单核细胞增生李斯特菌的毒力基因检测及PFGE分型的研究

目的了解福建省食品中单核细胞增生李斯特菌携带hly、plcA、plcB和prfA毒力基因的情况及脉冲场凝胶电泳(PFGE)的分型情况。方法将hly、plcA、plcB和prfA基因作为靶序列选取4对引物,通过聚合酶链反应(PCR)检测61株单核细胞增生李斯特菌和2株可疑单核细胞增生李斯特菌的毒力基因,用PulseNet单核细胞增生李斯特菌标准方法进行7株单核细胞增生李斯特菌的PFGE分子分型。结果61株单核细胞增生李斯特菌毒力基因为hly 、plcA 、plcB 和prfA ,2株可疑单核细胞增生李斯特菌的毒力基因分别为hly-、plcA 、plcB-、prfA-和hly-、plcA-、plcB-、prfA-。7株单核细胞增生李斯特菌的PFGE分为5个型。结论实验结果表明福建省食品中分离到的单核细胞增生李斯特菌均含有hly、plcA、plcB和prfA基因,属于致病株。对2株可疑单核细胞增生李斯特菌进行了进一步的鉴定,排除了单核细胞增生李斯特菌,该毒力基因检测方法可用于可疑单核细胞增生李斯特菌的进一步鉴别。7株菌中有两对2株PFGE型别一致,一致的菌株来自不同年份不同销售地点的同一品牌,应用PFGE方法可以进一步调查该厂冻鸡肉中单核细胞增生李斯特菌的传播途径和污染源。

Virulence-Associated Genes and Molecular Sub-Typing of Listeria monocytogenes in Foods

Objective To understand the virulence-associated genes and the molecular sub-typing of the Listeria monocytogenes isolated from foods in Fujian Province.Method 61 strains of L. monocytogenes and 2 strains of presumptive L. monocytogenes isolated from raw meats were subjected to PCR assay for four virulence-associated genes, hly, plcA, plcB and prfA. 7 of the 61 strains of L. monocytogenes were genotyped by PulseNet pulsed-field gel electrophoresis (PFGE).Results The PCR assay revealed that the 61 strains of L. monocytogenes possessed all the four virulence-associated genes, hly, plcA, plcB and plcA the 2 strains of presumptive L. monocytogenes were hly~-, plcA~ ,plcB~-,prfA~- and hly~-, plcA~-,plcB~-,prfA~- by PCR. PFGE divided 7 strains of L. monocytogenes into 5 different genotypes.Conclusion The 61 strains of L. monocytogenes possessed all the four virulence-associated genes, indicating their pothogenicity. The 2 strains of presumptive L. monocytogenes were confirmed as L. innocua by further study. The virulence genes-targeted PCR holds a good promise as a rapid and reliable method for further identification of L. monocytogenes. 2 pairs of the 7 strains of L. monocytogenes genotyped by PFGE have been identified having same pulsotype and have been found previously in chicken products from the same factory. Despite different in time and place, this finding indicates that the PFGE method can be used for further investigation of the source and route of transmission of L. monocytogenes in the frozen chicken produced by that factory.