Role of cyclic 3',5'-adenosine monophosphate in the development of Salmonella infection in an experiment

The changes in cAMP levels in spleen macrophages of mice infected with low-virulent and virulent Salmonella strains and the effect of propranolol on Salmonella reproduction in the spleen, and the outcome of Salmonella-induced infection have been studied. A persistent increase in cAMP levels in spleen macrophages during Salmonella infection caused by virulent Salmonella strains has been demonstrated. Low-virulent Salmonella strains failed to cause the elevation of cAMP levels in spleen macrophages. Propranolol injection to mice prevented intensive Salmonella reproduction in the spleen and diminished the animal mortality rate.     

高盐环境下鼠伤寒沙门氏菌差异糖蛋白富集及组学分析

【背景】沙门氏菌是一种革兰阴性肠道病原菌,主要依靠III型分泌系统(typeIIIsecretion systems,T3SSs)来产生与致病性相关的效应蛋白。其中沙门氏菌致病岛(Salmonellapathogenicity island,SPI)区域是关键的基因区域。高盐浓度条件可以诱导SPI-1上效应蛋白的表达。【目的】探究在高盐浓度条件下鼠伤寒沙门氏菌(SalmonellaentericaserovarTyphimurium)糖蛋白的差异表达情况,寻找有意义的效应糖蛋白。【方法】将鼠伤寒沙门氏菌在普通培养基和高盐培养基中培养,收集菌体并超声裂解,提取蛋白后,用肼偶联法富集糖蛋白并用胰酶酶解,通过二甲基标记定量及LC/MS定量蛋白质组学方法进行糖蛋白的定量,用Thermo Proteome Discoverer 2.2软件对标记蛋白进行定性及定量分析。【结果】质谱结果显示,高盐环境中,沙门氏菌有19个糖蛋白的表达发生显著改变,其中,上调蛋白10个,最为显著的是ompC基因编码的外膜孔蛋白;下调表达糖蛋白9个,最为显著的是yjgF基因编码的翻译起始抑制因子。【结论】根据定量蛋白质组...     

Uptake and replication of Salmonella enterica in Acanthamoeba rhysodes

The ability of salmonellae to become internalized and to survive and replicate in amoebae was evaluated by using three separate serovars of Salmonella enterica and five different isolates of axenic Acanthamoeba spp. In gentamicin protection assays, Salmonella enterica serovar Dublin was internalized more efficiently than Salmonella enterica serovar Enteritidis or Salmonella enterica serovar Typhimurium in all of the amoeba isolates tested. The bacteria appeared to be most efficiently internalized by Acanthamoeba rhysodes. Variations in bacterial growth conditions affected internalization efficiency, but this effect was not altered by inactivation of hilA, a key regulator in the expression of the invasion-associated Salmonella pathogenicity island 1. Microscopy of infected A. rhysodes revealed that S. enterica resided within vacuoles. Prolonged incubation resulted in a loss of intracellular bacteria associated with morphological changes and loss of amoebae. In part, these alterations were associated with hilA and the Salmonella virulence plasmid. The data show that Acanthamoeba spp. can differentiate between different serovars of salmonellae and that internalization is associated with cytotoxic effects mediated by defined Salmonella virulence loci.     

热胁迫下沙门菌细胞结构和特性变化研究进展

沙门菌(Salmonella)是一种非常重要的食源性致病菌。由于食品基质的保护作用,有些沙门菌可以抵抗热胁迫而存活下来。存活细胞往往因为热胁迫或应激而导致细胞结构、生理特性、基因及蛋白表达发生变化,并会进一步对食品原料和加工环境造成持续污染。本文主要综述沙门菌在热胁迫前后细胞形态、菌体组分、细胞壁和细胞膜结构等方面的变化,结合基因和蛋白表达改变,探讨沙门菌在热胁迫下引起的热休克反应、抗逆性和致病性分子机制。     

鼠伤寒沙门氏菌诱导昆明小鼠肠道感染模型的建立

目的:建立鼠伤寒沙门氏菌诱导昆明小鼠肠道感染模型。方法:先用5 mg/mL链霉素预处理2 d,提高小鼠对鼠伤寒沙门氏菌的敏感性,然后正常饲养1 d,攻毒前禁水禁食4 h,再分别以不同剂量灌胃攻毒2次,间隔24 h。观察小鼠临床症状,并通过组织病理切片、透射电镜和免疫组织化学的方法,分别观察小鼠肠道组织病理变化、小肠上皮细胞超微结构变化及肠道淋巴细胞增殖状况。结果:攻毒后昆明小鼠会出现昏睡、食欲不振、寒颤,甚至死亡的现象,解剖后发现小鼠肠道充血膨胀。组织病理切片显示小鼠肠粘膜受损,小肠绒毛肿胀,排列杂乱,炎性细胞浸润;透射电镜观察超微结构显示小肠上皮细胞线粒体空泡化,嵴和膜发生融合消失,粗面内质网发生扩张;免疫组织化学的方法显示肠道感染后,淋巴结肿大,T淋巴细胞大量增殖。结论:该模型对探索鼠伤寒沙门氏菌引发肠炎的发病机制、病理生理、免疫等方面作用具有重要意义,并为特异性卵黄抗体被动免疫保护效果的后续评价奠定基础。     

