Objective  To explore the efficacy of composite Microecologics on colitis in rat with Crohn's disease (CD) induced by 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) and their impact on the intestinal flora.

Methods  SD rats were divided into four groups: Control, TNBS, Model (TNBS + Microecologics), and TNBS + 5-aminosalicylic acid (5-ASA). Each group contained four rats. Key parameters included body mass, disease activity index, colon length, and mucosal damage index scores. Colonic tissue was evaluated using hematoxylin-eosin (HE) staining, Masson staining, PAS glycogen staining, immunohistochemical analysis, Western blot, and ELISA to assess efficacy. Gut microbiota alterations were analyzed using 16s rRNA high-throughput sequencing.

Results  Compared with the TNBS group, the TNBS + Microecologics group showed a significant reduction in DAI scores (P < 0.05), improved colon shortening (from 14.53 cm to 17.67 cm, P < 0.05), lower mucosal damage scores (P < 0.01), and a marked decrease in collagen fiber proportion (from 24.18% to 12.36%, P < 0.01). The expression of the tight junction proteins ZO-1 (P < 0.05) and Claudin-1 (P < 0.01) was upregulated, and the number of goblet cells increased significantly (average count from 63 to 279.3, P < 0.01). Levels of inflammatory cytokines showed statistically significant differences: tumor necrosis factor α (TNF-α) (P = 0.001), interleukin (IL)-1β (P < 0.05), and IL-6 (P < 0.001) decreased, while IL-10 (P < 0.01) increased. Overall, the therapeutic effect of the microecological preparation was superior to that of the TNBS + 5-ASA group. Beta diversity of the gut microbiota in the Microecologics group improved significantly (P = 0.001). At the phylum level, compared with the Control group, the TNBS group showed a decreased relative abundance of Firmicutes (P < 0.01) and an increased abundance of Bacteroidetes (P < 0.001). Intervention with the microecological preparation reversed these changes, increasing Firmicutes (P < 0.05) and decreasing Bacteroidetes (P < 0.05) abundance compared with the TNBS group. The relative abundance of Chloroflexota was higher in the Control group than in the Microecologics group (P < 0.05). LEfSe analysis indicated significant enrichment of Lactobacillus following the microecological intervention.

Conclusion  Composite microecological preparations can play a therapeutic and remission-inducing role in Crohn's disease by reducing inflammatory factors, promoting the recovery of intestinal barrier function, and improving the balance of colonic microecology.