Association of Treponema hyodysenteriae with porcine intestinal mucosa.

The association of Treponema hyodysenteriae with porcine caecal and colonic mucosal surfaces was studied by electron microscopy after orogastric inoculation of pigs with pure cultures. Examination of caecal and colonic mucosa from infected and control animals revealed that large numbers of the spirochaete were associated only with intestinal mucosal surfaces of infected animals. Further examination of the intestinal mucosa from infected pigs showed that T. hyodysenteriae colonized two sites preferentially: the mucus-filled crypts of Lieberkühn and the mucus gel covering the epithelium. Furthermore, no evidence of either specific or nonspecific adhesion to the epithelium proper was found, suggesting that penetration of, or trapping in the mucus gel may be the predominant mechanism of mucosal association by T. hyodysenteriae. Moreover, T. hyodysenteriae was also observed to be highly motile in intestinal mucus, moving faster than any other organism present, and this 'high speed' motility appeared to facilitate penetration into the mucosa. The pattern of motility observed was also highly suggestive of chemotaxis, and this was subsequently confirmed using an in vitro assay to porcine mucus material. It is suggested, therefore, that motility and chemotaxis are important factors/mechanisms in the association and colonization of porcine intestinal mucosa by T. hyodysenteriae.