维生素C碳点对水产养殖主要病原菌的抗菌性能及其生物相容性

为了验证维生素C碳点对水生动物病原菌的抑制效率，实验采用3倍梯度稀释法检测了维生素C碳点对嗜水气单胞菌、副溶血性弧菌、灿烂弧菌、诺卡氏菌等12种常见水产病原菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)，在此基础上，测定了其对这12种水产病原菌的抑菌动力学曲线。此外，基于纳米材料可能存在的生物相容性等问题，实验采用MTT法检测了维生素C碳点对草鱼肾细胞的细胞毒性，并以斑马鱼胚胎为测试对象，测定其经维生素C碳点暴露后的胚胎毒性。结果显示，维生素C碳点对所监测的12种水产病原菌均有显著的抑制作用，MIC为20.6～61.7μg/mL，基本达到与抗生素氟苯尼考同等的抗菌作用。维生素C碳点在MIC范围内胚胎和细胞存活率可接近100%，与对照组无差异。研究表明，维生素C碳点对水产主要病原菌有良好的杀菌和抗菌效果，具有较好的生物相容性，在水产养殖细菌性病害防治上具有潜在的开发应用前景。     

盐酸多西环素和烟酸诺氟沙星联合用药的离体抗菌作用(上)

<正>为了治疗严重混合感染、扩大抗菌谱、减少耐药发生和减轻毒副反应,联合用药的方式在临床上的应用越来越多。已经有研究报道指出,将盐酸多西环素与恩诺沙星联合使用时,其抗菌作用增强。本研究通过盐酸多西环素与烟酸诺氟沙星联合用药,观察从患病黄颡鱼体内分离的爱德华菌、柱状黄杆菌和嗜水气单胞菌的体外抗菌活性,为水产用盐酸多西环素和烟酸诺氟沙星复方制剂的研制及合理配伍提供科学依据。一、材料与方法1.供试药品本研究中采用的盐酸多西环素由河南省     

北京市养殖鱼类主要病原菌及其药物药敏性

正由于水产养殖环境恶化,各种水产病害频发,特别是细菌性疾病更为严重,已给养殖业造成重大经济损失。为此,本文针对北京地区开展养殖鱼类常见病原菌调查,并进行鱼类病原菌药物敏感性的监测,了解其耐药现状,构建药物敏感谱并不断更新,筛选出有效防治药物,指导养殖户科学合理使用抗菌药物。一、材料和方法(一)试验材料1.样品来源     

抗生素对中华鳖血液白细胞吞噬活性影响的初步研究

众多研究结果表明 ,进入机体内的致病菌的彻底清除 ,依赖于机体自身免疫系统与外界抗菌药物的共同作用[1,2 ] 。对于患病动物而言 ,正是由于机体防御机能和病原菌之间的作用平衡被打乱而使病原微生物得以在其体内大量繁衍。已有研究结果表明 ,选用适当的抗菌药物不仅能使进入机体内的病原菌的生长被抑制或杀灭 ,同时还能激发机体的某些免疫机能[2 ] 。然而 ,目前在水产养殖中选择使用防治细菌性疾病的药物时 ,几乎只考虑到了抗菌药物对致病菌的抑菌作用 ,而未考虑抗菌药物对机体免疫功能的影响问题。关于水产养殖中抗菌药物的免疫药理学研究…     

重组抗菌肽的制备及其对水产养殖中常见病原菌的抑菌效果

采用YEPD培养基诱导发酵生产重组抗菌肽。经 72h培养 ,由重组酵母表达并分泌到培养基中的抗菌肽活性可高达 5 0 0 0U/ml。用纸片扩散法和试管稀释法测定重组抗菌肽对水产养殖常见病原菌的抑菌效果。结果表明 ,抗菌肽对水产养殖常见病原菌嗜水气单胞菌 (Aeromonashydrophila)、梅氏弧菌 (Vibriometschnikovi)、迟钝爱德华氏菌 (Edwardsiellatarda)及温和气单胞菌 (A .sobria)有较好的抑菌效果 ,最小抑菌质量浓度为 4 μg/ml、杀菌质量浓度为 8μg/ml。对抗菌肽抑菌过程的超微结构观察表明 ,抗菌肽的抑菌方式是通过作用于细菌的细胞膜而导致菌体裂解死亡。本研究目的在于探讨基因工程抗菌肽在水产养殖中的应用。     

水产药物抗菌作用测定研究进展

目前对水产养殖动物细菌病进行控制的主要手段是采用抗菌药物治疗[1,2]。但由于对病原学、药理学等方面认识不全面,在养殖过程中存在高剂量多种药物混合使用等滥用、乱用药物现象,虽然对杀灭病原菌有一定的效果,但毒副作用明显,长期使用,易导致病原微生物产生抗药性。因此,在使     

