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黏附素是具有黏附宿主细胞能力的细菌表面结构的统称,是直接介导细菌对宿主细胞黏附的物质,故又称定居因子(colonization factor)。在禽致病性大肠埃希菌侵袭宿主组织并引起宿主发病的过程中,黏附是病原菌接触和感染细胞的第一步,因此,黏附素黏附宿主上皮细胞并使宿主致病的作用机理引起了研究者的广泛关注。论文通过对禽致病性大肠埃希菌黏附素的组成成分、黏附机制、种类、分子生物学特性以及相应的黏附素受体等进行相关综述,为研究禽大肠杆菌病的发病机理及对该病进行免疫预防提供理论依据。 相似文献
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三聚体自转运黏附素(trimeric autotransporter adhesin,TAA)是近年来发现的参与猪胸膜肺炎放线杆菌(Actinobacillus pleuropneumoniae,APP)黏附宿主细胞的重要毒力因子。本研究比较了5b adh基因缺失株(△adh)与5b野生株的生物学特性及其对仔猪的致病性。结果表明,在BHI液体培养基中,△adh生长速度明显高于5b野生株;△adh在液体培养基中细菌集聚性明显减弱;仔猪感染后临床症状典型,猪肺脏病理组织切片结果表明,△adh致病性弱于野生株。本研究结果证实adh在APP黏附宿主过程中发挥重要作用,为下一步探究APP致病机制奠定基础。 相似文献
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试验对三聚体自转运黏附素(TAAs)的重要功能区第1 703～2 018氨基酸残基区域进行原核表达,并利用激光共聚焦显微镜观察重组蛋白在猪肺上皮细胞的结合部位,通过黏附抑制试验研究该蛋白的生物活性.结果显示,扩增的adh4基因片段与GenBank中相应的基因序列的同源性达100%,表达得到相对分子质量约为31 000的Adh4蛋白,该蛋白能够黏附在猪肺上皮细胞膜表面.猪肺上皮细胞经Adh4蛋白处理后,降低了APP对它的黏附能力,同时Adh4抗体可以抑制该菌对细胞的黏附,黏附菌数与其稀释度呈负相关.结果表明,Adh4蛋白可以介导APP对猪肺上皮细胞的黏附作用,进一步证明了位于N端1703～2018氨基酸残基区域是三聚体自转运黏附素蛋白的功能区,为研究胸膜肺炎放线杆菌的黏附机制奠定了基础. 相似文献
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乳酸杆菌是人和动物肠道中重要的益生菌。益生菌进入肠道后,能够黏附定植并形成黏膜生物屏障,帮助肠道抵御各种致病菌的感染,维持肠道的正常功能。乳酸杆菌的黏附是由其表面蛋白、脂磷壁酸和胞外多糖等黏附素与宿主细胞表面的受体相结合的过程。为深入研究黏附机制,本文主要对乳酸杆菌黏附肠道上皮的黏附素和受体等方面进行综述。 相似文献
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猪繁殖与呼吸综合征病毒(PRRSV)是世界范围内威胁猪健康的最主要的因素,被认为是当今养猪业中最重要的病毒病。在过去的几年中,对病毒侵入宿主细胞的研究使许多病毒受体及病毒进入调控因子被鉴定出来。然而,与这些大分子相对应的病毒组分仍不清楚,这使得合理开发新型疫苗变得很困难。该研究的主要目的是鉴定巨噬细胞上的关键性PRRSV受体—唾液酸黏附素相对应的病毒组分。为此,作者构建了可溶性的唾液酸黏附素并对其进行验证。在唾液酸依赖途径中,可溶性的唾液酸黏附素可以与PRRSV结合,并阻断PRRSV对巨噬细胞的感染,因此可以确定唾液酸黏附素是巨噬细胞上PRRSV所必需的受体。尽管唾液酸也存在于膜糖蛋白GP3、GP4和GP5中,但是只有PRRSV的M/GP5糖蛋白复合物被证实为唾液酸黏附素的配基。试验结果发现,两者之间的相互作用依赖于唾液酸黏附素结合唾液酸的能力及GP5上的唾液酸。这些研究结果不仅有利于更好的了解PRRSV的生物学特性,而且该研究结果及研究方法是开发PRRSV新型疫苗的关键。 相似文献
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为研究胸膜肺炎放线杆菌(APP)三聚体自转运黏附素(TAAs)的功能,以GenBank登录的APP血清5b型自转运黏附素基因5'端的3875bp序列设计引物,通过PCR的方法首次获得APP血清8型运黏附素N端的基因序列片段,测序结果与已知血清型的基因序列和氨基酸推导序列分别进行比对,结果表明与血清7型自转运黏附素N端同源性达到93%,氨基酸推导序列同源性达到97%;与血清5b型自转运黏附素N端同源性达到92%,氨基酸推导序列同源达到100%.经软件分析获得的序列含有与细菌的黏附、聚集和侵入密切相关的Hep_Hag基序,应用马克斯-普朗克研究所的在线分析TAAs的基序和蛋白域的软件daTAA,进行预测并证明所得序列为TAAs,并且具有完整的N段头部序列,有重要功能区具有良好的抗原性.比对的结果为寻找研究APP的定植基序和毒力因素提供了重要基础. 相似文献
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土拉弗朗西斯菌(Francisella tularensis,Ft)是一种可引起人畜共患的胞内病原菌,属于革兰氏阴性菌,具有多形性,无芽孢,无鞭毛,可感染多种类型的细胞。在体内,Ft主要感染巨噬细胞并在其中复制。为了在宿主体内建立有效感染,Ft已进化出多种策略以拮抗宿主的免疫机制,适应宿主巨噬细胞质的环境并延缓细胞凋亡。这些策略主要包括增强机体对菌体的摄取、菌体从吞噬小体中逃逸、拮抗宿主的氧化防御、抑制宿主的炎症反应和维持菌体自身的稳定等。论文主要从这些方面对Ft的致病机制研究进展进行综述,以期为该病原的研究提供参考。 相似文献
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NhhA是在对脑膜炎球菌MC58株进行全基因组测序过程中发现的膜表面蛋白质,属于三聚体自体转运黏附素家族,介导细菌黏附于宿主鼻黏膜上皮细胞。为了对NhhA在小鼠体内诱生体液免疫效果进行评价,将截去信号肽编码序列的目的基因克隆到原核表达载体pET-21b(+)上,3′端与6×His标签融合表达,用Ni柱螯合层析法纯化目的蛋白,并用脑膜炎球菌A、B、C、W135、Y群的混合免疫血清对重组目的蛋白进行免疫印迹鉴定,结果均呈阳性反应。以Al(OH)3和CpG作为NhhA的佐剂免疫Balb/c小鼠,二次免疫后采血进行ELISA检测,其血清抗体滴度高达1∶100 000。用脑膜炎球菌裂解物鉴定免疫血清的特异性,结果显示为阳性。 相似文献
