Genotyping Of Three Different Methods Tofood-borne Listeria Monocytogenes

Listeria monocytogeneis Gram-positive,short and rob-shaped pathogen,which couldcause serious disease to human and animals,at the same time,it was considered as one of thefour most serious food-borne pathogen by WHO.The susceptible population is the little baby,pregnant women,elderly and people who are weak in immune ability. The clinical feature isabortion, meningitics, pneumonia, enterite, septicemia, with a fatality rateof 20%~30%.LMis widely distributed in the environment, such as, all kinds of meat and their secondaryproducts,milk,seafood, instant food and so on. LM can adapt to surrounding environmenteasily, even under negative factors, like low temperature, high osmotic pressure, acid andantibiotic environment.Thus,it is meaningful to study how to check and find pollution sourcerapidly when listeria disease break out,genotyping technology is an important tool,and itsstability is closely related to the explanation and analysis to the result.This study chose RAPD、ERIC-PCR and Sau-PCR,three different genotyping methodsto investigate the subtyping of 22 LM fromthe supermarket,retail market in Guangzhou andand a food-processing company in Xiamen.There is difference and relation between theresults.The 22 LM was attributed into 11, 8 and 7subtypes respectively.They could alsodistinguish different serotyping,thus had a good resolution ratio and can be used to subtypeLM.Then 5 LM isolatedfrom 5 different places and different source and time were culturedand DNA was extracted from the cultures after 24 h,48 h and 72 h.In addition,the same strainswere subcultured daily and DNA was extracted from the culture after growth of 5,10,15 and20 subcultures. ERIC-PCR and Sau-PCR analysis demonstrated that the homology is higherthan 92% and 94% respectively. Indicating that the two typing methods is stable and can beused in epidemiology study.Then 12 LM strains were isolated from 100 raw pork samples by usingtraditionalbiochemical identification methods and PCR.These samples were from Xiamen,Zhangzhou,Longyan, and Changping.Then use Sau-PCR to subtype them and got 5 subtypes,implying good polymorphism.In this study,three different genotyping methods were used together to subtype LM andthe stability of ERIC-PCR and Sau-PCR were compared,which makes people have a betterunderstanding of LM and it’s helpful to monitor and track LM, thus can avoid the spread ofLM to a large scale.When using these genotyping methods in real life,it should according todifferent goals and requirements.