OBJECTIVE To investigate the mechanism of Gegen Qinlian decoction in treating antibiotic-associated diarrhoea(AAD) by regulating the intestinal flora as well as improving the intestinal immune function.

METHODS Sixty SD rats were divided into blank group, model group, positive drug(live bifidobacterium preparation capsules) group, high-, medium- and low- dosage groups of Gegen Qinlian decoction with ten rats in each group. Except for the blank group, the other groups were given clindamycin to induce AAD model, followed by 2 weeks of drug treatment. Morphological changes of the colon were observed using hematoxylin-eosin(HE); immunohistochemistry was used to detect immunity-associated factor activation-induced cytidine deaminase(AICDA), interferon regulatory factor 4(IRF4), X-box binding protein 1(XBP1), B-cell lymphoma 6 protein(BCL6), and immunoglobulin A(IgA); and macro-genomics sequencing was used to analyse the structural and functional changes in the faecal intestinal flora of rats in each group.

RESULTS Treatment with Gegen Qinlian decoction and positive drug repaired the morphology, structure, and mucosal epithelial cell damage of the colon in AAD rats, and up-regulated the expression of immune-related factors AICDA, BCL6, IRF4, XBP1, and IgA. Macro-genomics results showed that Gegen Qinlian decoction improved the diversity of intestinal microorganisms as well as the microbial abundance. At the phylum level, the Firmicutes/Bacteroidetes ratio was increased; at the genus level, the abundance of Ligilactobacillus, Lactobacillus, Limosilactobacillus, Romboutsia, Corynebacterium, and Enterococcus were increased; and at the intestinal function level, citrulline, lysine, cysteine, ornithine synthesis pathways were up-regulated, and intestinal lactic acid, acetic acid, propionic acid production pathways were up-regulated.

CONCLUSION Gegen Qinlian decoction can improve inflammatory injury, enhance intestinal immune response, and regulate the structure and function of intestinal flora in AAD rats.