一类传染病动力学时滞模型的分析

研究了一类传染病动力学模型,用摄动理论讨论了相应的非线性时滞问题,得到了被传染病感染的人群数与健康人群数比例的变化规律的渐近表达式,从而揭示了传染病的潜伏期和传染期对疾病传播的影响和作用.本文的研究为解决这一类非线性时滞模型提供了一种有效的方法.     

Epidemic modelling: Aspects where stochasticity matters

Epidemic models are always simplifications of real world epidemics. Which real world features to include, and which simplifications to make, depend both on the disease of interest and on the purpose of the modelling. In the present paper we discuss some such purposes for which a stochastic model is preferable to a deterministic counterpart. The two main examples illustrate the importance of allowing the infectious and latent periods to be random when focus lies on the probability of a large epidemic outbreak and/or on the initial speed, or growth rate, of the epidemic. A consequence of the latter is that estimation of the basic reproduction number R₀ is sensitive to assumptions about the distributions of the infectious and latent periods when using data from the early stages of an outbreak, which we illustrate with data from the H1N1 influenza A pandemic. Some further examples are also discussed as are some practical consequences related to these stochastic aspects.     

具有潜伏期的无免疫型传染病动力学模型的分析

研究了一类具有潜伏期的无免疫型传染病动力学模型,用摄动理论讨论分析了相应的非线性系统,得到了不同群体生存变化的渐近表达式,从而揭示了各种作用对不同群体生存影响的规律.本文的研究为解决一些类型的非线性模型提供了一种有效的方法.     

具潜伏期的无免疫型传染病动力学的微分模型

对具潜伏期的无免疫型传染病进行讨论,给出一个常微分模型和一个偏微分模型．     

用数学模型分析非典型肺炎预防和隔离措施的有效性

利用时滞常微分方程建立数学模型,研究在无任何预防和隔离措施的假想情况下非典型肺炎传染和发展的终极状态．通过对模型的讨论发现,在无任何预防和隔离措施的情况下,当非典疫情自生自灭以后,感染非典型肺炎的总人数占总人口的比例z主要取决于基本传染数R,即每个“非典”患者在其整个病程中的平均传染人数．根据有关报道[3,4],非典型肺炎的基本传染数R在2．2至3．6之间．根据我们的模型分析,当R=2．2时,z值可达85％左右,而当R=3．6时,z值可达97％左右．而事实上由于采取了预防和隔离措施,以北京市为例,感染非典型肺炎的总人数只有几千人,不到其总人口的千分之一．这充分说明了有关非典的预防和隔离措施的有效性．     

新形势下的传染病医院医疗应急后勤保障工作

传染病因其不可预测性和突发性,已经成为人类生存的大敌。随着气候的变化和环境的破坏,新老传染病（SARS、甲型H1N1流感、禽流感、TB等）相继出现及复燃,人民的健康不时受到威胁,传染病医院肩负着防治疾病的重任并面临巨大挑战。因此如何做好医疗应急后勤保障工作是当今新形势下传染病医院工作的重中之重。     

Network-based analysis of stochastic SIR epidemic models with random and proportionate mixing

In this paper, we outline the theory of epidemic percolation networks and their use in the analysis of stochastic susceptible-infectious-removed (SIR) epidemic models on undirected contact networks. We then show how the same theory can be used to analyze stochastic SIR models with random and proportionate mixing. The epidemic percolation networks for these models are purely directed because undirected edges disappear in the limit of a large population. In a series of simulations, we show that epidemic percolation networks accurately predict the mean outbreak size and probability and final size of an epidemic for a variety of epidemic models in homogeneous and heterogeneous populations. Finally, we show that epidemic percolation networks can be used to re-derive classical results from several different areas of infectious disease epidemiology. In an Appendix, we show that an epidemic percolation network can be defined for any time-homogeneous stochastic SIR model in a closed population and prove that the distribution of outbreak sizes given the infection of any given node in the SIR model is identical to the distribution of its out-component sizes in the corresponding probability space of epidemic percolation networks. We conclude that the theory of percolation on semi-directed networks provides a very general framework for the analysis of stochastic SIR models in closed populations.     

