Listeria monocytogenes as a probe of immune function.

For almost half a century, the mouse model of Listeria monocytogenes infection has been used to analyse both innate and adaptive components of immunity and to discover key immune genes. Vast accumulated knowledge about the disease in mice provides a unique framework for identifying and characterising immune molecules using a variety of experimental approaches. To illustrate the range of questions that can be addressed using modern genetics and genomics tools, the authors provide an overview of the analysis of components of immune signalling networks using the mouse model of L. monocytogenes infection.     

Influence of staphylococcal enterotoxin B (SEB) on the course of murine listeriosis

Abstract Confrontation of the immune system with bacterial superantigens leads to an initial activation of the immune system followed by a state of profound immunosuppression. To investigate the role of a superantigen in an acute infection with a facultatively intracellular bacterium, we have studied the effect of staphylococcal enterotoxin B on the course of murine listeriosis. Intraperitoneal injection of SEB led to a statistically significant growth restriction of Listeria monocytogenes in the organs of mice infected intravenously or intraperitoneally when treatment with SEB and infection with L. monocytogenes were given simultaneously or when the mice were treated two days before infection. No effect of SEB on murine listeriosis was found when SEB was given more than two days before infection or one or more days after infection. We conclude that initial immunostimulation by SEB which is indicated by a massive liberation of all interleukins measured (IL1α, IL6, TNFα, IL2, IFNγ, IL4) is responsible for the growth restriction of L. monocytogenes in the organs of treated mice. Apoptosis of Vβ8 positive T cells which was accompanied by a 30% reduction of these cells at day 7 after treatment seems to be totally compensated.     

Eucalyptus urograndis stem proteome is responsive to short-term cold stress

Eucalyptus urograndis is a hybrid eucalyptus of major economic importance to the Brazilian pulp and paper industry. Although widely used in forest nurseries around the country, little is known about the biochemical changes imposed by environmental stress in this species. In this study, we evaluated the changes in the stem proteome after short-term stimulation by exposure to low temperature. Using two-dimensional gel electrophoresis coupled to high-resolution mass spectrometry-based protein identification, 12 proteins were found to be differentially regulated and successfully identified after stringent database searches against a protein database from a closely related species (Eucalyptus grandis). The identification of these proteins indicated that the E. urograndis stem proteome responded quickly to low temperature, mostly by down-regulating specific proteins involved in energy metabolism, protein synthesis and signaling. The results of this study represent the first step in understanding the molecular and biochemical responses of E. urograndis to thermal stress.     

棉铃虫作为单核细胞增生李斯特菌感染模型的初步研究

研究单核细胞增生李斯特菌(Listeria monocytogenes,简称Lm)对棉铃虫(Helicoverpa armigera)的致病性,探讨棉铃虫作为Lm感染模型的可行性。用野生株EGDe(中毒)、PrfA缺失株(EGDeΔprfA,弱毒)和PrfA组成型高表达株(EGDeΔprfA+pERL3-prfA~*,高毒)腹腔微量注射4龄棉铃虫幼虫,计算半数致死量(LD_(50))和虫体的载菌量,同时观测棉铃虫中肠细胞的病理变化以及血细胞包囊作用和数目。实验结果显示:①EGDe、EGDeΔprfA和EGDeΔprfA+pERL3-prfA~*的LD_(50)分别为2.56×10~3 cfu/mL、1.98×10~6 cfu/mL和6.63×10~2 cfu/mL。②感染Lm后,EGDe和EGDeΔprfA+pERL3-prfA~*在棉铃虫体内各部分的活菌数均有所上升,而EGDeΔprfA却显著下降。③中肠病理切片显示,Lm对棉铃虫幼虫中肠细胞的损伤程度与菌株的毒性高低正相关,并且随时间延长差异更为明显。④EGDeΔprfA+pERL3-prfA~*对棉铃虫血细胞的包囊作用的抑制作用最强,而EGDeΔprfA基本无抑制作用。⑤感染Lm后,棉铃虫的血细胞数量先急剧上升随后减少。72 h时,感染EGDe、EGDeΔprfA和EGDeΔprfA+pERL3-prfA~*的血细胞减少量分别为45%、27%和71%。结果表明,Lm不仅能成功侵染棉铃虫幼虫并致其死亡,且其半数致死量、其对棉铃虫中肠细胞的损伤程度以及对血细胞包囊作用和数量的影响等均与细菌毒力高低有较好的关联性,表明棉铃虫幼虫(至少是4龄棉铃虫幼虫)适合作为研究Lm致病机制的昆虫模型。     

Fungome: Annotating proteins implicated in fungal pathogenesis

Sequencing genomes of different pathogenic fungi produced plethora of genetic information. This "omics" data might be of great interest to probe strain diversity, identify virulence factors and complementary genes in other fungal species, and importantly in predicting the role of proteins specific to pathogenesis in humans. We propose a component called "fungome" for those fungal proteins implicated in pathogenesis which, we believe, will allow researchers to improve the annotation of fungal proteins.     

