Nakamura Hiromi, Tokuda Yuka, Sono Ayumi, Koyama Tomoka, Ogasawara Jun, Hase Atsushi, Haruki Kosuke, Nishikawa Yoshikazu
Department of Food and Human Health Sciences, Graduate School of Human Life Science, Osaka City University, Japan.
J Food Prot. 2006 Apr;69(4):835-41. doi: 10.4315/0362-028x-69.4.835.
In this study, Listeria monocytogenes contamination in a cold-smoked fish processing plant in Osaka, Japan, was examined from 2002 to 2004. A total of 430 samples were collected and divided into five categories: raw fish, materials during processing, processing equipment, environment, and finished products. A total of 59 finished products were examined throughout this study. L. monocytogenes was isolated from four of these samples during summer and autumn but was not found during winter or spring. During the warmer seasons, L. monocytogenes was more prevalent on processing equipment, especially slicing machines (8 of 54 samples in summer and autumn versus 1 of 50 samples in winter and spring). L. monocytogenes was not detected on whole skins removed from 23 frozen raw fish. L. monocytogenes strains isolated from 56 samples were characterized by serotyping, pulsed-field gel electrophoresis, and three PCR-based methods. Seventy-seven L. monocytogenes strains were recognized as contaminants of the samples: 2 distinguishable strains were identified in each of 13 samples, 3 strains were identified in 2 samples, 5 strains were identified in 1 sample, and the other 40 strains were identified in 40 samples. Combining the results from these techniques, 77 strains were classified into 13 different types. Three of these types prevailed throughout the plant, and two of the three were also isolated from final products. The DNA subtype found in the product was also found on the slicing machines. Our findings suggest that the slicing machines at this plant were the source of the product contamination. Implementing an appropriate cleaning regime for the slicing machines was effective in preventing contamination.
在本研究中，于2002年至2004年对日本大阪一家冷熏鱼加工厂中的单核细胞增生李斯特菌污染情况进行了检测。共采集了430个样本，并分为五类：生鱼、加工过程中的原料、加工设备、环境和成品。在整个研究过程中，共检测了59个成品。在夏季和秋季，从其中4个样本中分离出了单核细胞增生李斯特菌，但在冬季或春季未发现。在温暖季节，单核细胞增生李斯特菌在加工设备上更为普遍，尤其是切片机（夏季和秋季54个样本中有8个，而冬季和春季50个样本中有1个）。从23条冷冻生鱼去除的完整鱼皮上未检测到单核细胞增生李斯特菌。从56个样本中分离出的单核细胞增生李斯特菌菌株通过血清分型、脉冲场凝胶电泳和三种基于PCR的方法进行了鉴定。77株单核细胞增生李斯特菌菌株被认定为样本的污染物：13个样本中各鉴定出2个可区分的菌株，2个样本中鉴定出3个菌株，1个样本中鉴定出5个菌株，其他40个菌株分别在40个样本中鉴定出。综合这些技术的结果，77株菌株被分为13种不同类型。其中三种类型在整个工厂中普遍存在，这三种类型中的两种也从最终产品中分离出来。在产品中发现的DNA亚型在切片机上也被发现。我们的研究结果表明，该工厂的切片机是产品污染的源头。对切片机实施适当的清洁制度可有效防止污染。