水产动物源细菌耐药性与预防控制

细菌耐药性是指细菌对于抗菌药物作用的耐受性。细菌耐药性的形成,是细菌进化发展的结果,是细菌适应性的表现,但它却给养殖业的发展和人类的健康带来威胁。本文首先综述了水产动物源细菌耐药性研究现状,主要包括质粒介导的水产动物源细菌耐药性、细菌耐药基因、细菌耐药性遗传学机制等;其次,从病原菌耐药性会导致水产疾病流行爆发和水产细菌耐药性对人类公共卫生安全的影响两方面,分析了水产动物源细菌耐药性的危害;最后,从合理、规范用药,加快水产疫苗和新型抗菌药物替代品的研制与应用,加强水产动物致病菌耐药性监测等方面,提出了预防和控制水产动物源细菌耐药性的对策和措施。     

一元稳定性二氧化氯的优良特性及在水产养殖中的应用

较长时期以来,在我国的水产养殖业中,人们大多采用漂白粉、二氯异氰脲酸钠和三氯异氰脲酸等氯制剂作为消毒剂来杀灭病原菌,但由于长期使用,病原菌已产生耐药性,消毒效果也明显下降,特别是作用后可能产生三氯甲烷等具有致癌作用的物质,因此将氯制剂继续作为水产养殖消毒剂已存在明显的弱点。近年来,在国外,如美国、日本和欧洲的一些发达国家,逐渐用二氧化氯取代了上述氯制剂,在我国,一元稳定性二氧化氯作为一种新型渔药,已在水产养殖生产中逐渐开始应用,并取得了很好的效果。本报告结合二氧化氯的优良特性及在水产养殖的应用作一些简单的介绍…     

绿氧灵与光合细菌配合使用净化温室养鳖池水的效果

已经有大量的研究结果表明,绿氧灵(ClO2)是一种良好的水产用消毒剂。而光合细菌(简称PSB)是一类能进行光合作用而不产氧的特殊生理类群原核生物。有研究结果证明,PSB不仅能利用光能、固氮合成有机物,也能通过多种方式和途径转化不同类型的有机和无机物质,在水生态系统能量转换、物质循环和水体净化过程中起着十分重要的作用。PSB在水产养殖中的应用效果主要决定于PSB是否能在进入水体中后迅速大量繁殖,成为优势菌群。消除养殖池塘中原有的微生物对PSB的竞争,营造有利于PSB繁殖的生态环境是很有必要的。本研究采用绿氧灵消毒池水与使…     

氟苯尼考的体外抑菌作用及其对鲫抗嗜水气单胞菌感染的效果

研究了氟苯尼考对嗜水气单胞菌、副溶血弧菌、溶藻弧菌、鱼链球菌等水产动物主要病原菌的体外抑菌作用,并进一步观察了其对异育银鲫抗嗜水气单胞菌感染的效果。实验结果表明,氟苯尼考对嗜水气单胞菌、副溶血弧菌、溶藻弧菌、鱼链球菌具有良好的抗菌活性,最小抑菌浓度(MIC)分别为1mg/L、0.5mg/L、2mg/L、4mg/L。此外,投喂氟苯尼考的异育银鲫对抗嗜水气单胞菌感染具有良好的效果,以5,10,15mg/kg体重剂量将氟苯尼考拌饲投喂异育银鲫的平均死亡率与对照组相比分别降低了50%,70%,70%。     

Synthesis and characterization of Azadirachta indica constructed silver nanoparticles and their immunomodulatory activity in fish

Green synthesis of nanoparticles by using different biological agents has emerged as an alternative to overcome the toxic effect of chemically synthesized nanoparticles. Among various biological agents, plants are mostly preferred. This study describes an eco‐friendly and green synthesis of silver nanoparticles (G‐AgNPs) using Azadirachta indica (neem) as a reducing agent. UV–Vis spectral analysis proved the wavelength of sample to be 420 nm, approaching the surface resonance peak specific for G‐AgNPs. Dynamic light scattering (DLS) analysis showed the mean diameter of particles as 35.4 nm with zeta potential +34.6 mV. TEM results revealed the compact and spherical shape of the particles. Fourier transform infrared spectroscopies (FT‐IR) demonstrate the presence of possible functional groups involved in synthesis of the silver nanoparticles. The functional activity of immunological parameters, such as nitroblue tetrazolium assay, myeloperoxidase activity, phagocytic activity, anti‐protease and lysozyme activity, increased significantly (P < 0.05) in fish treated with G‐AgNPs. Relative percentage survival (74%) and enhanced disease resistance were observed in G‐AgNP‐treated Cirrhinus mrigala fingerlings challenged with Aeromonas hydrophila. In summary, present results demonstrate biosynthesized silver nanoparticles have immunomodulatory and antibacterial activity.     

