Human Intestinal Spirochetosis Shows Higher Positivity in Sessile Serrated Lesions Than in Tubular Adenomas With Preferential Colonization of Absorptive Epithelium

Factors underlying differential colonization by human intestinal spirochetosis (HIS) of various colorectal neoplastic lesions remain unclear. We compared HIS positivity and colonization patterns between sessile serrated lesions (SSLs) and tubular adenomas (TAs) and examined the relationship between spirochetal distribution and epithelial differentiation. HIS positivity was significantly higher in SSLs than TAs at both lesion (26/590 [4.4%] vs. 3/536 [0.6%], p < 0.001) and case (16/421 [3.8%] vs. 1/171 [0.6%], p = 0.03) levels. Because the SSL and TA main cohorts covered different periods, nine HIS‐positive SSL cases harboring TAs diagnosed outside the TA cohort period were separately analyzed for within‐case comparison, confirming significantly higher HIS positivity in SSLs than TAs (11/12 [91.7%] vs. 6/23 [26.1%], p = 0.003). Among HIS‐positive lesions, both SSLs and TAs showed reduced colonization at lesion sites compared to surrounding mucosa, with greater reduction in TAs. GS‐II staining demonstrated reduced terminal βGlcNAc on HIS bacterial bodies at SSL lesion sites. HIS preferentially colonized absorptive epithelium, although less evidently in TAs with limited absorptive differentiation. All cases harbored only Brachyspira aalborgi . These results indicate that HIS exhibits universal affinity for absorptive epithelium and that higher HIS positivity in SSLs reflects their greater abundance of absorptive epithelium.