Increased Prevalence of Symptomatic Human Intestinal Spirochetosis in MSM with High-Risk Sexual Behavior in a Cohort of 165 Individuals

Abstract

Human intestinal spirochetosis (HIS) can cause gastrointestinal symptoms, although asymptomatic infections have been described. Individuals from low-income countries, people living with HIV, and men who have sex with men (MSM) show increased risk. A retrospective review of all patients diagnosed with HIS (n = 165) between January 2013 and October 2020 at a tertiary hospital in Madrid, Spain, was performed to assess risk factors for symptomatic HIS, symptoms, and response to treatment. Most patients were male (n = 156; 94.5%), 86.7% were MSM, and 23.5% practiced chemsex, of whom most were symptomatic (p = 0.039). Most patients (78.4%) reported unprotected oral-anal intercourse. A total of 124 (81.1%) were symptomatic; diarrhea was the most common complaint (68.3%). Multivariable regression showed increased odds of symptoms associated with age under 41 (odds ratio 5.44, 95% CI 1.87-15.88; p = 0.002). Colonoscopy was normal in 153 (92.7%). Furthermore, 66.7% presented previous or concomitant sexually transmitted diseases (STDs). Among the patients, 102 underwent testing for other gastrointestinal pathogens, with positive results in 20 (19.6%). All symptomatic patients without concomitant gastrointestinal infection presenting improvement on follow-up (42 of 53) had received either metronidazole or doxycycline (p = 0.049). HIS should be considered as a cause of chronic diarrhea in MSM with high-risk sexual behavior after other causes have been ruled out; treatment with metronidazole is recommended. Coinfection with other STDs is common.

Keywords: Brachyspira; HIV infection; MSM; chemsex; diarrhea; histopathology; intestinal spirochetosis; metronidazole.

Figure 1

(A) Panoramic view of HIS with hematoxylin and eosin staining [10×]. (B) A 3 μm-thick basophilic fringe on the luminal surface of the enterocytes is visible (arrowheads) [40×]. (C) Spirochetes with Warthin-starry silver stain are observed (arrows). [40×] (D) Immunohistochemistry for anti-Treponema pallidum antibodies highlights spirochetes in dark brown-black color.

Figure 2

(A) Spirochetes attached to the colonic epithelium. (B) Detail of spirochetes disrupting the normal architecture of the human colon, invading the epithelium. (C) Biofilm formation of Brachyspira aalborgi. (D) Detail of spirochetes with their distinctive sinusoidal shape.