单增李斯特菌选择性增菌培养分离的初步探讨

Isolation and cultivation of Listeria

目的:寻找一种良好的增菌培养分离法,提高食品中单增李斯特菌(Lm)的检出率。方法:对Fraser肉汤增菌法进行改良,在自行配制的第一液Half-Fraser肉汤中添加氯霉素,观察其对Lm及蜡样芽孢杆菌(B.cereus)的影响,确定加入氯霉素的最佳适宜量。160份样品同时采用改良Fraser肉汤法、FDA法、国标法增菌培养后,用传统生化鉴定Lm,比较检出率。结果:在Half-Fraser肉汤中添加3.0μg/ml氯霉素不会对样品中的Lm产生明显的影响,但可有效抑制B.cereus的生长。3种增菌培养法以Fraser肉汤增菌法总检出率最高,尤其对速冻食品的检出率达100%,FDA法对灭菌食品的检出率达100%。结论:Half-Fraser肉汤氯霉素的最佳添加量为3.0μg/ml。不同样品类型要用不同的增菌法,必要时用2种以上方法相结合,提高食品中Lm的检出率。

Objective：To find out a good method for isolating and culturing and to increase the detecting rate of the PCR rapid detection on the Lm in the food. Methods：Developing frasers, adding chloramphenical in the first liquid （self - made） - Half - Fra- ser,observe its influence on the Lm and B. cereus and decide the most appropriate amount of chloramphenicol. In 160 samles, we all adopted the improved fraser, FDA, international culturing, and then examine the Lm with the PCR and compare the detecting rate. Results：There was no influence obvious on the Lm of the Half- Fraser and it can effectively control the growth of B. cereus. In the three methods for culturing,the highest total detecting rate was in the fraser,espscially that on the quick -freezed food. The detecting rate was up to 100% and the detecting rate on the sterile food tested by FDA was also up to 100%. Conclusion：The most appropricte amount of chloramphenicol in the Half - Fraser is 3.0 μg/ml. Different types of sample need different culturing and one even needs two or more than two methods when necessary to increase the detecting rate of Lm in the PCR rapid detection.