Comparative proteomic analysis of Salmonella tolerance to the biocide active agent triclosan

Concern has been expressed about the overuse of biocides in farm animal production and food industries. Biocide application can create selective pressures that lead to increased tolerance to one or more of these compounds and are concomitant with the emergence of cross-resistance to antibiotics. A triclosan sensitive Salmonella enterica serovar Typhimurium and the isogenic triclosan tolerant mutant were studied at the proteomic level in order to elucidate cellular mechanisms that facilitate biocide tolerance. 2-D differential fluorescent gel electrophoresis (DIGE) compared protein profiles of parent and mutant Salmonella, in the presence and absence of triclosan. Differentially expressed proteins were identified by mass spectrometry and divided into two groups: Group A describes proteins differentially expressed between susceptible and triclosan tolerant Salmonella and includes the known triclosan target FabI which contained a mutation at the triclosan target binding site. Group B identified proteins differentially expressed in response to triclosan exposure and defines a general cell defence network. Only four proteins were common to both groups highlighting the diverse range of pathways employed by Salmonella to counteract biocides. These data suggest that sub-lethal concentrations of triclosan induce discernible changes in the proteome of exposed Salmonella and provide insights into mechanisms of response and tolerance.     

Change in the biological properties of salmonellae in acquiring resistance to chloramphenicol]

Mutants of Salmonella typhimurium and Salmonella abony resistant to 40 microgram/ml of chloramphenicol were obtained during selection according to the method of Szybalski on Hottinger broth with increasing concentrations of the antibiotic. By the colony morphology the mutants were divided into 4 groups. The study of the mutant biological properties revealed changes in the growth rate characterized by elongation of the lag-phase and exponential phase, changes in the biochemical activity evident from lower fermentation rate of some carbohydrates and production of hydrogen sulphide and changes in some amino acid dependence. Increased cross resistance to tetracycline and benzylpenicillin and decreased resistance to kanamycin were noted. The LD50 of most mutants was increased as compared to that of the initial strains. Combination of several types of the changes was observed in some mutants. It is supposed that resistance to chloramphenicol in the mutants is due to mutations in several genes. Some of such genes had pleuotropic effect because of the changes in the structure of the ribosome 50S subunits.     

The biological properties of Salmonella strains isolated from adult patients at different seasons of the year]

Biological properties of Salmonella strains, isolated in different seasons from patients with the corresponding disease of moderate severity, were compared. Their morphological, biochemical, serologic properties, sensitivity to antibiotics, capacity for synthesizing O-antigen, as well as their virulence for experimental animals, have been studied. Seasonal changes in the virulence of Salmonella strains have been established: the strains isolated in autumn have proved to be more virulent than those isolated in winter. In winter the isolation rate of Salmonella strains resistant to the therapeutic doses of antibiotics is significantly higher than in other seasons. In spring and summer Salmonella O-antigen is synthesized more intensively.     

Salmonella's sensor for host defense molecules

The bacterial pathogen Salmonella typhimurium resides within phagosomes in host cells and is able to deflect the host immune response. In this issue of Cell, Bader et al. (2005) decipher an elegant mechanism by which the PhoQ sensor kinase of Salmonella is switched on by host cationic antimicrobial peptides, leading to changes in gene expression that enable Salmonella to combat the host immune response.     

The role of EF-Tu and other translation components in determining translocation step size

The two EF-Tu encoding genes, tufA and tufB, of Salmonella typhimurium have been sequenced. Nearly all the differences from their Escherichia coli counterparts are third position changes which do not alter the encoded amino acids. Unexpectedly, most of the changes in one Salmonella tuf gene are paralleled by changes in the other tuf gene perhaps due to gene repair despite the distance separating the genes. Three mutants which cause mis-framing, have their substitutions at codon 375. Explanations for mutants which cause mis-framing are considered and the mechanism of normal reading frame maintenance discussed.     

Physiological changes of Salmonella typhimurium cells under osmotic and starvation conditions by image analysis

The effects of starvation and salinity on the physiology of Salmonella typhimurium were investigated in a microcosm study. The physiological changes were monitored by using fluorochromes dyes such as DAPI (4',6-diamidino-2-phenylindole) for evaluation of the genomic content, CTC (5-cyano-2,3-ditolyl tetrazolium chloride) for respiratory activity and syto 9 and propidium iodide for cytoplasmic membrane damages. The metabolic activity of the cellular population was assessed with the method of Kogure (direct viable count), to enumerate the substrate-responsive cells. These different staining procedures were objectively analysed by an image analysis system. This paper describes the progressive alteration of Salmonella typhimurium physiology under salinity and starvation conditions.     