毒力基因调控蛋白PrfA促进单核细胞增生李斯特菌生物被膜的形成

单核细胞增生李斯特菌(Listeria monocytogenes,LM)是重要的革兰氏阳性食源性致病菌,易在食品以及各种食品加工、运输和保藏设备的接触面形成生物被膜,从而具有更强的抗逆性而难以彻底清除,因此成为食品卫生安全的重要隐患.PrfA是LM毒力基因转录表达的重要调控因子,通过比较研究LM野生株(EGD和EGDe)、PrfA缺失株(EGDAprfA和EGDeAprfA)、无害李斯特菌(Listeria innocua,LI),携带组成性表达PrfA蛋白的重组无害李斯特菌(LI-pERL3-prfA*)以及重组单核细胞增生李斯特菌(EGDeΔprfA-pERL3-prfA*)生物被膜形成能力的差异,探讨LM重要的毒力调控蛋白PrfA对生物被膜形成的影响.实验结果显示:LM野生株具有较强的生物被膜形成能力,而LI形成生物被膜的能力最弱;PrfA的缺失能降低LM生物被膜的形成能力;组成性高量表达PrfA蛋白可以回复EGDeΔprfA的生物被膜形成能力,但对LI没有增强作用.以上实验结果表明:PrfA在LM生物被膜形成中具有重要的促进作用.     

Hepatocidol toxicity of Listeria species

A novel rat hepatocidal test, based on morphological changes in monolayer culture and the percentage of lactate dehydrogenase (LDH) released into the medium after exposure to culture filtrates of Listeria spp. was used to determine listerial toxicity and pathogenicity. Primary cultures of rat hepatocytes exposed to brain heart infusion (BHI) culture filtrates from ATCC strains of Listeria monocytogenes and L. ivanovii, released 91-92% and 95% of LDH after 3 h and 18.5 h, respectively. Cultured monolayers changed from normal hepatocytes into nonviable round forms. Brain heart infusion broth and BHI culture filtrates of other Listeria spp. were nontoxic to hepatocytes. The rat hepatocidal test is a quantitative and rapid system for studying listerial toxicity and pathogenicity.     

Bacteriocin production ofLeuconostoc carnosum LA54A at different combinations of pH and temperature

Summary Leuconostoc carnosum LA54A produces a bacteriocin which is active againstListeria monocytogenes andListeria innocua. The ability ofLc. carnosum to produce the bacteriocin at various combinations of the growth parameters pH and temperature was analyzed. In the case of this strain bacteriocin production seems to be coupled to growth rate. This fact enables the prediction ifLc. carnosum can produce the bacteriocin at a given set of growth parameters, simply by predicting the growth rate of this organism. In addition we have analyzed the growth behavior of the target organismL. innocua WS2258 at the same set of growth parameters.     

李斯特菌病既往中国文献报告病例分析

目的 总结中国大陆1964年至2013年报道的李斯特菌病（LD）病例,分析其临床与流行病学特征。方法 通过计算机结合手工检索我国1964年至2013年来报道李斯特菌病的文献资料,统计各李斯特菌病例的临床与流行病学信息,并进行分析。结果 总结中国大陆1964年至2013年报道的LD相关文献121篇,LD病例256例,其中非围生期病例122例,新生儿86例,围生期孕妇48例;局灶感染39例,血液系统感染103例,中枢神经系统感染103例,11例未提供感染部位信息。多为散发（252例）,仅1起爆发引起4例患者感染。青霉素耐药率18.9%,总体死亡率30.8%,新生儿组死亡率52.6%,中枢神经系统感染者死亡率39.1%。结论 李斯特菌病特别是新生儿感染者或中枢神经系统感染者病情严重,死亡率较高,应加强预防治疗。     

基于质谱技术的细胞成像研究

细胞模型可以模拟多种生命状态和疾病发展,包括单细胞、二维（2D）细胞、三维（3D）细胞微球和类器官等模型,是解析错综复杂的生物化学问题的重要工具。近年来,以细胞作为实验模型,采用质谱技术并结合形态学分析,可以从时空水平获得细胞中多种物质分子的量变和空间分布变化,包括代谢物和脂质等内源生物小分子、药物和环境污染物等外源小分子、蛋白质和多肽等內源生物大分子,为考察细胞-细胞相互作用、肿瘤细胞微环境、细胞生物信息时空异质性提供了可能。本文综述了基于质谱技术的细胞成像研究,包括细胞模型的选择和制备、细胞模型的形态学分析、质谱空间组学技术、质谱流式等技术的选择和方法发展及其相关应用。最后,提出了该领域面临的难点问题和未来的发展方向。     

A multidrug efflux transporter in Listeria monocytogenes

A chromosomal gene (mdrL) was found in Listeria monocytogenes L028, showing a high degree of similarity with multidrug efflux transporters of the major facilitator superfamily (family 2). An allele-substituted mutant of this gene failed to pump out ethidium bromide and presented lower minimal inhibitory concentrations of macrolides, cefotaxime and heavy metals. This is the first multidrug efflux pump described in Listeria.