Miettinen Hanna, Wirtanen Gun
VTT, P.O. Box 1000, FI-02044 VTT, Finland.
Int J Food Microbiol. 2006 Nov 1;112(2):138-46. doi: 10.1016/j.ijfoodmicro.2006.06.016. Epub 2006 Jul 13.
This study focused on the ecology of Listeria monocytogenes in a fish farm by following the changes in its occurrence in different types of samples for a three year period. In addition, L. monocytogenes isolates from different seafood industry areas were compared with pulsed field gel electrophoresis (PFGE) typing to discover possible associations between primary production, further processing and final products. Weather conditions were found to have a strong influence on the probability of finding Listeria spp. in a fish farm environment. The number of samples contaminated with Listeria spp. was typically bigger after rainy periods. Brook and river waters as well as other runoff waters seemed to be the main contamination source at the farm studied. The farmed fish originally found to carry L. monocytogenes become gradually Listeria free. The time needed for the purification of the fish was several months. The sea bottom soil samples were the ones that preserved the L. monocytogenes contamination the longest time. It can be stated that the fish and fish farm equipment studied did not spread listeria contamination. On the contrary, they were found to suffer from listeria contamination coming from outside sources like the brook water. There was a wide range of different L. monocytogenes PFGE-pulsotypes (30) found at 15 Finnish fish farms and fish processing factories. L. monocytogenes isolates from the final products often belonged to the same pulsotypes as did the isolates from the processing environment as well as from the raw fish. This suggests that, in addition to the fish processing factory environment, the fish raw materials are important sources of L. monocytogenes contamination in final products.
本研究通过追踪三年期间不同类型样本中单核细胞增生李斯特菌的出现变化，聚焦于一个养鱼场中该菌的生态学。此外，运用脉冲场凝胶电泳（PFGE）分型法对来自不同海产品行业区域的单核细胞增生李斯特菌分离株进行比较，以发现初级生产、进一步加工与最终产品之间可能存在的关联。研究发现天气条件对在养鱼场环境中发现李斯特菌属的可能性有很大影响。雨后被李斯特菌属污染的样本数量通常更多。溪流和河水以及其他径流似乎是所研究养鱼场的主要污染源。最初发现携带单核细胞增生李斯特菌的养殖鱼类逐渐不再携带该菌。鱼类净化所需时间为几个月。海底土壤样本中单核细胞增生李斯特菌的污染持续时间最长。可以说，所研究的鱼类和养鱼场设备并未传播李斯特菌污染。相反，它们受到来自诸如溪水等外部来源的李斯特菌污染。在芬兰的15个养鱼场和鱼类加工厂发现了广泛多样的不同单核细胞增生李斯特菌PFGE脉冲型（30种）。最终产品中的单核细胞增生李斯特菌分离株通常与加工环境以及生鱼中的分离株属于相同的脉冲型。这表明，除了鱼类加工厂环境外，鱼原料也是最终产品中单核细胞增生李斯特菌污染的重要来源。
