Segmented filamentous bacteria are associated with disease activity in children with inflammatory bowel disease

Objectives This study aimed to determine the positivity rate of segmented filamentous bacteria (SFB) in pediatric patients with inflammatory bowel disease (IBD) and to evaluate its association with disease activity. Methods In this cross-sectional study, 30 pediatric IBD patients and 30 children with functional gastrointestinal disorders were enrolled. SFB in ileal lavage fluid from the terminal ileum were detected using polymerase chain reaction. IBD patients were stratified according to treatment status and disease activity—Untreated Active (UTA), Treated Remission (TRR), Treated Active (TRA)—as well as by disease type (Crohn's disease or ulcerative colitis). SFB positivity rates were compared across subgroups. Within the IBD cohort, disease activity and inflammatory markers, including fecal calprotectin, C-reactive protein, erythrocyte sedimentation rate, platelets count, were compared between SFB-positive and SFB-negative patients. Results The SFB positivity rate was significantly higher in pediatric IBD patients than in controls (63.3% vs. 36.7%, P = 0.038). Subgroup analysis showed that the UTA group had the highest SFB positivity rate (82.4%), which was significantly higher than both the control group ( P = 0.002) and the TRR group (28.6%, P = 0.021). Among TRA group, the SFB positivity rate remained elevated (50.0%). The positive rate did not differ significantly from that of the UTA group ( P > 0.05). The SFB positivity rate was higher in pediatric Crohn's disease patients (66.7%, 14/21) than in controls but showed no significant difference compared with ulcerative colitis ( P > 0.05). SFB-positive patients exhibited significantly higher disease activity indices (PCDAI, P = 0.005; PUCAI, P = 0.021) and elevated inflammatory markers (fecal calprotectin, P = 0.001; C-reactive protein, P = 0.001; erythrocyte sedimentation rate, P = 0.001) compare with SFB-negative patients. Conclusions SFB positivity occurred more frequently in pediatric IBD than in controls—especially in active disease—and was associated with higher inflammatory activity and disease severity.