中药水提物对猪源耐四环素大肠杆菌的抑制活性

【目的】了解中药水提物对猪源耐四环素大肠杆菌的抑制活性，为其在养猪生产中的应用提供依据。【方法】纸片法测定10个猪源大肠杆菌分离株对四环素的敏感性，PCR方法测定其对四环素耐药基因的携带情 况；琼脂扩散法和微量倍比稀释法测定中药水提物及其与四环素的混合物对10个猪源大肠杆菌分离株的抑制活性。【结果】10个受试菌株对四环素的耐药率达100%，部分或全部菌株携带tetA（10/10）、tetB（2/10）和tetC（9/10）等四环素耐药基因；山楂、五味子、连翘和金银花的水提物均有较强的抑菌活性，但与四环素混合后，其抑菌圈直径减小，最小抑菌浓度增大。【结论】受试菌株对四环素的耐药性可能由tetA、tetB和tetC等四环素耐药基因引起，测定的4种中药水提物对受试菌株均有抑制活性，但不宜与四环素联用。

Inhibitory Activity of Chinese Herbal Aqueous Extracts to Tetracycline-Resistant E. coli of Swine

【Objective】 This study was conducted to determine the inhibitory activity of Chinese herbal aqueous extracts to tetracycline-resistant E. coli of swine in order to provide a basis for their application in the swine production. 【Method】 Paper disk method and PCR method were used to evaluate tetracycline sensitivity to 10 isolates of E. coli of swine and their tetracycline-resistance genes, respectively, as well as the agar diffusion and double dilution to test the inhibitory activity of Chinese herbal aqueous extracts and their mixtures with tetracycline to 10 isolates of resistant E. coli of swine. 【Result】 All of the 10 tested isolates were resistant to tetracycline, 10 of which carried the tet A, two of which carried tet B, and 9 of which carried tet C. The extracts of Fructus crataegi, Fructus forsythiae, Flos lonicerae and Fructus schisandrae had stronger antibacterial activity, while their mixtures with tetracycline presented the decreased inhibition zone diameter and increased minimal inhibitory concentration. 【Conclusion】 The tetracycline resistance of the tested strains was related to the existances of resistance genes, including tetA, tetB and tetC. The extracts of 4 Chinese herbs tested in this study had stronger inhibitory activity against the isolates of E. coli, and could not be used with the tetracycline togather.