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In Gram-negative bacteria, autotransporters are secreted proteins able to translocate themselves through the inner- and outer-membranes to the cell surface or to the extracellular environment. The influence of the putative outer membrane autotransporter (OmaA) protein to the persistence of Brucella suis was investigated. Sequence analyses revealed that the OmaA protein of B. suis strain 1330 consists of a signal peptide, a passenger alpha-domain, and a transporter beta-domain, which are the characteristic components of an autotransporter protein. The transporter beta-domain consists of 14 individual amphipathic beta-strands, and a 46-amino acid long alpha-helix lies upstream of the transporter domain, indicating that the B. suis OmaA is a type-I classical autotransporter. BLAST search and phylogenetic analyses revealed that the B. suis OmaA protein shares more similarities with adhesin autotransporter proteins than with protease autotransporter proteins of other bacteria. An OmaA-deficient strain (1330DeltaomaA) was generated by disrupting the DNA region encoding the passenger alpha-domain of the OmaA protein of B. suis wild type strain 1330. The omaA gene encoding the full-length OmaA protein was cloned and used to complement the OmaA-deficient strain. The OmaA-deficient strain did not differ from the wild type strain in terms of persistence in J774 macrophage cell line 24 and 48 h after inoculation, or clearance from the spleens of BALB/c mice at 1 week after intraperitoneal inoculation. These observations suggest that the function of the OmaA protein is dispensable during the acute phase of B. suis infection. However, the OmaA-deficient strain was cleared from the spleens of BALB/c mice faster than the wild type strain between the third and the ninth week after intraperitoneal inoculation, indicating that the OmaA may be important during the chronic phase of B. suis infection. Relative to the BALB/c mice injected with saline, those vaccinated with the OmaA-deficient strain exhibited 3.0-3.9log10 colony forming units protection against a challenge with B. suis strain 1330. This study is the first report correlating an autotransporter protein deficiency with persistence of B. suis in vitro and in vivo. 相似文献
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Bruno B. Chomel Henri-Jean Boulouis Edward B. Breitschwerdt Rickie W. Kasten Muriel Vayssier-Taussat Richard J. Birtles Jane E. Koehler Christoph Dehio 《Veterinary research》2009,40(2)
Bartonella spp. are facultative intracellular bacteria that cause characteristic host-restricted hemotropic infections in mammals and are typically transmitted by blood-sucking arthropods. In the mammalian reservoir, these bacteria initially infect a yet unrecognized primary niche, which seeds organisms into the blood stream leading to the establishment of a long-lasting intra-erythrocytic bacteremia as the hall-mark of infection. Bacterial type IV secretion systems, which are supra-molecular transporters ancestrally related to bacterial conjugation systems, represent crucial pathogenicity factors that have contributed to a radial expansion of the Bartonella lineage in nature by facilitating adaptation to unique