Intestinal spirochetes. Organisms in search of a disease?

The field of gastroenterology includes many examples of organisms whose pathogenicity has been questioned in the past. Older members of the American Society for Clinical Pathology might remember the skepticism with which the original publications by Warren 1 and Marshall 2 detailing the description of Helicobacter pylori associated with chronic active gastritis were greeted. It was not until Koch's postulates were fulfilled by having a volunteer ingest the organism that the bacterium was accepted as a pathogen. 3 We now accept that H pylori, while present as an asymptomatic infection in many people, is a pathogen with a large variety of manifestations. On the other hand, the pathogenic status of Blastocystis hominis probably will never be resolved satisfactorily. In this issue of the Journal, Koteish and colleagues 4 present a retrospective review of 14 cases in which endo-scopic biopsies revealed the presence of spirochetes in the colon. The study raises many interesting questions about the clinical and pathogenic significance of these organisms but provides few definitive answers. Genotypic analysis of 13 of the cases indicated that 11 patients were infected with Brachyspira aalborgi, while the remaining 2 patients had Brachyspira pilosicoli infections. The predominance of B aalborgi as the intestinal spirochete was confirmed by a recent study from Australia with similar findings. 5 Six of the patients had symptoms, which was the reason for biopsy: 2 HIV-infected men and all 4 of the children. The remaining patients, who were all adults, were asymptomatic and underwent biopsy for reasons other than diarrhea or abdominal pain. Two patients were treated with antibiotics. The 1 patient for whom follow-up information was available had complete resolution of symptoms. Two of the asymptomatic adults had follow-up biopsy, with spirochetes found in the specimen from one of these patients. Interestingly, even in symptomatic patients, the presence of spirochetes, which were found throughout the colon, was not associated with active inflammation , mucosal damage, or histologic changes consistent with chronic infection. What are we to make of these findings? Because this case series involved a search of the surgical pathology files in a large tertiary care hospital from January 1994 to January 2002, the prevalence of intestinal spirochetosis, whether symptomatic or asymptomatic, may be low. However, Koteish and colleagues 4 reported that spirochetes are present in the colon in approximately 2.5% to 16% of people from Western countries, 6,7 with prevalence rates as high as 50% in …