一株宽裂解谱大肠杆菌噬菌体的分离和裂解谱的测定及电镜观察

<正>噬菌体是一类能够寄生于细菌、放线菌及蓝细菌等微生物的病毒,又被称为细菌病毒,其体积微小并可通过细菌滤器,没有完整的细胞结构,是由英国科学家Twort在培养葡萄球菌的过程中偶然发现的[1]。噬菌体有着广泛的应用前景,最引人注目的还是其能够裂解细菌的特性,可以应用于细菌病的预防和治疗。不过用噬菌体治疗作为一种新兴的方法更多地只是停留在研究方面。因为噬菌体治疗有其缺点,即噬菌体裂解细菌的作用具有严格的宿主特异性;所以能否对症下药是保证用噬菌体治疗效果的关键。     

科苑采撷

噬菌体病毒有望替代抗生素英国剑桥的科学家最近宣称,噬菌体病毒有可能替代抗生素。以前,由于人类大量使用抗生素治疗细菌感染,许多细菌通过相互交换遗传物质获得了耐抗生素药性基因。该研究所的皮卡德说:"使用噬菌体治疗比传统的抗生素会更好,因为噬菌体不会破坏正常的微生物平衡。噬菌体只是能感染细菌的病毒,目前还没有关于噬菌体感染植物、动物或人类细胞的报道。"     

噬菌体与动物细胞的相互作用

噬菌体是动物体内最丰富的生物群体。噬菌体易获得、宿主特异性强、不易产生耐药性等特点使其在治疗耐药细菌感染方面具有很大优势。随着基因工程和显微镜技术的发展，噬菌体对动物细胞的调节机制逐渐被发现。笔者综述了近年来关于噬菌体进入动物细胞的机制、噬菌体在细胞内的分布及与细胞内受体相互作用的研究进展，强调了噬菌体在协助宿主细胞杀灭细菌过程中的作用，讨论了噬菌体与动物细胞相互作用对噬菌体治疗的意义，旨在为噬菌体治疗耐药细菌的研究提供理论基础。     

噬菌体制剂的研究现状及发展前景

噬菌体制剂是利用噬菌体溶解细胞的特性而用于治疗动物的病原菌的临床感染。早在20世纪初,噬菌体治疗就取得了积极的治疗效果。目前传统抗生素治疗动物细菌感染时易产生耐药性,而噬菌体制剂则表现出许多突出的优越性。从噬菌体的生物学特性,噬菌体制剂的作用机制,以及噬菌体制剂的发展状况和应用前景等方面进行了论述。     

金黄色葡萄球菌感染的治疗新策略—噬菌体

自1915年发现噬菌体以来,因其具有独特的能力,能够感染其特定的细菌宿主而不影响其他细菌种群,噬菌体被用于治疗各种动物和人类的细菌感染。后期由于抗生素的发明,使得人们渐渐放弃了对噬菌体的研究,转向抗生素,但是近几年由于抗生素耐药现象越来越严重,尤其是“超级细菌”的出现使得人们将目光重新转向噬菌体治疗。而金黄色葡萄球菌作为除了大肠杆菌,沙门氏菌以外的第三大病原菌,在各个领域广泛引起各种疾病,深受人们重视。本文就噬菌体的发展历史,噬菌体在金黄色葡萄球菌治疗上的优缺点及治疗的可行性做一综述。     

噬菌体在防治畜禽沙门氏菌感染中的应用

噬菌体是病毒中分布最广泛和最常见的群体,具有专一性强、裂解效率高、易发现且成本低等优点。噬菌体现阶段已被用于人类食品安全卫生、动植物病原菌的控制等方面,是代替抗生素控制细菌病的重要手段。沙门氏菌是一种常见的食源性致病菌和人畜共患病原菌,感染动物机体后会引发沙门氏菌病,导致幼龄动物出现较高的感染率和死亡率。国内养殖业主要依赖抗生素防控沙门氏菌感染,但随着细菌的不断进化,沙门氏菌在不同物种之间产生了严重的耐药性。论文就噬菌体的生物学特性和作用机制及噬菌体在防控畜禽沙门氏菌感染中的应用进行综述,以期为研究和应用提供参考。     

