阴沟肠杆菌定量标准物质的研制

Development of Quantitative Reference Material of Enterobacter Cloacae

采用真空冷冻干燥法和滤膜法定值技术,研制了球状的阴沟肠杆菌定量标准物质。经保护剂配方及冻干程序参数优化后,阴沟肠杆菌的平均存活率达51%,形状均匀一致、外观光滑无塌陷,能完全复水速溶。通过结晶紫中性胆盐琼脂培养基平板计数法考察均匀性和稳定性,证明该标准物质均匀性良好,-80℃至少可稳定保存6个月。该标准物质由6家实验室采用滤膜法联合定值,经不确定度评定,标称值为(2.0±0.1)log_(10)(cfu/瓶),相对扩展不确定度为10%(k=2)。标准物质中阴沟肠杆菌活菌数含量水平为10~2 cfu/瓶,可以直接溶解使用,无需稀释,使用方便,同时减少了测量不确定度来源。

A reference material in globular shape for the quantification of enterobacter cloacae was prepared by vacuum freeze drying and filter method. The viable count of enterobacter cloacae per sphere was measured in cfu value by filter membrane method. After optimizing the protective agent and freeze-drying process parameters, the average survival rate reached 51%. The reference material has uniform shape, smooth appearance and good reconstituability. The homogeneity and stability of the enterobacter cloacae reference material were determined by plate counting method on violet red bile agar （VRBA） culture media. The results showed that the reference material is homogeneous and stable for up to 6 months when stored at - 80 ℃. The reference material was characterized by six laboratories with filter membrane method on Endo Agar. The value of the reference material is （2.0 ± 0. 1 ）loglo （cfu/vial）, with the relative expanded uncertainty of 10 % （k = 2 ）. The content of viable count of enterobacter cloacae in the reference material is 102 cfu/vial, it can be dissolved directly, without dilution and easy to use, and this can reduce the sources of measurement uncertainty.