Abstract：
Frozen vegetables have emerged as a concern due to their association with foodborne outbreaks such as the multi-country outbreak of Listeria monocytogenes serogroup IVb linked to frozen corn. The capacity of L. monocytogenes to colonize food-processing environments is well-known, making the bacteria a real problem for consumers. However, the significance of the processing environment in the contamination of frozen foods is not well established. This study aimed to identify potential contamination niches of L. monocytogenes in a frozen processing plant and characterize the recovered isolates. A frozen vegetable processing plant was monitored before cleaning activities. A total of 78 points were sampled, including frozen vegetables. Environmental samples belonged to food-contact surfaces (FCS); and non-food-contact surfaces (n-FCS). Positive L. monocytogenes samples were found in FCS (n = 4), n-FCS (n = 9), and the final product (n = 1). A whole-genome sequencing (WGS) analysis revealed two clusters belonging to serotypes 1/2a-3a and 1/2b-3b). The genetic characterization revealed the presence of four different sequence types previously detected in the food industry. The isolate obtained from the final product was the same as one isolate found in n-FCS. A multi-virulence-locus sequence typing (MVLST) analysis showed four different virulence types (VT). The results obtained highlight the relevant role that n-FCS such as floors and drains can play in spreading L. monocytogenes contamination to the final product.
摘要：
由于与食源性爆发有关，例如与冷冻玉米有关的单核细胞增生李斯特菌血清群IVb的多国爆发，冷冻蔬菜已成为人们关注的问题。单核细胞增生李斯特菌在食品加工环境中定殖的能力是众所周知的，使细菌成为消费者的真正问题。然而,加工环境在冷冻食品污染中的重要性还没有得到很好的证实。这项研究旨在确定冷冻加工厂中单核细胞增生李斯特菌的潜在污染生态位，并表征回收的分离株。在清洁活动之前监测冷冻蔬菜加工厂。共抽取78个点,包括冷冻蔬菜。环境样品属于食物接触表面（FCS）；和非食物接触表面（n-FCS）。在FCS中发现了阳性的单核细胞增生李斯特菌样本（n=4），n-FCS（n=9），和最终产物(n=1)。全基因组测序（WGS）分析揭示了属于血清型1/2a-3a和1/2b-3b的两个簇）。遗传表征揭示了以前在食品工业中检测到的四种不同序列类型的存在。从最终产物获得的分离物与在n-FCS中发现的一种分离物相同。多毒力基因座序列分型（MVLST）分析显示了四种不同的毒力类型（VT）。获得的结果突出了n-FCS如地板和排水沟在将单核细胞增生李斯特菌污染扩散到最终产品中可以发挥的相关作用。
