【摘要】 目的 本研究旨在探讨甘草是否具备预防大肠杆菌K99感染或缓解其所引发症状的作用。方法 通过水煎法制备浓度为1.6 g/mL的甘草提取液，选用体重32 g左右的昆明小鼠35只，随机分为5组，分别按8 g·kg^-1·d^-1和4 g·kg^-1·d^-1的剂量用甘草提取液灌胃小鼠7 d，第8 d灌胃浓度为10⁸ CFU/mL的大肠杆菌K99诱导小鼠腹泻。随后检测小鼠血清中炎症因子，计算小鼠免疫器官指数并进行肠道菌群分析。结果 结果表明，大肠杆菌K99可引起小鼠腹泻、免疫器官变化、肠道菌群失调和炎症反应；甘草提取液可增加小鼠肠道菌群丰度，提高拟杆菌、乳杆菌等的相对丰度并降低变形菌、脱硫弧菌等的相对丰度；灌胃甘草提取液的小鼠受到大肠杆菌K99侵袭时，免疫器官指数和血清炎症因子（肿瘤坏死因子-α、白细胞介素-1β和白细胞介素-6）含量正常，肠道菌群平衡。结论 灌胃甘草提取液可通过抑制血清中炎症细胞因子水平上升并改善肠道菌群，减轻由大肠杆菌K99引起的小鼠免疫器官反应和机体炎症，降低小鼠腹泻率。为甘草提取液预防由大肠杆菌K99导致的犊牛腹泻提供了思路。更多还原

【Abstract】 Escherichia coli K99, an enterotoxigenic Escherichia coli（ETEC）, is the main strain that causes bacterial diarrhea in newborn calves, thus resulting in substantial economic losses in the cattle breeding industry. The aim of this study was to investigate whether licorice might prevent E. coli K99 infection or alleviate related symptoms.Licorice extract at a concentration of 1.6 g/mL was prepared by decoction, Thirty-five Kunming mice weighing approximately 32 g were randomly divided into five groups. The mice were gavaged with licorice extract at doses of 8 g·kg^-1·d^-1 or 4 g·kg^-1·d^-1 for 7 days, and E. coli K99 at a concentration of 10⁸ CFU/mL administered on the 8 th day induced diarrhea in the mice. Subsequently, the inflammatory factors in the serum were detected, the immune organ index was calculated, and the intestinal microbiota was analyzed. E. coli K99 was found to cause diarrhea, immune organ changes, intestinal flora dysbiosis, and inflammatory responses in the mice. Licorice extract increased the intestinal microbiota richness, improved the composition of dominant microflora, and increased the number of beneficial bacteria; moreover, under E. coli K99 infection, the immune organ index and serum inflammatory factors（tumor necrosis factor-α, interleukin-1β, and interleukin-6） were normal, and the intestinal microbiota was balanced. In conclusion, gavage of licorice extract decreased the immune organ response and body inflammation caused by E. coli K99, and decreased diarrhea rate in mice, by inhibiting increased inflammatory cytokine levels in the serum and improving the intestinal flora. This study provides a theoretical basis for the use of licorice extract to prevent calf diarrhea caused by Escherichia coli K99.更多还原