mammalian hosts. On the molecular level, the type IV secretion system VirB/VirD4 is known to translocate a cocktail of different effector proteins into host cells, which subvert multiple cellular functions to the benefit of the infecting pathogen. Furthermore, bacterial adhesins mediate a critical, early step in the pathogenesis of the bartonellae by binding to extracellular matrix components of host cells, which leads to firm bacterial adhesion to the cell surface as a prerequisite for the efficient translocation of type IV secretion effector proteins. The best-studied adhesins in bartonellae are the orthologous trimeric autotransporter adhesins, BadA in Bartonella henselae and the Vomp family in Bartonella quintana. Genetic diversity and strain variability also appear to enhance the ability of bartonellae to invade not only specific reservoir hosts, but also accidental hosts, as shown for B. henselae. Bartonellae have been identified in many different blood-sucking arthropods, in which they are typically found to cause extracellular infections of the mid-gut epithelium. Adaptation to specific vectors and reservoirs seems to be a common strategy of bartonellae for transmission and host diversity. However, knowledge regarding arthropod specificity/restriction, the mode of transmission, and the bacterial factors involved in arthropod infection and transmission is still limited. 相似文献
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Mario Santoro Giovanna Hernández Magaly Caballero 《Journal of zoo and wildlife medicine》2006,37(4):549-552
Bacteriological examination of 70 nesting green turtles (Chelonia mydas) from Tortuguero National Park, Costa Rica was performed to investigate nasal and cloacal aerobic bacteria. A total of 325 bacterial isolates were obtained, including 10 Gram-negative and three Gram-positive genera. Two hundred thirty-nine were Gram-negative and 86 were Gram-positive isolates. Klebsiella pneumoniae was the most common microbe identified in turtle samples: 27/70 (38.5%) in cloacal, and 33/70 (47.1%) in nasal samples. The Enterobacteriaceae family, including Enterobacter agglomerans, E. cloacae, Escherichia coli, Klebsiella oxytoca, K. pneumoniae, and Serratia marcescens, was the largest Gram-negative group of bacteria recovered and comprised 127 of 239 (53.1%) of the Gram-negative isolates. Staphylococcus species was the largest Gram-positive bacteria group, including S. aureus, S. cromogenes, S. epidermis, and S. intermedius, and made up 63 of 86 (73.2%) of the Gram-positive isolates recovered. The results of this study demonstrate that the aerobic bacterial flora of nesting green turtles at Tortuguero National Park is composed of a very wide spectrum of bacteria, including several potential pathogens. 相似文献
