研究人员在我国发现一种高毒性李斯特菌

　　据美国食品安全新闻网消息，有研究人员在我国江苏省偏远地区发现了一种新的李斯特菌病病原体。这种病原体是该细菌物种中最具毒性的代表，被确定为该地区绵羊严重疾病的病因。

　　该种李斯特菌是由贾斯图斯·利比希大学吉森（JLU）的医学微生物研究所领导的国际研究小组发现的，JLU医学微生物研究所所长，德国感染研究中心的研究科学家Trinad Chakraborty博士表示，“这一发现凸显了国际合作的必要性。只有将资源和专业知识结合起来，我们才能迅速发现全球范围内剧毒菌株对食品安全的新威胁。”

　　在对这些细菌的基因组序列进行解码后，科学家们能够确定其高毒力的遗传基础，并确定了增强这种李斯特菌菌株引起严重败血病能力的因素。由于李斯特菌病是一种食源性感染疾病，因此鉴定此类高毒力菌株的措施非常紧急。我国江苏扬州大学人畜共患病国家重点实验室参与了此项研究，该项研究由欧盟ERA-NET PROANTILIS计划资助，同时也得到了德国感染研究中心的支持。

李斯特菌会对孕妇、胎儿、新生儿以及老年人等免疫力低下人群构成风险，感染症状包括：恶心、呕吐、腹泻等轻微类似感冒症状，严重时会出现脑膜炎以及其他致命综合症。生食品和加工食品都可能受到李斯特菌的污染，尤其是乳制品，肉类，海鲜和即食产品（如预包装的沙拉）。它可以通过水和食物传播，大家在享用各类美食的同时，要注意妥当的保存食物，尽量食用新鲜安全的食品，防止感染李斯特菌。

　　原文如下：

Researchers have detected a highly virulent new form of pathogenic Listeria monocytogenes.

　　It was identified as the cause of serious diseases in sheep in a remote area of the Chinese province Jiangsu.

　　An international research group led by the Institute of Medical Microbiology at the Justus Liebig University Giessen (JLU) said it had found the most virulent representatives of this bacterial species to date. The work was published in the journal Nature Communications.

　　In people the bacterium Listeria monocytogenes can cause an infection known as listeriosis. Contaminated food is a frequent source of the infections. Raw and processed foods can be contaminated, especially dairy products, meat, seafood and ready-to-eat products such as pre-packaged salads. Elderly people, those with a weakened immune system and pregnant women are particularly at risk of serious infections and life-threatening complications.

　　Listeria virulence

　　Professor Trinad Chakraborty, director of the Institute of Medical Microbiology at the JLU and research scientist at the German Center for Infection Research (DZIF), said the finding highlights the need for international collaboration

　　“Only by combining resources and expertise can we rapidly identify newly emerging threats to food safety from highly virulent strains worldwide,” according to the professor.

　　After decoding the genome sequence of these bacteria, scientists were able to determine the genetic basis for hypervirulence and identify the factors that enhance the ability of this Listeria strain to cause severe septic diseases.

　　“These isolates are unique in the sense that they combine the virulence characteristics of various highly pathogenic Listeria species that infect animals or humans into a single strain. Since listeriosis is a foodborne infection, measures to identify such highly virulent strains are extremely urgent,” said Chakraborty.

　　Examining the isolates

　　The foodborne pathogen Listeria monocytogenes has four evolutionarily distinct lineages. The team characterized isolates from severe ovine listeriosis outbreaks that represent a hybrid sub-lineage of the major lineage II (HSL-II) and serotype 4h. HSL-II isolates share core virulence factors found in isolates of other highly virulent Listeria monocytogenes lineages I and II, implying an association with human cases of listeriosis.

　　Isolates harbored the Listeria monocytogenes Pathogenicity Island (LIPI)-1 and a truncated LIPI-2 locus, encoding sphingomyelinase (SmcL), a virulence factor required for invasion and bacterial translocation from the gut, and other non-contiguous chromosomal segments from another pathogenic species, Listeria ivanovii. HSL-II isolates exhibit a unique wall teichoic acid (WTA) structure essential for resistance to antimicrobial peptides, bacterial invasion, and virulence.

　　Researchers studied isolates obtained during five years from different sources that harbor distinct genes from the species Listeria ivanovii. Isolates came from separate listeriosis outbreaks on goat farms in 2011, 2012, and 2015, in a remote region of Jiangsu Province, China.

　　Multi-locus sequence type (MLST) analysis revealed three isolates are members of an unidentified sequence type (ST) and clonal complex (CC). The isolates have been assigned as ST626 and CC33 by the Listeria MLST Pasteur database, and are the only ones in either category.

　　Scientists from the State Key Laboratory of Zoonosis of the University of Yangzhou in Jiangsu, China, the Laboratory of Food Microbiology of the Swiss Federal Institute of Technology (ETH) Zurich, Switzerland, and JLU, Germany were involved in the study.

　　Work at the JLU was funded by the EU ERA-NET PROANTILIS program. The study was also supported by the German Center for Infection Research.

　　In April 2018, a new bacterial species was described by investigators from the Costa Rican Institute of Technology and WHO-collaborating center on Listeria at the Pasteur Institute. The species, called Listeria costaricensis, is non-pathogenic and was isolated from water collected at an industrial drainage area in the Costa Rican province of Alajuela, after three years of sample collection and research.