病原体致病性和毒力的现代概念

微生物致病性和毒力的传统概念不能反映病原体与宿主相互作用的复杂关系。本文介绍一种损伤－应答分类法,将致病性的现代概念。     

病原体毒力的进化

病原体毒力的进化是进化生物学和传染病预防控制中的重要课题。最具有进化优势的病原体应该是能够最大限度传播自身,对宿主造成的危害越小,越有利于病原体的长期传播。但根据“交易模型”,病原体在具有传播能力的同时,不可避免地造成宿主适应性的降低。由这一模型预测的病原体毒力进化,会在传播率最大和对宿主影响最小之间取得平衡,以便病原体的基本繁殖率最大化。本文介绍了近年来对这一模型的研究结果、其可能的使用意义和存在的争议,以及进一步完善模型的必要性．     

疫苗类型与病原体毒力演变的关系

Gandon通过建立病原体系力演变数学模型,研究有缺陷疫苗对病原体毒力演变的影响。发现4种类型疫苗中抗生长疫苗,抗毒疫苗使用后会导致原体演变为高毒力株,抗感染疫苗使用后可使原体演变为低毒力株,抗传播疫苗对病原体毒力影响较小,这一发现有助于疫苗的研究和应用。     

女性生殖道感染常见病原体及药敏研究进展

生殖道感染在妇科疾病中发病率较高,可造成不孕、异位妊娠、胎膜早破、早产等不良后果。引起女性生殖道感染的病原体种类较多,且由于临床不合理用药现象日趋严重,各种病原体对抗菌药物的耐药性逐年上升。本文对引起女性生殖道感染的常见病原体种类、病原体对女性生殖健康的影响及药敏试验研究进展进行了综述。了解各病原体特点,开展各种病原体对药物敏感性试验,可减少女性生殖道感染的复发率,提高治愈率,为改善女性生活质量与促进生殖健康提供帮助。     

嗜肺军团菌毒力基因、致病性及实验诊断研究进展

嗜肺军团菌是引起军团菌肺炎的重要病原体,关于军团菌感染的致病机制目前尚不十分清楚。近来研究发现,军团菌的致病性与其毒力因子和铁代谢等相关,本文对嗜肺军团菌的毒力因子及其作用。致病机制和实验室诊断方法研究进展作一综述。     

莱姆病的实验诊断

本文简要地说明一些可供莱姆病实验诊断的方法及其应用价值,包括培养分离和组织中的直接检测、免疫学方法和分子生物学方法,并对各种方法的应用价值进行了评估。     

复合性感染的复数菌药敏实验分析

从检材中培养出细菌是确立感 (传 )染性疾病诊断和治疗的基本依据 ,单一需氧菌的培养方法易遗漏厌氧菌和缺壁细菌 ,不能概括致病原因菌的全貌 [1 ] ,使多种类细菌的混合性感染不能准确诊断和治疗。我室于 1999年接待了用常规方法仅培养部分需氧菌或未培养出细菌的检材 3例 (血 1例、腹水 1例、尿 1例 ) ,同时进行需氧菌、厌氧菌及细菌 L型培养 ,检测结果报告如下 :1　材料与方法1.1　标本来源　标本来自本市医院患儿 3例 ,拟诊为“败血征”血 1例 ,诊断为“脾亢”腹水 1例 ,诊断为“膀胱炎”尿 1例。1.2　培养基1.2 .1　需氧菌 (简称 X)培…     

细鳞鲑细菌性败血症病原菌的分离鉴定及药敏实验

从21尾患病细鳞鲑Brachymystax lenok体内分离到1株致病菌,经分离培养、生化鉴定、16S r DNA序列分析及人工感染实验,确定该病原菌为嗜水气单胞菌Aeromonas hydrophila。采用26种抗菌药物进行药敏分析,结果发现,分离菌株对氨苄西林、头孢呋辛钠、卡那霉素等10种抗生素敏感;对羧苄西林、头孢噻肟、环丙沙星、新霉素等9种抗生素中度敏感;对大观霉素、诺氟沙星、四环素等7种药物耐受,为细鳞鲑细菌性疾病的防控提供了重要依据。     

烟曲霉抗原及实验诊断的研究进展

烟曲霉是多种医源性因素导致的机会性,严重深部真菌感染的主要病原菌,烟曲霉病的早期诊断及防治是亟待解决的问题,目前,研究烟曲霉特异性抗原是发展早期诊断曲霉病方法的基础。     