噬菌体的生物学特性及其在畜禽健康中的应用

近年来,关于噬菌体的生物学特性及其应用研究越来越深入。噬菌体是一类能够感染细菌、真菌及放线菌等微生物,使之成为宿主并将其杀灭的病毒。作为一种杀菌剂,噬菌体的特异性强、安全性高、分布广泛,目前主要应用于提高动物产品的安全性能及改善动物和人类肠道健康等方面。本文就噬菌体的生物学特性和其在牲畜健康养殖中的应用进行总结,旨在为进一步扩大应用领域提供方向。     

噬菌体在防控畜禽细菌性感染中的应用

近年来,因持续饲喂或滥用抗生素而引起的耐药性、药物残留和食品安全等问题日益严重,尤其是多重耐药和泛耐药菌的出现严重威胁着人类的健康。因此,寻找一种安全、高效的抗生素替代品是保障动物源食品安全、提高动物健康水平,及促进社会发展的必然需求。噬菌体是一类能够侵染细菌、真菌、放线菌等微生物的病毒总称,与传统抗生素相比,噬菌体具有存在广泛、特异性强、安全和研发成本低等优势。人类关于噬菌体的研究报道由来已久,但是随着抗生素和化学抗菌药物的大量出现,噬菌体在欧美等发达国家的研究一度中断,直至20世纪80年代,由于多重耐药菌的出现,人类又重新重视噬菌体的研究,随着现代生物技术的发展,噬菌体已广泛应用到人类疫病防控、动植物病原菌清除及保障食品安全等方面,已成为人类对抗细菌性感染的利器。作者简述了噬菌体生物学特性、噬菌体疗法优缺点,以及防控猪、鸡的大肠杆菌、沙门氏菌、弯曲杆菌等常见细菌性感染方面的研究,以期为动物生产应用提供理论依据。     

噬菌体在细菌耐药性传播中的作用及分子机制

细菌耐药性是威胁人类健康的全球问题,对于耐药性传播机制的研究受到广泛关注。目前已知的可以介导细菌耐药性/耐药基因水平转移的机制包括转化、接合转移和转导等,其中质粒等可转移元件在细菌耐药性传播过程中发挥的作用已经得到共识,而对于噬菌体介导的耐药性转导作用及机制关注较少。噬菌体是一种感染细菌的病毒,其在生态环境中广泛存在,其对细菌基因组的多样性和细菌的进化发挥了重要作用。本文综述了噬菌体的类型、前噬菌体分布、噬菌体与耐药基因的共存现象、噬菌体介导的耐药基因转移证据及其分子机制、噬菌体对肠道菌群的影响等方面,指出有必要重新认识噬菌体对于细菌耐药性发展的重要性,并对噬菌体/耐药性的未来研究方向进行了展望。     

噬菌体在防控畜禽细菌性感染中的应用

近年来,因持续饲喂或滥用抗生素而引起的耐药性、药物残留和食品安全等问题日益严重,尤其是多重耐药和泛耐药菌的出现严重威胁着人类的健康。因此,寻找一种安全、高效的抗生素替代品是保障动物源食品安全、提高动物健康水平,及促进社会发展的必然需求。噬菌体是一类能够侵染细菌、真菌、放线菌等微生物的病毒总称,与传统抗生素相比,噬菌体具有存在广泛、特异性强、安全和研发成本低等优势。人类关于噬菌体的研究报道由来已久,但是随着抗生素和化学抗菌药物的大量出现,噬菌体在欧美等发达国家的研究一度中断,直至20世纪80年代,由于多重耐药菌的出现,人类又重新重视噬菌体的研究,随着现代生物技术的发展,噬菌体已广泛应用到人类疫病防控、动植物病原菌清除及保障食品安全等方面,已成为人类对抗细菌性感染的利器。作者简述了噬菌体生物学特性、噬菌体疗法优缺点,以及防控猪、鸡的大肠杆菌、沙门氏菌、弯曲杆菌等常见细菌性感染方面的研究,以期为动物生产应用提供理论依据。     

