ObjectiveTo investigate the modulating effect of modified Wumeiwan （MWMW） on the ulcerative colitis （UC）-associated intestinal helper T cell 17 （Th17）/regulatory T cell （Treg） balance and intestinal flora by using a human flora-associated model of UC patients with dampness-heat obstruction syndrome， thus providing a new idea for the UC-related research and therapeutic strategies. MethodsThe 24 male C57BL/6J mice were randomized into normal control， model， and MWMW groups （n=8）. Model and MWMW groups were first treated with an antibiotic cocktail （vancomycin， 0.1 g·kg^-1； neomycin sulfate， 0.2 g·kg^-1； ampicillin， 0.2 g·kg^-1； metronidazole， 0.2 g·kg^-1） for 21 days. At the end of antibiotic treatment， the gavage of fecal microbiota suspension from UC patients with dampness-heat obstruction syndrome was started at a dose of 0.2 mL·d^-1 for 19 consecutive days， by which a human flora-associated model of UC was obtained. The MWMW group was administrated daily with MWMW liquid （12.5 g·kg^-1）， while the normal control and model groups were administrated by gavage with an equal amount of sterile water for 7 consecutive days. The symptoms of dampness-heat obstruction were observed. The colon length and spleen index were measured and calculated， and the proportions of Th17 and Treg cells were detected by flow assay. The intestinal flora was analyzed by 16S rRNA high-throughput sequencing. ResultsCompared with the normal control group， the model group showed shortened colon （P<0.05） and increased spleen index （P<0.01）. Compared with the model group， the MWMW group showed prolonged colon （P<0.01） and decreased spleen index （P<0.05）. After the intervention of MWMW， the Th17 proportion and Th17/Treg ratio in the colon decreased （P<0.01）， and the proportion of Treg cells increased （P<0.05）. The number of species and alpha and beta diversity of intestinal flora in mice were regulated by MWMW （P<0.05）. In terms of intestinal flora composition， MWMW increased the relative abundance of several phyla （Firmicutes， Proteobacteria， Fusobacteriota， Actinobacteriota， and Gemmatimonadota）， the genus Bacteroides， and two species （Bacteroides thetaiotaomicron and B. fragilis） in model mice. Moreover， Spearman's correlation analysis showed that the relative abundance of B. thetaiotaomicron and B. fragilis were negatively correlated with the Th17 level （P<0.05）. In addition， the above changes in intestinal flora caused the changes in microbial genes involved in 14 pathways， such as glycolysis， amino acid degradation， inorganic nutrient metabolism， biosynthesis of pyrimidine deoxyribonucleotides， antibiotic resistance， and degradation of polysaccharides. ConclusionsThe human flora-associated model successfully simulated the changes （marked by a decrease in the abundance of Bacteroides） of intestinal flora in UC patients with dampness-heat obstruction syndrome. MWMW can enrich the abundance of beneficial bacteria such as B. thetaiotaomicron and B. fragilis and promote the synergistic intestinal immune modulation with the metabolic functions centered on glycolysis， amino acid metabolism， and nucleotide synthesis through bacterial polysaccharide utilization sites to reduce the Th17/Treg ratio， thereby exerting a protective effect on UC.