Isolation of Serpulina pilosicoli from rectal biopsy specimens showing evidence of intestinal spirochetosis.

Histologic evidence of intestinal spirochetosis (IS) was found in 22 of 41 (53.7%) rectal biopsy specimens from homosexual men attending a sexually transmitted diseases clinic. Serpulina pilosicoli was cultured from 11 of the IS-positive biopsy specimens (50%) and from 2 specimens (10.5%) in which spirochetes were not observed. The association between seeing spirochetes in biopsy specimens and isolating S. pilosicoli was statistically significant, clearly indicating that this spirochete is the agent of IS.