Immunohistochemistry application as step one for diagnosing human intestinal spirochetosis

Abstract

Diagnosing human intestinal spirochetosis (HIS), a colorectal infectious disease caused by Brachyspira species bacteria, in routine practice depends histologically on the presence of the so-called fringes on the mucosal epithelial surface. Cases in which hematoxylin-eosin (HE) sections raise suspicions of HIS may be further examined using immunohistochemistry (IHC). We aimed to elucidate whether an initial IHC application might increase the proportion of cases considered HIS-suspicious. Focusing on the fringes, we compared HIS diagnosed by HE (HIS-HE) and by IHC (HIS-IHC; based on results obtained using a polyclonal anti-Treponema pallidum antibody) in one month's consecutive lower GI endoscopic specimens in the pathology department at a single hospital. Among the 140 individuals examined during the period, 10 HIS-IHC cases (7.1%; M:F=5:5; 34-75 yrs; median 57 yrs) were diagnosed, while HE pathology found eight HIS-HE cases (the fringes were thick and distinct; 5.7%) and two possible cases. All 8 HIS-HE cases matched HIS-IHC cases. However, the two possible HIS-HE cases were denied by IHC, while two of the HIS-IHC cases were overlooked by HE pathology. Among the 10 HIS-IHC cases, 8 cases had conventional adenomas, 1 sessile serrated adenoma/polyp, 2 microvesicular hyperplastic polyps, 3 goblet cell rich hyperplastic polyps, and 1 ulcerative colitis. Cases with goblet cell rich hyperplastic polyps were at a higher rate in HIS than in non-HIS cases (p < 0.01). In conclusion, an initial IHC application might detect more HIS cases in routine practice, and importantly it might help to establish a correct diagnosis of HIS.