噬菌体展示系统的构建及其在疾病防控领域应用研究进展

噬菌体展示技术作为目前应用广泛的展示抗体技术,逐渐成为生产基因工程抗体的重要工具。噬菌体展示技术是以噬菌体或噬菌粒为载体,通过将外源多肽基因整合到噬菌体基因中,以融合表达的形式将外源蛋白展示在噬菌体表面的分子生物学技术。近年来,噬菌体展示技术在抗体筛选领域的应用越来越广泛,与传统制备抗体的方法相比,噬菌体展示技术具有通量高、成本低、操作简单等特点,且通过该技术筛选得到的抗体不仅可在标签蛋白的辅助下进行选择和纯化,还可通过基因测序的方法得到单链抗体的完整基因序列。笔者首先对噬菌体抗体库进行分类,根据抗体的来源将噬菌体抗体库分为天然抗体库和免疫抗体库,通过免疫动物制备的抗体文库的特异性、抗体阳性率明显高于天然抗体文库;其次简述了噬菌体抗体库的构建流程,其中噬菌体表达载体的选择是展示技术的关键,整合了噬菌粒基因的辅助噬菌体侵染其特异性菌株,从而通过抗生素平板对该系统进行选择性筛选;最后讨论了噬菌体展示技术在疾病防控领域应用的研究进展,抗体的首次人源化使同源性抗体在临床上应用成为可能,后续用于预防和治疗病毒性疾病的动物同源性抗体的研发进一步证明了噬菌体展示技术用于生产诊断或潜在治疗试剂的能力。该综述主要聚焦于噬菌体展示系统的构建及其在疾病防控领域的应用,以期对后续通过噬菌体展示技术筛选单链抗体的应用提供指导。     

Phage Types of Salmonella enterica ssp. enterica serovar Typhimurium Isolated from Production Animals and Humans i Denmark

S. Typhimurium is one of the 2 most common salmonella serotypes causing human salmonellosis in Denmark. In order to illustrate the significance of different production animals as a source of infection, 1461 isolates were characterized by phage typing. The isolates originated from human patients and from cattle, pigs and poultry. By phage typing the isolates could be separated in 35 different phage types. Five types (10, 12, 66, 110 and 135) predominated and comprised 78.8% of the isolates. In humans, 57.3% of the isolates were phage type 12. This phage type was also predominant in pig herds and, to a lesser degree, in cattle. Phage types 110, 120, 135 and 193 constituted 86.5% of the poultry isolates while these phage types only made up 12.9% of the human isolates. The investigation showed that pigs are probably a major source of S. Typhimurium infection in humans in Denmark today.     

Isolation,Identification and Characterization Analysis of Broad-spectrum Escherichia coli O157∶H7 CVCC4050 Phage vB_EcoM_GXBP08

【Objective】 This study was aimed to explore the biological characteristics and genome characteristics of broad-spectrum Escherichia coli O157∶H7 phage.【Method】 The broad-spectrum Escherichia coli O157∶H7 lytic phage was seperated from a swine farm sewage in Nanning of Guangxi using the double-layer agar culture method.The host range and the corresponding titers of phage were determined through the methods of spot tests and plaque tests.The methods of transmission electron microscope observation,determination of the best multiplicity of infection in the plural,one-step growth curve drawing,thermal sensitivity and pH stability evaluation,sterilization experiment and the whole genome sequencing were used to analyze the morphological features,biological characteristics and the whole genomic characteristics of phage.【Result】 A broad-spectrum lytic phage against Escherichia coli O157∶H7 was successfully isolated and purified which was named as vB_EcoM_GXBP08.Phage vB_EcoM_GXBP08 could lyse 14 Escherichia coli strains with high efficiency,and the phage titers could reach 10⁹ to 10¹⁰ PFU/mL.Using Escherichia coli O157∶H7 CVCC4050 as host bacteria,the optimal multiplicity of infection (MOI) of phage vB_EcoM_GXBP08 was 1.One-step growth curve indicated that the latent period of vB_EcoM_GXBP08 was 20 min,the outbreak period was 50 min,and the outbreak quantity was 154 PFU/cell. The tolerable temperature range of phage vB_EcoM_GXBP08 was 30 to 70 ℃,and it could maintain activity at pH 4.0 to pH 10.0.The results of bactericidal experiment against CVCC4050 showed that phage vB_EcoM_GXBP08 had good germicidal efficacy when MOI was 1.According to transmission electron microscope observation and the whole genome analysis,phage vB_EcoM_GXBP08 belonged to Caudovirales order,Myoviridae family,T4-like Phagus,which had a genome consisting of 108 114 bp with a GC content of 36.23%.Phage vB_EcoM_GXBP08 genome harbored 8 CDS associated with lysis proteins and lacked virulence genes and drug resistance genes associated with antibiotic resistance,toxins and virulence factors.【Conclusion】 Phage vB_EcoM_GXBP08 had a broad host range,high titer,good thermal stability and acid-base stability,and a strong bactericidal effect in liquid medium.The results provided reference for the development of broad-spectrum phage and its application in the prevention and treatment of Escherichia coli O157∶H7 infection in food industry and breeding industry.     

