sequences of the hemolysis associated genes hlyA, tlyA, tlyB and tlyC were determined for all B. hyodysenteriae strains. The virulence of a weakly and a strongly hemolytic B. hyodysenteriae strain were compared in experimentally infected pigs (5).

Hemolysis of the B. hyodysenteriae strains varied from near absence to pronounced hemolysis. One weakly hemolytic B. hyodysenteriae strain showed amino acid substitutions in tlyA and tlyB and, in contrast to a strongly hemolytic strain, proved to be non-pathogenic in experimentally infected swine.

This study points out that the degree of hemolysis and the virulence of B.hyodysenteriae strains can vary and that weakly hemolytic B. hyodysenteriae strains can be found in fecal samples of swine. The appearance of weakly hemolytic, avirulent strains of B. hyodysenteriae is problematic for swine industry since they may affect herd dysentery status, thus compromising trading opportunities.

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  2. Råsbäck, T., Jansson, D. S., Johansson, K., & Fellström, C., 2007. A novel enteropathogenic, strongly haemolytic spirochaete isolated from pig and mallard, provisionally designated “ Brachyspira suanatina ” sp. nov., Environ Microbiol 9(4), 983–991.
  3. 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(5), 903–10.
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  5. Jacobson, M., Fellström, C., Lindberg, R., Wallgren, P., Jensen-Waern, M., 2004. Experimental swine dysentery: comparison between infection models. J Med Microbiol 53(4), 273–280.