基于ActA基因的单核细胞增多性李斯特菌的序列分型研究

根据单核细胞增多性李斯特菌ActA基因序列保守区设计一对引物，对21个菌株进行PCR扩增，得到长度为820bp的片段。PCR产物经过纯化后直接测序，并对其中的506bp进行同源性分析。结果表明单核细胞增多性李斯特菌分离株具有5个明显不同的克隆谱系，每个谱系的同源性均在95％～100％。16个单核细胞增多性李斯特菌奶相关和环境分离株可被分成4个谱系，其中2个谱系（C、D）均为奶相关分离株和成品奶分离株；加工厂地面污水分离株为独立的一个谱系。初步表明，成品奶中污染的单核细胞增多性李斯特菌来自于奶牛场，而非加工环境。

ActA gene sequence typing of Listeria monocytogenes

Using ActA-based DNA sequence typing procedure, a pair of primers was designed for PCR amplification of a 820 bp DNA fragment. The products from 21 Listeria monocytogenes strains were submitted directly for sequencing. The sequences of 506 bp within the amplified fragments were aligned by Clustal V for phylogenetic analysis. All L. monocytogenes strains were grouped into five clusters. Clusters A,D and E were related to milk including raw milk,homogenized milk and pasteurized milk,while the strains isolated from sewages and other processing environments were in an independent cluster. These results indicate that L. monocytogenes strains contaminating the pasteurized milk products most probably came titan raw milk but not titan processing environments.