Phenotypic and genotypic profiles of human, canine, and porcine spirochetes associated with colonic spirochetosis correlates with in vivo brush border attachment.

A group of phenotypically and genotypically distinct weakly beta-hemolytic intestinal spirochetes (WBHIS) have been associated with a diarrheal disease of humans, dogs and swine, designated colonic spirochetosis (CS). Because attachment of spirochetes to the brush border of colonic enterocytes is a consistent feature of CS, it may represent an important virulence mechanism. In this study, pure cultures of WBHIS obtained from humans, dogs, and swine with clinical signs or lesions of CS were compared with Serpulina innocens using biochemical, genotypic and an in vivo brush border attachment assay CS-associated WBHIS did not form genotypic and an in vivo brush border attachment assay CS-associated WBHIS did not form indole, but hydrolyzed hippurate. Analysis of genomic DNA using arbitrarily primed-PCR (AP-PCR) revealed that the CS-associated WBHIS had a closely related pattern which was distinctly different from that of S. innocens. For in vivo brush border attachment assays, one-day old chicks were inoculated by crop gavage with either sterile trypticase soy broth or broth containing either S. innocens or CS-associated WBHIS. On day 7 post-inoculation, the ceca of sham-inoculated control chicks and S. innocens-inoculated chicks had tall columnar enterocytes without spirochetes, and no spirochetes were isolated by culture on selective medium. Focal to segmental attachment of spirochetes to the brush border of superficial enterocytes was present in the ceca of chicks inoculated with WBHIS, and weakly beta-hemolytic spirochetes with effacement of the microvillous brush border of colonic enterocytes. Complete agreement between hippurate hydrolysis, specific- and AP-PCR assays and in vivo brush border attachment studies confirms the enteropathogencity of CS-associated WBHIS.