In 1967, Harland and Lee made a startling discovery: in some humans, the colonic epithelium was covered with a “forest” of spirochetes.
Intestinal spirochetes (IS) in humans are an enigma with regards to their biology, origin, and state (commensals or pathogens) in the human large intestine.
In animals, IS have been linked to diarrheal illness in swine, poultry, dogs, cats, opossum, non-human primates, and guinea pigs.
The presence of IS in human stool has been documented microbiologically throughout Africa, Australia, India, Indonesia, and much of the Western world for decades.
Particularly in children, IS may be associated with severe clinical symptoms.
The highest rates of colonization of stools with IS in developed countries are found in homosexual males and in human immunodeficiency virus (HIV)-infected individuals.
In many cases, the histological findings of IS are incidental discovery during a screening colonoscopy.
Symptomatic IS are most commonly accompanied by complaints of chronic (watery) diarrhea, vague abdominal pain without other apparent cause and bleeding per rectum.
The endoscopic appearance of the colon is usually non-contributory.
Colonic involvement has been documented from the proximal to the distal colon, including the rectum.
Biopsy: surface of colonic mucosa shows a diffuse blue fringe (seen in hematoxylin-eosin stain), which is approximately 3 to 6 μm thick, along the border of the intercryptal epithelial layer. This finding is referred to as the "false brush border".
Although molecular genetic techniques separate the different spirochetal species specifically, the diagnosis of IS has still to be ascertained morphologically in the biopsy material.
Once the diagnosis is confirmed, work-up for relevant co-morbid conditions such as HIV, etc. need to be done.
Generally, a trial of antibiotic therapy is warranted, however, the response is variable.
References
Norris SJ. Hiding in Plain Sight: Colonic Spirochetosis in Humans. J Bacteriol. 2019:e00465-19.
Tsinganou E, Gebbers JO. Human intestinal spirochetosis--a review. Ger Med Sci. 2010;8:Doc01.
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