Intestinal spirochaetosis causing chronic diarrhoea in a patient with HIV infection

Background

Diarrhoea is a common presenting complaint in HIV-infected individuals, which can be due to a multitude of aetiologies ranging from infectious pathogens to medication. Patients should be investigated fully and referred appropriately to gastroenterology.

Case report

A 36-year-old Caucasian homosexual man was diagnosed HIV positive in March 2009 after routine asymptomatic screening, having had a negative test eight years previously. Baseline bloods showed a CD4 count of 790 cells/µL (42%) and plasma HIV RNA of 439 copies/ml. On system review at diagnosis, the patient reported chronic non-bloody, watery diarrhoea for four years, which had never been investigated. His CD4 count dropped to 370 (31%) in August 2011 and he, therefore, commenced combination antiretroviral therapy (cART) with Truvada® and ritonavir-boosted darunavir.

Despite full virological suppression within two months of starting, the diarrhoea persisted on average five days a week, 2–3 motions a day with abdominal cramps worse prior to defaecation. There were no specific food types that exacerbated his symptoms, no family history of gastrointestinal disease and no relevant travel history. The diarrhoea began to interfere with his work, and he lost his job due to regular sick leave and one episode of faecal incontinence. Multiple stool samples were negative on culture and on microscopy for ova, cysts and parasites. Serology for coeliac disease was negative. A sexual health screen was negative, his HIV viral load remained undetectable, and his CD4 count rose to 700 cells/µL (50.4%). Consideration was given to switching his cART regimen in case the darunavir was contributing to his diarrhoea, but the patient was adamant that this had made no difference.

He was, therefore, referred to the Gastroenterology department for further advice. Faecal calprotectin and elastase levels were normal. Appearances of the large and small bowel mucosa were normal at colonoscopy. However, microscopy of stained large bowel mucosal biopsies revealed widespread infestation by spirochetes on the luminal aspect of the epithelial cells (Figure 1). PCR identification of the microorganism was not performed. He was treated with a two-week course of oral metronidazole (400 mg tds). At follow-up, the patient reported that the diarrhoea had resolved completely and, as a result, his quality of life has improved greatly. A follow-up colonoscopy and biopsy were not performed as the patient declined an invasive procedure. OPEN IN VIEWER

Previous case reports have demonstrated intestinal spirochaetosis after being diagnosed HIV positive. This case, however, highlights the need for thorough systematic review at baseline and potential investigations of any pre-existing symptoms before starting cART – if immunocompetent. cART may often be the reason for gastrointestinal disturbances, but this case demonstrates that this is not always so. Furthermore, valuing the patient’s perspective of their symptoms is extremely important and relevant in this case to avoid any unnecessary alterations to their management.

Discussion

Intestinal spirochaetosis was first described in 10 symptomatic patients by Harland and Lee. ¹ Brachyspira aalborgi and Brachyspira pilosicoli are the most common organisms isolated, and the mode of transmission is unclear. Human intestinal spirochaete populations are not related to non-intestinal spirochaetes such as Treponema pallidum. ² The spirochaetes colonise the luminal surface of the colonic and appendiceal epithelial cells. Colonisation with the spirochetes may cause the patient to become symptomatic; however, most healthy individuals colonised with these spirochetes remain asymptomatic. However, immunosuppressed patients may develop opportunistic infection leading to chronic diarrhoea. ³

Men who have sex with men (MSM), whether HIV positive or negative are known to be at high risk of being colonised and are more likely to be symptomatic. ⁴ They are mostly affected by the spirochete B. pilosicoli. ⁴ The prevalence of intestinal spirochetosis is reported to be 2–7% in Western countries, 11–34% in less developed countries and up to 54% in MSM and HIV-infected patients. ⁵ Symptomatic patients with intestinal spirochaetosis typically experience prolonged watery diarrhoea, crampy abdominal pain or both. Endoscopic findings tend to be generally unremarkable with diagnosis typically made by biopsy and histology. ⁶ The organisms appear as a blue/purple hazy band on the luminal aspect of the epithelial cells of the mucosa. The Brachyspira species may also be identified by molecular techniques, such as PCR, that target ribosomal DNA on either faecal samples or paraffin-embedded tissue. ² A literature review in 2009 found 20 reported cases of intestinal spirochaetosis, all of whom were HIV-infected male patients from developed countries. Eighteen of the 20 cases had chronic watery diarrhoea, with some complaining of abdominal pain and weight loss. Colonoscopy often showed a normal mucosa, mild erythema or polypoid areas with the biopsies showing the presence of spirochetes. Treatment with metronidazole or penicillin led to the resolution of symptoms in every case. ⁷

In summary, intestinal spirochetosis should be considered in the differential diagnosis of patients with HIV infection and chronic diarrhoea without other apparent cause.