Laboratory of Food Microbiology and Immunology, Research Center for Animal Hygiene and Food Safety, Obihiro University of Agriculture and Veterinary Medicine, Japan.
Int J Food Microbiol. 2010 May 15;139(3):134-9. doi: 10.1016/j.ijfoodmicro.2010.03.025. Epub 2010 Mar 27.
Asazuke is a ready-to-eat Japanese light pickle, mainly made of vegetables which are known to be one of the sources of Listeria monocytogenes contamination. Although asazuke is a popular side-dish in Japan, the hazard of bacterial contamination has not been evaluated yet. In this study, we investigated the prevalence of L. monocytogenes, Salmonella spp., verotoxigenic E. coli (VTEC) and coliforms in 108 asazuke samples that randomly collected from supermarkets in Obihiro (Hokkaido prefecture, Japan) during the period of June to November 2007. Twelve (11.11%) L. monocytogenes were isolated with predominant serotype 4b (seven isolates) followed by 1/2a (two isolates), 1/2b, 3b and 4c (one isolate each) while Salmonella spp., VTEC and coliforms were not detected. All L. monocytogenes isolates demonstrated hemolytic activity by CAMP test and possessed all the virulence-associated genes (prfA, actA, mpl, inlA, inlC, plcA, plcB, hly, iap, clpC and opuCA) as resulted in PCR, thus revealed their potential pathogenicity. Moreover, 7 out of 12 isolates were from asazuke samples produced by the same factory and their pulsed-field gel electrophoresis (PFGE) profiles suggested that 6 of them were indistinguishable and one was different. L. monocytogenes contamination in the asazuke factory environment was further investigated and 23 out of 60 environmental swabs (38.33%) contained the bacterium. Comparison of PFGE profiles showed relatedness between food and environmental isolates indicating that contamination probably occurred in the asazuke factory during manufacturing. Interestingly, after HACCP training course conducted to the factory workers, 20 samples collected during the period of November to December 2008 were negative to L. monocytogenes revealing that the hygienic status has improved.
味噌腌菜是一种日本即食小菜，主要由蔬菜制成，而蔬菜是李斯特菌污染的来源之一。尽管味噌腌菜在日本是一种受欢迎的配菜，但细菌污染的危害尚未得到评估。在这项研究中，我们调查了 2007 年 6 月至 11 月期间从北海道网走市超市随机采集的 108 份味噌腌菜样本中李斯特菌、沙门氏菌、产肠毒素性大肠杆菌（VTEC）和大肠菌群的流行情况。从 12 份（11.11%）味噌腌菜中分离出李斯特菌，主要血清型为 4b（7 株），其次为 1/2a（2 株）、1/2b、3b 和 4c（各 1 株），而未检测到沙门氏菌、VTEC 和大肠菌群。所有李斯特菌分离株在 CAMP 试验中均表现出溶血活性，并通过 PCR 检测到所有与毒力相关的基因（prfA、actA、mpl、inlA、inlC、plcA、plcB、hly、iap、clpC 和 opuCA），表明其具有潜在的致病性。此外，12 株分离株中有 7 株来自同一家工厂生产的味噌腌菜，其脉冲场凝胶电泳（PFGE）图谱表明其中 6 株分离株无法区分，1 株分离株不同。进一步调查味噌腌菜工厂环境中的李斯特菌污染情况，发现 60 个环境拭子中有 23 个（38.33%）含有该菌。PFGE 图谱比较表明食品和环境分离株之间存在相关性，表明污染可能发生在生产过程中的味噌腌菜工厂。有趣的是，在对工厂工人进行 HACCP 培训课程后，2008 年 11 月至 12 月期间采集的 20 个样本均未检出李斯特菌，表明卫生状况有所改善。