Antibacterial activity of immobilized silver nanoparticles on TEPA‐Den‐SiO2 against shrimp pathogen,Vibrio sp. Persian1

In this study, we prepared silver nanoparticles immobilized onto silica sand beads as an antibacterial material against pathogenic luminous Vibrio sp. Persian1. Silica beads were modified with 3‐aminopropyltriethoxysilane (APTES), cyanuric chlorid and tetraethylene pentamine, and silver nanoparticles were generated in various concentrations (0.5, 1, and 2 mM g^?1 of silica beads) of AgNO₃ on the surface using chemical reduction. Ag/TEPA‐Den‐SiO₂ samples were characterized by TEM, FE‐SEM/EDS, FT‐IR and ICP OES and their antibacterial activity assayed by zone of inhibition and test tube tests against pathogenic Vibrio sp. The results of the zone inhibitory test revealed that all the Ag/TEPA‐Den‐SiO₂ samples had an antibacterial effect against luminous Vibrio sp. Persian1. In addition, the tube test results showed 100% killing of bacteria in 2 h contact period. Ag/TEPA‐Den‐SiO₂ samples maintained their antibacterial activity after 14‐day immersion in seawater by slow release of silver ions. These results suggest that Ag/TEPA‐Den‐SiO₂ substrates could be effective antibacterial materials for disinfection of seawater used to culture Penaeid shrimp larvae.     

纳豆菌脂肽对分离于对虾养殖环境中产T-2毒素镰孢菌抑制效应的研究

为了探明纳豆菌脂肽对对虾养殖环境中的产T-2毒素镰孢菌分离株的控制效应,实验采用扫描电镜观察了镰孢菌孢子超微结构、普通显微镜观察了菌丝形态、荧光显微镜观察了菌丝通透性.结果显示,脂肽浓度为1 mg/mL时,脂肽对镰孢菌孢子萌发的抑制率达78.8％,镰孢菌培养到第3天的生物量为不加脂肽对照的24.5％.扫描电镜观察结果表明,1 mg/mL的脂肽可以使镰孢菌的孢子呈念珠状;普通显微镜观察结果显示,1 mg/mL脂肽处理能使菌丝隔膜消失;荧光显微镜观察结果表明,脂肽能增加镰孢菌菌丝细胞膜的通透性.     

Sperm concentration in the mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> L.: a spectrophotometric measurement protocol

Quantifying spermatozoa concentration in milt samples is very important for aquaculture purposes, particularly when equal numbers of gametes are needed for experimental purposes, and different methods can be used. Haemocytometer and Coulter counting are the most precise methods to count spermatozoa, but they are very difficult to use when large numbers of samples are involved. A standard curve of spectrophotometric absorbance (A) against sperm concentration ([S]) was used herein instead, and an equation for estimating spermatozoa concentration for the mussel Mytilus edulis L. was obtained. The best wavelength to measure mussel spermatozoa was 320 nm, with a precision two or three times higher than at other wavelengths. The equation for spermatozoa concentration was A = 8.592 × 10⁻⁵ [S] + 0.0190 (r ² = 0.9979). Recommendations for choosing the best wavelength are discussed.     

Efficacy of bath and orally administered praziquantel and fenbendazole against Lepidotrema bidyana Murray,a monogenean parasite of silver perch,Bidyanus bidyanus (Mitchell)

We investigated the efficacy of praziquantel (PZQ) and fenbendazole (FBZ), each administered by bath and orally, against the monogenean Lepidotrema bidyana Murray, a gill parasite of the freshwater fish silver perch, Bidyanus bidyanus (Mitchell). PZQ and FBZ were each administered by bath at 10 mg L^?1 for 48 h and on surface‐coated feed pellets at 75 mg kg^?1 per body weight (BW) per day for 6 days. Bath treatments of PZQ and FBZ had an efficacy of 99% and 91%, respectively, against adult L. bidyana. Oral treatments of PZQ and FBZ had an efficacy of 79% and 95%, respectively, against adult L. bidyana. Fish rejected feed pellets surface‐coated with PZQ, suggesting that palatability of surface‐coated PZQ‐medicated feed is poor, which undermined efficacy. In all trials, some juvenile parasites were present on fish after treatment during efficacy assessment, indicating that efficacy may be lower against juvenile parasites or that recruitment occurred post‐treatment, demonstrating that repeat treatments are necessary to effectively control L. bidyana in aquaculture.     

