Comandatore Francesco, Corbella Marta, Andreoli Giuseppina, Scaltriti Erika, Aguzzi Massimo, Gaiarsa Stefano, Mariani Bianca, Morganti Marina, Bandi Claudio, Fabbi Massimo, Marone Piero, Pongolini Stefano, Sassera Davide
S.C. Microbiologia e Virologia, Fondazione IRCCS Policlinico San Matteo, Pavia, Italia.
Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, Pavia, Italy.
PLoS Curr. 2017 Jul 6;9:ecurrents.outbreaks.633fd8994e9f06f31b3494567c7e504c. doi: 10.1371/currents.outbreaks.633fd8994e9f06f31b3494567c7e504c.
Listeria monocytogenes (Lm) is a bacterium widely distributed in nature and able to contaminate food processing environments, including those of dairy products. Lm is a primary public health issue, due to the very low infectious dose and the ability to produce severe outcomes, in particular in elderly, newborns, pregnant women and immunocompromised patients.
In the period between April and July 2015, an increased number of cases of listeriosis was observed in the area of Pavia, Northern Italy. An epidemiological investigation identified a cheesemaking small organic farm as the possible origin of the outbreak. In this work we present the results of the retrospective epidemiological study that we performed using molecular biology and genomic epidemiology methods. The strains sampled from patients and those from the target farm's cheese were analyzed using PFGE and whole genome sequencing (WGS) based methods. The performed WGS based analyses included: a) in-silico MLST typing; b) SNPs calling and genetic distance evaluation; c) determination of the resistance and virulence genes profiles; d) SNPs based phylogenetic reconstruction.
Three of the patient strains and all the cheese strains resulted to belong to the same phylogenetic cluster, in Sequence Type 29. A further accurate SNPs analysis revealed that two of the three patient strains and all the cheese strains were highly similar (0.8 SNPs of average distance) and exhibited a higer distance from the third patient isolate (9.4 SNPs of average distance).
Despite the global agreement among the results of the PFGE and WGS epidemiological studies, the latter approach agree with epidemiological data in indicating that one the patient strains could have originated from a different source. This result highlights that WGS methods can allow to better.
单核细胞增生李斯特菌（Lm）是一种广泛分布于自然界的细菌，能够污染食品加工环境，包括乳制品加工环境。由于其感染剂量极低且能够导致严重后果，尤其是在老年人、新生儿、孕妇和免疫功能低下的患者中，Lm是一个主要的公共卫生问题。
2015年4月至7月期间，意大利北部帕维亚地区观察到李斯特菌病病例数量增加。一项流行病学调查确定了一家小型有机奶酪生产农场可能是此次疫情的源头。在这项工作中，我们展示了使用分子生物学和基因组流行病学方法进行的回顾性流行病学研究的结果。使用基于脉冲场凝胶电泳（PFGE）和全基因组测序（WGS）的方法对从患者身上采集的菌株以及目标农场奶酪中的菌株进行了分析。基于WGS的分析包括：a）电子MLST分型；b）单核苷酸多态性（SNP）检测和遗传距离评估；c）耐药和毒力基因谱的确定；d）基于SNP的系统发育重建。
三株患者菌株和所有奶酪菌株均属于序列型29中的同一系统发育簇。进一步精确的SNP分析表明，三株患者菌株中的两株与所有奶酪菌株高度相似（平均距离为0.8个SNP），与第三株患者分离株的距离较远（平均距离为9.4个SNP）。
尽管PFGE和WGS流行病学研究结果达成了全球共识，但后一种方法与流行病学数据一致，表明其中一株患者菌株可能来自不同的来源。这一结果凸显了WGS方法能够更好地…… （原文此处似乎不完整）