嗜水气单胞菌菌蜕的制备及其对银鲫的口服免疫

菌蜕系统是一个自身具有佐剂性质的新型疫苗体系,不含细胞质内容物但具有细菌的完整表面抗原结构,可诱导机体的体液、细胞免疫应答及增强黏膜免疫反应.本研究通过将带有裂解基因E的质粒pElysis转化至嗜水气单胞菌J-1株中,对Ah J-1(pElysis)进行温度诱导,温度从28℃升至42℃,每隔15min检测菌液的OD600值,测定其溶菌动力学,并做无菌检验,用扫描电镜观察裂解后的细菌形态,研究其作为口服疫苗对银鲫的效果.结果显示,通过温度诱导,嗜水气单胞菌J-1(pElysis)OD值在诱导30min后开始持续下降,75min时开始趋于平稳,到120min溶菌效率达99.99%,诱导16h后进行无菌检验,证实其无活菌.扫描电镜观察绝大部分菌体经诱导后形成菌蜕,细胞两端有溶菌通道.动物试验表明,用菌蜕口服免疫的银鲫,在第5周产生较高的凝集抗体,达到27,并能维持2周;而甲醛灭活苗组为26,维持时间仅一周;生理盐水对照组效价仅2.攻击试验表明,菌蜕疫苗组和甲醛灭活疫苗组对嗜水气单胞菌强毒株J.1的攻击均有保护作用,其相对保护率分别为16/20(78.95%)和12/20(57.9%),显示菌蜕疫苗比普通灭活疫苗能更有效地激活机体的免疫保护.     

Effect of oral immunization with Aeromonas hydrophila ghosts on protection against experimental fish infection

Aims:  To investigate whether oral immunization with Aeromonas hydrophila ghosts (AHG) vaccine can elicit mucosal and systemic immune responses of Carp ( Carassius auratus gibelio ) compared to conventional formalin-killed bacteria (FKC).
Methods and Results:  Fish were fed diets coated with AHG, FKC or phosphate buffered saline (PBS) alone, after immunization, more antigen-specific antibody was significantly detected in serum and intestinal mucus in AHG group than FKC group and PBS group. In addition, after challenged with the parent strain J-1, the survival of bacterial ghost-vaccinated fish was higher than PBS group and FKC group, the relative per cent survival (RPS) being 76·8%, 58·9%, respectively.
Conclusions:  Oral immunization with A. hydrophila ghosts can elicit systemic and mucosal adaptive immune responses and has higher potential to induce protective adaptive immunity than normal vaccine.
Significance and Impact of the Study:  Oral immunization with bacterial ghosts is a promising new solution with potential application to prevent diseases in fish.     

Isolation and characterization of bacteriophage PM3 from Aeromonas hydrophila the bacterial receptor for which is the monopolar flagellum

PM3 is an Aeromonas-specific bacteriophage which was isolated and characterized on A. hydrophila strain TF7. Spontaneous mutants resistant to PM3 were non-motile having lost their characteristic monopolar flagellum. In addition, purified flagella inactivated PM3. PM3 is the first filamentous bacteriophage isolated on Aeromonas, the adsorption site for which is the monopolar flagellum.     

Properties of membranous phospholipase C from WRK1 cell: sensitivity to guanylnucleotides and bacterial toxins

As previously described, WRK₁ plasma membrane possesses a vasopressin-sensitive phospholipase C [G. Guillon et al., FEBS Lett. 196, 155–159]. In the present study, we examined the sensitivity of this enzyme to guanylnucleotides. GTPγS induced a time- and dose-dependent stimulation of Ins(1,4,5)P₃ and Ins(1,4)P₂ accumulation. No accumulation of InsP₁, Ins(1,3,4)P₃ or Ins(1,3,4,5)P₄ occured under similar conditions. Gpp(NH)p produced the same effect but was less potent. GTP and a nonhydrolyzable analogue of ATP, App(NH)p, were without effect. Calcium also stimulated the phospholipase C activity in a time- and dose-dependent manner. In the absence of calcium, the activity of GTPγS was considerably reduced. Physiological calcium concentrations (between 10⁻⁸ and 10⁻⁷M), allowed maximal GTPγS stimulation of phospholipase C activity. In this system, the presence of vasopressin alone did not generate inositol phosphate accumulation. However, this hormone: (i) reduced the lag-time observed during GTPγS stimulation, (ii) increased the sensitivity of phospholipase C to GTPγS, and (iii) did not modify the stimulation of phospholipase C induced by maximal doses of GTPγS. Unlike sodium fluoride, GTPγS elicited an irreversible activation of phospholipace C. Calcium, GTPγS and sodium fluoride stimulated the phospholipase C activity via mechanisms sharing a common step, since their maximal effects were not additive. Cholera toxin treatment, known to produce complete ADP-ribosylation of ‘s’ subunits, partially reduced the basal and the maximal GTPγS-mediated stimulation of phospholipase C activity as well as that caused by vasopressin. This inhibition was not mimicked by treatment with either forskolin or pertussi toxin.     

