Motility and chemotaxis in Serpulina hyodysenteriae

Chemotactic- or motility-regulated mucus association appears to be the predominant mechanism of mucosal association by the causative agent of swine dysentery, Serpulina hyodysenteriae. In the present study, a modification of the Adler capillary assay was used to evaluate the chemotactic responses of S. hyodysenteriae to a variety of potential stimuli. First, however, it became necessary to study factors that influenced motility of the spirochete in vitro, since standard cultivation methods produced motility inferior to that observed for in vivo grown cells. A number of factors were found to influence S. hyodysenteriae motility, but of these growth medium and growth phase appeared to be the most important. The type and even batch of culture medium also were found to have a significant influence on S. hyodysenteriae motility. Optimal motility and chemotaxis for S. hyodysenteriae was observed when the cells were harvested in mid- to late-log phase, and in vivo-like motility could be induced by suspending the cells in physiologic saline. S. hyodysenteriae was strongly attracted to hog gastric mucin, certain concentrations of blood, L-fucose, L-serine and other compounds. Selected sugars and other amino acids did not serve as chemoattractants for S. hyodysenteriae. The chemotactic response of S. hyodysenteriae toward L-fucose and L-serine, constituents of mucin, may be important factors in the affinity of the spirochete for the mucus in the intestinal tract of swine.