研究人員在我國發現一種高毒性李斯特菌

　　據美國食品安全新聞網消息，有研究人員在我國江蘇省偏遠地區發現了一種新的李斯特菌病病原體。這種病原體是該細菌物種中最具毒性的代表，被確定為該地區綿羊嚴重疾病的病因。

　　該種李斯特菌是由賈斯圖斯·利比希大學吉森（JLU）的醫學微生物研究所領導的國際研究小組發現的，JLU醫學微生物研究所所長，德國感染研究中心的研究科學家Trinad Chakraborty博士表示，“這一發現凸顯了國際合作的必要性。只有將資源和專業知識結合起來，我們才能迅速發現全球范圍內劇毒菌株對食品安全的新威脅。”

　　在對這些細菌的基因組序列進行解碼后，科學家們能夠確定其高毒力的遺傳基礎，并確定了增強這種李斯特菌菌株引起嚴重敗血病能力的因素。由于李斯特菌病是一種食源性感染疾病，因此鑒定此類高毒力菌株的措施非常緊急。我國江蘇揚州大學人畜共患病國家重點實驗室參與了此項研究，該項研究由歐盟ERA-NET PROANTILIS計劃資助，同時也得到了德國感染研究中心的支持。

李斯特菌會對孕婦、胎兒、新生兒以及老年人等免疫力低下人群構成風險，感染癥狀包括：惡心、嘔吐、腹瀉等輕微類似感冒癥狀，嚴重時會出現腦膜炎以及其他致命綜合癥。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，肉類，海鮮和即食產品（如預包裝的沙拉）。它可以通過水和食物傳播，大家在享用各類美食的同時，要注意妥當的保存食物，盡量食用新鮮安全的食品，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.