Indiana University School of Medicine Indianapolis, Indiana
Introduction: Human intestinal spirochetosis (IS) is a condition defined histologically by the presence of spirochetal microorganisms attached to the apical cell membrane of the colorectal epithelium. Children, homosexual and HIV-positive patients are at higher risk. Prevalence rates of IS are low where living standards are high, in contrast to less developed regions where IS is relatively more common.
Case Description/Methods: Our subject is a 39 year old male with a background history of HIV infection on treatment, with a viral load of 43 at the time of presentation and a CD4 count of 400. He presented with a large volume watery diarrhea, up to 4 liters a day, on and off for several weeks prior to his admission. The patient also had abdominal pain and cramping, in addition to an intermittent fever up to 102 F. The patient underwent a full work up including stool cultures that came back negative for Giardia, Cryptosporidium, Salmonella, Shigella, Campylobacter, and E. coli O157. The patient was also tested for C.diff twice and both came back negative. Colonoscopy was done for further investigation of the ongoing diarrhea and showed normal-looking colonic mucosa which was biopsied to rule out microscopic colitis. Pathology results came back with IS, as shown in images (A,B, and C). The patient was treated with metronidazole and with subsequent resolution of symptoms.
Discussion: The most common organisms causing IS in humans are Brachyspira spp, mostly commonly Brachyspira aalborgi and Brachyspira pilosicoli. These organisms are difficult to grow in artificial culture media and their pathogenicity is debated. A review of the literature suggests that invasion of spirochetes beyond the surface epithelium may be associated with gastrointestinal symptoms which respond to antibiotic treatment, whereas individuals lacking this feature may be mostly asymptomatic. Interestingly, the severity of symptoms does not seem to correlate with degree of immunodeficiency in HIV positive individuals. Rare cases of spirochetemia and multiple organ failure have been reported in critically ill patients with IS. Clinical suspicion to investigate and pathological knowledge of potential pathogenicity in certain clinical scenarios are keys in diagnosing and eventually treating IS.
