Proposed pathogenic mechanism for the diarrhea associated with human intestinal spirochetes.

Spirochetes resembling Brachyspira aalborgi were found in the feces and rectal biopsies of a patient with persistent diarrhea. Although the organism failed to grow on bacteriologic media, it was found attached to the surfaces of the epithelial cells on the rectal lumen. Blunting and destruction of the cellular microvilli was evident. These induced pathologic cell surface changes, together with the presence of intracellular bacteria in the cells of the rectal colon, suggest a pathogenic mechanism for the persistent diarrhea often associated with this condition. Both the spirochetosis and clinical symptoms disappeared on treatment with metronidazole.