噬菌体治疗制剂的研究进展

从噬菌体作为治疗制剂的前提条件、噬茵体的药物动力学特征、噬菌体可能携带的有害基因、噬菌体产物、噬菌体治疗的实例等方面综述了噬菌体作为治疗制剂的研究进展,旨在通过介绍用噬菌体替代抗生素治疗由细菌引起的感染的机理,为细菌性疾病的治疗提供新的思路和方法.     

Phage therapy in the fields of veterinary medicine: an overview

During the last years, bacteriophages have been used as valuable tool in microbiological diagnostics and basic research. Even though the potential of bacteriophages for fighting bacterial pathogens is known for a long time, the phage therapy is not used in daily routine worldwide. Due to the continuing spread of bacterial resistance to antimicrobials and an increasing awareness of the necessity to protect consumers' health, the phage therapy meanwhile has become a subject of major interest in veterinary medicine, too.This article is meant to present fields of application for phage therapy as well as current trends of development in the field of livestock animals.     

Investigation on the clinical efficacy and tolerability of a 0.4% topical stannous fluoride preparation (MedEquine Gel) for the treatment of bacterial skin infections in horses: a prospective, randomized, double-blinded, placebo-controlled clinical trial

The purpose of this prospective, double-blinded, placebo-controlled clinical trial was to investigate the efficacy and tolerability of a novel gel containing 0.4% stannous fluoride (MedEquine) for the treatment of cutaneous bacterial infections in horses. Twenty privately owned horses diagnosed with bacterial skin infections based on physical findings and cytology results were enrolled and randomly assigned to either a placebo or an active ingredient treatment group. The product was applied on affected areas daily for 4 weeks. Cytology and clinical evaluations were done by the same investigator at the beginning and at the end of the treatment. Owners scored pruritus weekly. Both owners and investigators were blinded to the allocation to the groups. At the end of the study, stannous fluoride gel treatment significantly decreased the investigator's clinical scores and owners' pruritus scores while no significant changes were detected in the vehicle treatment group. At the end of the trial, none of the horses in the stannous fluoride group required additional therapy while four of ten horses in the vehicle group required systemic therapy to resolve the infection. No adverse effects were detected in any of the groups. The gel formulation made compliance easier for owners compared to the traditional bathing regimen and allowed spot treatment, which was particularly helpful in animals with localized infections. These favourable aspects of the treatment were highlighted by the owners of the horses enrolled in the study. In conclusion, 0.4% stannous fluoride gel (MedEquine) was an effective and safe therapy for the topical management of bacterial skin infections in the horses included in the study.     

Human health aspects of antibiotic use in food animals: a review

Antibiotic use not only selects for resistance in pathogenic bacteria, but also in the commensal flora of exposed individuals. Veterinary surgeons regularly prescribe antibiotics for food animals to treat bacterial infections just as doctors do for human patients. In addition, however, animal feeds contain added antibiotics not for therapy but for economic reasons: to enhance the growth rate of these animals. Several of the antibiotics used as growth promoters are analogues of and fully cross resistant with important antibiotics used in human medicine. As a result of this high exposure to antibiotics, the prevalence of resistant bacteria in the faecal flora of these animals is high. These resistant bacteria can be directly and indirectly, via foods of animal origin, transferred to humans and either colonize the human intestinal tract or exchange their resistance genes with commensal bacteria of humans. As the intestinal flora functions as a reservoir of resistance genes for pathogenic bacteria and because many bacterial species of the intestinal flora are potential pathogens, the efficacy of antibiotic therapy in human medicine may be jeopardized.