水产品中嗜水气单胞菌耐药性研究进展

嗜水气单胞菌Aeromonas hydrophila具有广泛的致病性,是水生动物最常见的致病菌之一。由于抗生素不合理使用、质粒以及耐药基因的水平转移等因素,来自零售市场、超市和餐厅的即食海鲜产品中,均可分离出大量的嗜水气单胞菌耐药菌株及其耐药基因。因此,探明关键控制点、寻求有效缓解抗生素耐药性的防控策略至关重要。文中介绍了我国嗜水气单胞菌的耐药现状,嗜水气单胞菌的主要侵染及耐药机制,以及目前削减和防控耐药性的主要手段和策略,并对水产品耐药性研究方向和重点作出展望。     

Degradation of benzyldimethylalkylammonium chloride by Aeromonas hydrophila sp. K

AIMS: The aim of this work was to study the biodegradation of benzyldimethylalkylammonium chloride (BAC) by Aeromonas hydrophila sp. K, an organism isolated from polluted soil and capable of utilizing BAC as sole source of carbon and energy. METHODS AND RESULTS: High performance liquid chromatography and gas chromatography-mass spectrometry (GC-MS) analysis was used to study BAC degradation pathway. It was shown that during BAC biodegradation, formation of benzyldimethylamine, benzylmethylamine, benzylamine, benzaldehyde and benzoic acid occurred. Formation of benzyldimethylamine as the initial metabolite suggested that the cleavage of Calkyl-N bond occurred as the first step of BAC catabolism. Liberation of benzylmethylamine and benzylamine likely resulted from subsequent demethylation reactions, followed by deamination with formation of benzaldehyde. Benzaldehyde was rapidly converted into benzoic acid, which was further degraded. CONCLUSIONS: Aer. hydrophila sp. K is able to degrade BAC. A degradation pathway for BAC and related compounds is proposed. SIGNIFICANCE AND IMPACT OF STUDY: These findings are significant for understanding biodegradation pathways of benzyl-containing quaternary ammonium compounds.     

Analysis of the interaction of Aeromonas caviae, A. hydrophila and A. sobria with mucins

Aeromonas species are known to be involved in human gastrointestinal diseases. These organisms colonize the gastrointestinal tract. Aeromonas hydrophila, A. caviae, and A. sobria have been demonstrated microscopically to adhere to animal cell lines that express mucous receptors, but quantitative studies of adherence to mucosal components such as mucin have not been published to date. Purified bovine submaxillary gland, hog gastric mucin, and fish skin mucin were used as a model to study mucin-binding activity among A. caviae, A. hydrophila, and A. sobria strains. Our findings revealed that binding of radiolabeled and enzyme-conjugated mucins to Aeromonas cells varied depending on the labeling procedure. The highest binding was observed when the three mucin preparations were labeled with horseradish peroxidase. Binding of the various horseradish peroxidase-labeled mucins by A. caviae, A. hydrophila, and A. sobria cells is a common property among Aeromonas species isolated from human infections, diseased fish, and from environmental sources. The proportion of Aeromonas strains which bind the various horseradish peroxidase-labeled mucins was significantly higher for A. hydrophila than for A. caviae and A. sobria. Bacterial cell-surface extracts containing active mucin-binding components recognized the horseradish peroxidase-labeled mucins. The molecular masses of the mucin-binding proteins were estimated by SDS-PAGE and Western blot as follows: A. caviae strain A4812 (95 and 44 kDa); A. hydrophila strain 48748 (97, 45, 33 and 22 kDa); and A. sobria strain 48739 (95 and 43 kDa). Mucin interaction with Aeromonas cells was also studied in terms of growth in mucin-rich media. The culture conditions greatly influence the expression of A. hydrophila mucin-binding activity.     

Cloning and characterization of an extracellular temperature-labile serine protease gene from Aeromonas hydrophila

Aeromonas virulence is thought to depend on multigenic functions. The gene for an extracellular protease from Aeromonas hydrophila SO2/2 was cloned in Escherichia coli C600-1 by using pIJ860, bifunctional plasmid, as a vector. The gene encodes for a temperature-labile serine protease (P2) with a molecular mass of approx. 68 kDa which is highly inhibited by PMSF. The gene was expressed in Streptomyces lividans 1326 by transforming protoplasts with the original clone pPA2. We were also able to transfer and express the prt P2 gene in Pseudomonas putida by mating experiments. The protein P2 was secreted into the periplasms of both P. putida and E. coli C600-1 being identical in properties to one of the proteases secreted into the culture supernatant by A. hydrophila SO2/2.     

宽体金线蛭嗜水气单胞菌感染的病原检验

对河北某宽体金线蛭（Whitmania pigra Whitman）养殖场所养殖的宽体会线蛭发生的病害,进行了发病情况、临床表现、病理变化等方面的枪验。同时,择代表菌株进行了16S rRNA基因的分子鉴定,测定了16S rRNA基因序列、分析了相关细菌相应序列的同源性、构建了系统发生树。结果表明所检病例为由嗜水气单胞菌（Aeronmnas hydrophila）所引起的感染。分离后做纯培养的10株嗜水气申胞菌均为同种血清型菌株;代表菌株对健康宽体金线蛭的人工感染试验表明了相应的原发病原学意义;药敏试验结果显示,对供试37种抗菌药物中的头孢噻肟等高度敏感、对链霉素等敏感、对苯唑青霉素等耐药。