[Immunohistochemical diagnosis of colonic spirochetosis with anti-treponema antibody in patients consulting for chronic diarrhea. Results of a prospective study conducted in 137 patients].

Aim: To assess the incidence of colonic spirochetosis, diagnosed by immunohistochemical stain with anti-Treponema pallidum antibody, in a prospective study of colonic biopsies of patients presenting with chronic diarrhea.

Material And Methods: From March 2017 to March 2018 the colonic biopsies of patients presenting with chronic diarrhea were stained with Hematoxylin Eosin and anti-Treponema pallidum antibody. The positive cases were also stained with Steiner stain.

Results: A total of 137 colonic biopsies were assessed and 3 cases were positive for immunohistochemical stain with anti-Treponema pallidum antibody (2% of the patients). One case was easy to diagnose with HE stain but the 2 other cases were not. The bacteria were stained with Steiner stain, but less easily seen than with the immunohistochemical stain. No patient was treated with antibiotics.

Discussion And Conclusion: The colonic spirochetosis can be easily diagnosed by pathologists with immunohistochemical stain with anti-Treponema pallidum antibody. The bacteria are more easily diagnosed with immunohistochemical stain than with HE stain or Steiner stain. However, colonic spirochetosis is rarely diagnosed on colonic biopsies of patients presenting with chronic diarrhea (2% of the patients in our study). Due to the rarity of the entity, and the cost of immunohistochemical stain and the weak benefit for the patient (no patient in our study was treated with antibiotics for colonic spirochetosis) we cannot advise to perform systematic immunohistochemical stain with anti-Treponema pallidum antibody in all the colonic biopsies of patients presenting with chronic diarrhea.