The infectious hypoxia: occurrence and causes during Shigella infection

Hypoxia is defined as a tissue oxygenation status below physiological needs. During Shigella infection, an infectious hypoxia is induced within foci of infection. In this review, we discuss how Shigella physiology and virulence are modulated and how the main recruited immune cells, the neutrophils, adapt to this environment.     

类志贺邻单胞菌肠道感染（附8例临床分析）

本文通过对邻单胞菌肠道感染的临床分析,对其生物性状及致病性作了详细观察,结果１２株菌性状基本相同,符合邻单胞菌特征。药敏提示除丁胺卡那霉素和氟哌酸有较强的抗菌活性外,对其它抗生素均有不同程度耐药,动物实验表明,该菌具有较强致病性,提示本菌是临床感染中不可忽视的菌种。     

儿童感染性腹泻病原学研究

目的 研究儿童感染性腹泻病原学组成与流行病学特征。方法 按《临床检验操作规程》定点逐月检测0～6岁腹泻患儿大便标本中轮状病毒、痢疾杆菌、致病性大肠埃希菌（EPEC）与沙门菌,并分析病历。结果 全年共检测693份标本,检出病原326份,检出率为47.0%;轮状病毒、EPEC、痢疾杆菌及沙门菌的检出率依次为30.2%,8.4%、7.2%与1.3%;轮状病毒与细菌性病原构成比为64.1：35.9;轮状病毒以秋冬季（10、11月与次年1、2月）、水样便标本、2岁以内年龄组以及人工和混合喂养婴儿检出率较高;细菌性病原以夏秋季（6～10月）与脓血便检出率较高;痢疾菌群中以福氏菌占优势（70%）,次为宋内杆菌（28.0%）;EPEC菌型复杂,共检出11个“O”群;检出的沙门菌有4种,即阿哥纳、德尔串、鼠伤寒与肠炎血清型。结论 开展儿童感染性腹泻病原学研究能即时发现病原,并为制定防治对策提供依据。     

杆状病毒在载体疫苗中应用的研究进展

目前利用来源于哺乳动物的病毒作病毒载体介导动物和人体的免疫应答存在诸多问题,如预存免疫和高致病力重组病毒的出现等。将自然条件下宿主为非哺乳类动物的病毒发展为载体的过程中,由于杆状病毒内在的免疫刺激活性、广泛的组织趋向性及生物安全性使杆状病毒成为疫苗载体发展中的有效工具。随着分子生物学的深入发展,国内外学者应用基因工程技术对杆状病毒转移载体进行了深入研究,并取得丰富的研究成果。对杆状病毒作为转移载体在未来载体疫苗发展中的应用进行综述。     

Survey of mange mite infesting sheep in Riyadh region,Saudi Arabia

The study was performed to survey the Sarcoptic mange in sheep and the effect of infection on the local strains during a specific period in different regions of Riyadh, Saudi Arabia. A total of 1745 sheep were examined clinically and were selected from the suspected cases for laboratory investigation of skin scrapings for disease diagnosis. The examined animals included (509) Naimi, (396) Najdi, (518) Hurri, and (322) Rufidi native sheep.The results showed that the infestation rate was (12.77%) in all sheep. The highest strain was recorded (17.2%, 14.3%, 9.6%, and 8.6%), respectively. The infestation was highest in sheep over two years of age (15.2%) while it was lowest in sheep under two years of age (11.2 %). In addition, the infection rate in females was higher than in males. The prevalence of mange mites in females was (14%) compared to (11.2%) in males. The highest percentage of infestation was recorded in the head region at 67.2%, followed by that in the neck (4.4%), back (16.5%), tail (11.6%), and legs (0%).The presence of mange mites was discovered by microscopic examination of deep skin scrapings of infected animals that were identified morphologically. The infection was assured by histological investigations. This study revealed that mange mite is one of the most significant sheep health constraints in Riyadh. Therefore, proper prevention measures must be implemented to take into consideration other non-host-related risk factors.     

