Abstract：
This study investigated Listeria monocytogenes prevalence and count in 132 ready-to-eat (RTE) delicatessen samples belonging to different categories (starters with/without mayonnaise pasta/rice-based courses, meat/fish-based main courses) produced by an Italian industry. Whole Genome Sequencing characterized the isolates to map the pathogen circulation. Moreover, the growth potential of L. monocytogenes in the most contaminated product was investigated by a challenge test. L. monocytogenes was detected in 23 samples, giving an estimated prevalence of 17.4 %. Starters with mayonnaise showed a very high prevalence (56.7 %), showing the role of the sauce in the diffusion of the pathogen within the plant. A total of 49 isolates were obtained; they belonged to two different serogroups, IIb and IIa, and were related to two clonal complexes (CCs) and sequence types (STs) (CC288-ST330 and CC121-ST717), suggesting the possible persistence and circulation of the pathogen within the plant. The results of the challenge test showed a limited ability to grow in the selected product thanks to the presence of lactic microflora.
摘要：
这项研究调查了属于不同类别的132份即食（RTE）熟食样品中单核细胞增生李斯特菌的患病率和计数（含/不含蛋黄酱面食/米饭的开胃菜，肉类/鱼类为主的主菜)由意大利工业生产。全基因组测序表征分离物以绘制病原体循环图。此外，通过挑战测试研究了受污染最严重的产品中单核细胞增生李斯特菌的生长潜力。在23个样本中检测到单核细胞增生李斯特菌，估计患病率为17.4%。蛋黄酱初学者的患病率很高（56.7％），显示酱汁在病原体在植物内扩散中的作用。共获得49个分离株；它们属于两个不同的血清群，IIb和IIa,并与两种克隆复合物（CC）和序列类型（STs）（CC288-ST330和CC121-ST717）有关，表明病原体在植物内可能的持久性和循环。挑战测试的结果表明，由于乳酸菌群的存在，在所选产品中生长的能力有限。
