应用分子克隆常规质粒提取方法（略作修改），对一株Ｂｉｆ．ｉｎｆａｎｔｉｓＤＭ９２２７及另一株Ｌａｃｔｏ．ｃａｓｉｅ．ＤＭ８１２１进行质粒提取及分析，并用固体培养基药敏纸片法测定此两株菌对１７种常用抗生素的敏感性。结果发现，ＤＭ８１２１及ＤＭ９２２７中无质粒的存在。药敏结果显示，ＤＭ８１２１对强力霉素、链霉素、庆大霉素较敏感，而对头孢菌素、氨苄青霉素、青霉素耐药。ＤＭ９２２７对头孢菌素、先锋霉素、庆大霉素、卡那霉素较敏感，对氨苄青霉素、羧苄青霉素、青霉素、强力霉素等耐药。 Application molecular cloning routine plasmid extraction method (slightly modified), a Bif. infantisDM9227 and another strain of Lacto. casie. DM8121 for plasmid extraction and analysis, and the sensitivity of the two strains to 17 commonly used antibiotics was determined using the solid media susceptibility disk method. As a result, no plasmid was found in DM8121 and DM9227. Drug sensitivity results show that DM8121 is more sensitive to doxycycline, streptomycin, gentamicin, but cephalosporin, ampicillin, penicillin resistance. DM9227 cephalosporins, cephalosporins, gentamicin, kanamycin more sensitive to ampicillin, carbenicillin, penicillin, doxycycline and other resistance.