Identification of bacteria in culture negative and polymerase chain reaction (PCR) positive intraocular specimen from patients with infectious endopthalmitis

A novel Denaturing High-Performance Liquid Chromatography (dHPLC)-based technique allows rapid high-resolution analysis of PCR products. We show the application of this PCR/dHPLC approach for direct detection and identification of bacterium from the Eubacterial PCR amplified products of aqueous and vitreous aspirates from patients with endopthalmitis and to differentially identify the culture negative cases and initiate appropriate therapy. The aim of this study is to identify culture negative PCR positive cases by the application of PCR based DNA sequencing. A total of 116 intraocular specimens were subjected for the study. Sixty-nine different bacteria were identified using dHPLC based DNA sequencing of which predominant ones were Gram-positive bacteria and cannot be cultured by conventional methods. Forty eight different bacteria detected in this study is being reported for the first time in infectious endopthalmitis.     

剑阁县2001-2010年法定传染病流行特征及防治对策分析

目的：通过分析10年法定传染病疫情的流行趋势和三间分布特征,为制定传染病预防控制策略和措施提供依据。方法：采用描述性流行病学方法分析疫情趋势和三间分布情况,数据资料用SPSS10．0和Excel2003进行统计分析。结果：2001～2010年共报告乙、丙类传染病25种26129例,年均发病率386．89／10万,年均死亡率0．15／10万,10年间报告法定传染病以血源及性传播传染病和呼吸道传染病为主,居第1位的是血源及性传播传染病,共报告5种12453例,占53．03％;其次是呼吸道传染病,共报告5种9828例,占41．85％,近3年发病居于各类传染病首位;第三位的是肠道传染病,共报5种1149例,占4．89％。发病居前5位的传染为乙肝、肺结核、流行性腮腺炎、痢疾、麻疹,主要传染病以乙肝、肺结核为主,近年性传播疾病呈快速增长趋势。结论：血源及性传播传染病和呼吸道传染病是今后重点防控传染病。     

Effects of cycloheximide on thymidine metabolism and on DNA strand elongation in Physarum polycephalum

Treatment of Physarum polycephalum with cycloheximide during the DNA synthesis period resulted in a reduction in the incorporation of [³H]thymidine into DNA. This effect was caused by both a reduction in the specific activity of TTP and by an inhibition of progeny strand elongation within replication units. No effect of the drug on the initiation of synthesis of replication units or on the ligation of DNA fragments was detected.     

The Molecular Biology of a Bacterial Endosymbiont1

ABSTRACT. The marine ciliate Parauronema acutum harbors a group of symbiotic bacteria, termed xenosomes, which reside exclusively in the cytoplasm where they grow and divide in a remarkable synchronism with the host. When released into the ambient culture medium by gentle rupture of the protozoans, the symbionts can infect homologous as well as heterologous Parauronema stocks and, oddly, Miamiensis avidus, a distantly related marine ciliate. Xenosomes from certain Parauronema stocks can kill other marine ciliates, particularly those of the genus Uronema. Our principal aims with this host-symbiont system have been to study, at the molecular level, the nature of the interaction of the xenosome with the host, infection and the killer effect. Our most recent investigations have been directed toward establishing the phylogenetic origins of the symbionts using molecular approaches. This paper summarizes our previous work and updates our more recent studies on the association of a bacterial symbiont with its protozoan host. The reader is referred to previous reviews for more details on the subject [4, 5].     

Human antibody response to surface layer proteins in Clostridium difficile infection

Clostridium difficile is a major cause of infectious diarrhoea in hospitalised patients. Surface layer proteins (SLPs) are the most abundant surface localised proteins expressed by C. difficile. The aim of this study was to examine the humoral immune response to C. difficile SLPs and its potential role in protection from C. difficile associated diarrhoea (CDAD). Serum antibodies to SLPs from C. difficile were measured by ELISA in a cohort of 146 patients (55 patients with CDAD, 34 asymptomatic carriers, and 57 controls). No significant difference was detected in serum IgM, IgA or IgG antibody levels between cases, carriers or control groups at any of the time points tested. However, patients with recurrent episodes of C. difficile diarrhoea had significantly lower IgM-anti-SLP levels than patients with a single episode on days 1, 3, 6 and 9 (p = 0.05, p = 0.009, p = 0.02, p = 0.049). The adjusted odds ratio for recurrent diarrhoea associated with a low day 3 serum IgM anti-SLP antibody level was 24.5 (95% confidence interval; 1.6-376.3). Further studies which examine the specific anti-SLP antibody responses to the colonising strain are warranted to determine if immune responses to C. difficile SLPs play a role in protection from CDAD.