牛乳源大肠杆菌生物被膜形成及抗生素的作用

为研究大肠杆菌生物被膜（Biofilms，BF）对耐药性的影响及抗生素对BF形成的作用，以陕西关中地区乳房炎奶牛的乳样中分离的 35 株大肠杆菌为研究对象，通过刚果红琼脂和结晶紫染色法测定菌体形成 BF 的能力；通过药物敏感性试验检测 BF 形成前后菌体耐药性的变化；用结晶紫染色法结合荧光显微镜观察不同质量浓度抗生素对 BF 的影响。结果显示，35 株大肠杆菌中有 19 株（54.29%）为 BF 阳性，以形成强、中膜能力为主（84.21%）；大肠杆菌形成BF后使头孢噻呋、链霉素、四环素、环丙沙星、庆大霉素、青霉素的最小抑菌质量浓度及最小杀菌质量浓度分别提高4~16 倍和8~64 倍；抗生素对BF形成的抑制和清除作用随着药物质量浓度增大而加强，其中环丙沙星、头孢噻呋的效果较好。

Biofilm Formation and Antibiotics Resistance of Escherichia coli Isolated from Milk

In order to investigate the effects of biofilm on antimicrobial resistance and the effect of antibiotics on biofilm formation of Escherichia coli,35 E.coli strains were isolated from bovine mastitis cases in Guanzhong area of Shaanxi province,and the ability of biofilm formation was determined by Congo Red agar and crystal violet staining. The drug sensitivity test was used to detect the change of bacterial resistance before and after biofilm formation.The effect of different concentrations of antibiotics on biofilm was observed by crystal violet staining method combined with fluorescence microscopy.The results showed that 19 strains (54.29%)of the 35 E.coli strains were biofilm positive, mainly with strong and medium film forming capacity (84.21%). After the formation of biofilm, the minimum inhibitory concentration and minimum bactericidal concentration of E.coli to ceftiofur,streptomycin, tetracycline, ciprofloxacin,gentamicin and penicillin were increased by 4-16 times and 8-64 times, respectively. With the increase of drug concentration, the effects of inhibiting biofilm formation and clearing biofilm were enhancedand ciprofloxacin and ceftiofur have better effects among them.