抗菌肽JH-3治疗沙门氏菌感染的效果评价

【目的】沙门氏菌(Salmonella)是重要的人畜共患传染病原菌,其感染是引起世界性胃肠疾病的主要因素,全球每年大概有2 100万伤寒病例,给世界公共卫生带来严重威胁。目前抗生素滥用问题严峻,急需寻找一种抗生素的替代品。抗菌肽JH-3是本实验室分离并人工改造后具有广谱杀菌活性的小肽,以沙门氏菌标准菌株CVCC541为研究对象,在小鼠模型上评价抗菌肽JH-3治疗沙门氏菌感染的效果。【方法】在CVCC541感染BALB/c小鼠前3 d连续腹腔注射抗菌肽JH-3或环丙沙星(B3d,共计40 mg/kg)和感染后3 d连续注射JH-3或环丙沙星(P3d,共计40 mg/kg)进行治疗。【结果】发现环丙沙星预防组效果最佳,抗菌肽JH-3的预防组(B3d)效果较好,可显著保护小鼠免受致死剂量CVCC541的攻击,小鼠存活率高达100%,临床症状评分、血液和脏器荷菌数降低,小肠段病理变化减轻,效果与环丙沙星治疗组相当;而感染3 d后JH-3治疗效果较差,临床症状评分、脏器荷菌量以及小肠病理变化均显著高于3 d前预防组,但3 d后治疗组小鼠存活率为70%,仍明显高于单独感染组。【结论】系统评价了抗菌肽JH-3不同给药时间对沙门氏菌感染的治疗效果,预防性给药方式的抗菌作用最佳,与环丙沙星治疗效果相当,为新型抗菌药物的研究提供参考。     

The role of IgM in paratyphoid immunity

The authors analyze the results of studies on the effect produced by the immunization of calves with paratyphoid vaccine on the production of agglutinins, changes in the blood serum immunoglobulin levels, and the specificity of IgM to Salmonella dublin and Salmonella typhimurium antigens. The highest level of agglutinins to paratyphoid antigens in the blood sera of the immunized calves was registered on days 14-21 after immunization, changes in the levels of different immunoglobulin classes being insignificant. The agglutination test and the enzyme immunoassay have revealed that antibodies to S. dublin anb S. typhimurium antigens belong to IgM.     

Comparison of Salmonella enterica serovar Typhimurium LT2 and non-LT2 salmonella genomic sequences, and genotyping of salmonellae by using PCR

Genes of Salmonella enterica serovar Typhimurium LT2 expected to be specifically present in Salmonella were selected using the Basic Local Alignment Search Tool (BLAST) program. The 152 selected genes were compared with 11 genomic sequences of Salmonella serovars, including Salmonella enterica subsp. I and IIIb and Salmonella bongori (V), and were clustered into 17 groups by their comparison patterns. A total of 38 primer pairs were constructed to represent each of the 17 groups, and PCR was performed with various Salmonella subspecies including Salmonella enterica subsp. I, II, IIIa, IIIb, IV, VI, and V to evaluate a comprehensive DNA-based scheme for identification of Salmonella subspecies and the major disease-causing Salmonella serovars. Analysis of PCR results showed that Salmonella enterica subsp. I was critically divided from other subspecies, and Salmonella strains belonging to S. enterica subsp. I were clustered based on their serovars. In addition, genotypic relationships within S. enterica subsp. I by PCR results were investigated. Also, Salmonella signature genes, Salmonella enterica serovar Typhimurium signature genes, and Salmonella enterica subsp. I signature genes were demonstrated based on their PCR results. The described PCR method suggests a rapid and convenient method for identification of Salmonella serovars that can be used by nonspecialized laboratories. Genome sequence comparison can be a useful tool in epidemiologic and taxonomic studies of Salmonella.     

实验猴主要细菌性感染疾病的病理特点分析

目的通过对实验猴细菌性感染疾病脏器病理改变的观察和分析,完善实验猴病理检测资料,为实验动物病理检测标准的制定提供依据。方法选取86例实验猴按5种必检细菌性感染疾病（沙门菌病;志贺菌病;结核杆菌病;小肠结肠炎耶尔森菌病;空肠弯曲菌病）病原种类分组,对脏器标本进行病理剖检,HE染色观察记录病变,建立实验猴必检细菌性疾病病理检测资料。结果病理检测结果显示：沙门菌病表现为伤寒肉芽肿,结核杆菌病表现为结核肉芽肿,小肠结肠炎耶尔森菌病表现为纵行溃疡、急性炎及化脓性肉芽肿;志贺菌病、空肠弯曲菌病表现为急性炎和表浅溃疡。结论感染5种必检细菌的实验猴分别表现出不同的病理变化,病理检测对疾病的分析诊断有重要价值,检测结果补充了实验猴细菌性疾病病理检测资料,为制定实验动物病理检测指南提供了相关依据。