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Objectives: To assess the antibiotic susceptibility of bacteria isolated from corneal ulcers in cats. Methods: A total of 92 cats with infected corneal ulcers were swabbed for bacterial culture and the antibiotic sensitivity of the isolates analysed. Results: Bacteria were isolated from 54 of 92 infected eyes with corneal ulcers and purulent discharge. A total of 59 bacterial isolates were obtained from the 54 ulcers. The ratio of Gram-positive to Gram-negative isolates was approximately 3:1. The most commonly isolated Gram-positive bacteria were Staphylococcus species (51 per cent of all isolates), while Pseudomonas aeruginosa (13.5 per cent of all isolates) was the most common Gram-negative bacteria isolated. The Gram-negative isolates demonstrated a greater incidence of antibiotic resistance than the Gram-positive ones. The most effective antibiotics against the isolates were ciprofloxacin, tobramycin and gentamicin, with erythromycin and lincomycin showing the greatest number of resistant isolates. Clinical Significance: Staphylococcus and Pseudomonas species were the most common Gram-positive and Gram-negative bacteria, respectively, isolated from feline eyes with ulcerative keratitis. The second-generation fluoroquinolone, ciprofloxacin and the aminoglycoside gentamicin were found to be highly effective against the majority of isolates. 相似文献
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Bacterial blood culture results of 292 privately owned cats presented to the Clinic for Small Animal Medicine, Ludwig Maximilian University Munich with signs of sepsis were evaluated retrospectively. Of the blood cultures, 23% were positive. In 88%, a single bacterial species was isolated. Of all bacterial isolates, 45% were Gram-positive, 43% were Gram-negative, and 12% were obligate anaerobes. The most frequently isolated bacteria were Enterobacteriaceae, obligate anaerobic species, Staphylococcus species and Streptococcus species. Of the cats with positive blood cultures, 32% were pretreated with antibiotics. Of all bacterial isolates, 77% were susceptible to enrofloxacin, 69% to chloramphenicol, 67% to gentamicin, and 64% to amoxycillin clavulanic acid. Only enrofloxacin reached an in vitro efficacy of more than 70% against Gram-positive and more than 74% against Gram-negative bacteria. 相似文献
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In this paper a simple adhesion assay suitable for the assessment of bacterial adhesion to both canine and feline corneocytes is described. Using this assay Staphylococcus intermedius, Staphylococcus aureus and Staphylococcus chromogenes were shown to adhere well to both canine and feline corneocytes. The numbers of adherent bacteria were, however, generally lower for feline corneocytes. Both Staphylococcus hominis and a Micrococcus species adhered poorly to canine and feline corneocytes. This is the first report documenting bacterial adhesion to feline corneocytes. 相似文献
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为了探讨载铜蒙脱石(MMT-Cu)对大肠杆菌K88和猪霍乱沙门菌的黏附作用,试验采用Ca-co-2细胞培养模型,观察被标记的大肠杆菌K88、猪霍乱沙门菌对载铜蒙脱石的黏附作用;并在培养液中加入载铜蒙脱石,计算其对细菌黏附的阻断率,测定胞内乳酸脱氢酶(LDH)的释放情况。结果表明:测试菌与Caco-2细胞的黏附率分别为13.23%和10.78%;载铜蒙脱石对病原菌黏附Caco-2细胞均有不同程度的阻断作用,对大肠杆菌K88、猪霍乱沙门菌的阻断率分别为67.38%和60.45%,并能极显著降低LDH的释放(P<0.01)。说明载铜蒙脱石可有效阻断病原菌黏附,从而防治肠道细菌感染和细菌移位,可作为一种消化道黏膜保护剂。 相似文献