Species involved: Brachyspira species (Br. aalborgi, Br. pilosicoli, others)
The organisms may have surface receptors that bind to microvilli on colonic surface epithelium.
Risk factors:
(1) living in a developing country
(2) male gender
(3) male homosexuality
(4) immune deficiency, including HIV
(5) colonic stasis
Clinical features:
(1) often asymptomatic and identified as an incidental finding
(2) watery diarrhea
(3) possible sepsis
Pathologic findings:
(1) There is a diffuse growth of spirochetes along the mucosal surface of the large intestine appearing as a "diffuse bluish fringe".
(2) The organisms can be demonstrated on silver stain (Warthin Starry, other) or with immunostains using antibodies to Treponema pallidum
Microbiologic demonstration:
(1) culture (but Br. aalborgi is fastidious and difficult to isolate)
(2) nucleic acid extraction from stool followed by PCR (using genes for 16S rRNA and nox)