Antibiofilm potential of a tropical marine Bacillus licheniformis isolate: role in disruption of aquaculture associated biofilms

Microbial biofilms are important in aquaculture industries as they resist antibiotic treatments. In this study, we have investigated the antibiofilm potential of a tropical marine culture Bacillus licheniformis D1 (containing an antimicrobial protein BLDZ1) against two aquaculture associated pathogens namely, Vibrio harveyi and Pseudomonas aeruginosa. Both the test cultures formed biofilms on polystyrene and glass surfaces. The cell free supernatant (CFS) of B. licheniformis inhibited V. harveyi and P. aeruginosa biofilms on polystyrene surfaces up to around 80% and 78% respectively. In addition, the CFS disrupted pre‐formed biofilms of test cultures by about 73%. Fluorescence and scanning electron microscope analysis confirmed the antibiofilm potential of the CFS. The cell free supernatant displayed antiadhesive activity that inhibited the initial attachment of the bacteria during the process of biofilm formation. In addition, the CFS exhibited antimicrobial activity and mediated cell death via cytoplasmic membrane disruption.     

Antibacterial activities of a new combination of essential oils against marine bacteria

The antibacterial activities of essential oils and herbal extracts have been demonstrated against a range of bacterial species. In this study, the antibacterial effects of a new combination of essential oils from the herbs Thymus vulgaris, Salvia officinalis, Eucalyptus globulus and Mentha piperita were assayed against common bacterial isolates (Staphylococcus aureus, Escherichia coli and Pseudomonas aeroginosa) and fifteen novel marine bacteria isolates. The sensitivity of different isolates to antibacterial activity of the essential oils was determined using well diffusion assays. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were quantified by micro dilution assays. The data demonstrate that the combination of essential oils had potent antibacterial effects and marine bacteria were more sensitive to growth inhibition (P < 0.05). MIC rates were 0.77–6.18 mg/ml, and MBC rates were 1.67–12.30 mg/ml. This indicates that the combined essential oils (CEO) can be a new source of antibacterial agents for use in marine aquaculture.     

Intestinal bacterial flora of Mediterranean gilthead sea bream (Sparus aurata Linnaeus) as a novel source of natural surface active compounds

Microbial communities play different functions in the digestive tract of fish and represent a source of bioactive compounds. This study was aimed to detect the presence of biosurfactant (BS)‐producing bacteria in the intestine of gilthead sea bream (Sparus aurata L.) to select strains candidate for biotechnological applications in aquaculture. A total of 100 bacterial strains were isolated from the guts of three groups of fish and analysed by different qualitative screening tests and the tensiometric analysis. BSs were extracted, characterized by thin‐layer chromatography (TLC) and their antibacterial activity against bacterial pathogens of interest in aquaculture was determined. A total of 17 out of 100 strains, affiliated to the genera Pseudomonas (11 isolates), Acinetobacter (1 isolate), Sphingomonas (4 isolates) and Aeromonas (1 isolate), displayed a stable emulsion production with the E₂₄ index from 0% to 44%, a surface tension reduction from 8.3 to 30 mN/m and 11 of them exhibited antibacterial activity against fish pathogens. The TLC analysis indicated that the intestinal BSs consisted of compounds ascribed to the class of glycolipids–rhamnolipids. This is the first study reporting on the isolation and selection of BS‐producing bacteria from fish gut, a natural novel source of surface active compounds with potential biotechnological applications in aquaculture.     

Identification and characterization of pathogenic bacteria isolated from dead masu salmon Oncorhynchus masou masou and antibacterial activity of probiotic Lactococcus lactis subsp. lactis strain K-C2 against isolated pathogens

We focused on developing an epidemic prevention method for circulating masu salmon aquaculture using the probiotic Lactococcus lactis strain K-C2. This study aimed to evaluate the antibacterial activities of strain K-C2 against pathogens isolated from dead Yamame and masu salmon. First, we identified pathogenic bacteria that were isolated from dead masu salmon based on phylogenetic analysis of the 16S rRNA gene sequence and biological and biochemical characterization. The antibacterial activity of strain K-C2 against seven pathogenic strains isolated from dead masu salmon in this study and two strains of Aeromonas salmonicida previously isolated from dead Yamame was tested using a double agar plate method. The results of a BLAST search using 16S rRNA partial sequence data (1200–1300 bp) revealed that six of the former strains and one of the latter strains showed high similarity to Vibrio anguillarum and Tenacibaculum maritimum, respectively. Strain K-C2 showed antibacterial activity against all pathogenic bacteria. In this study, pathogenic bacteria were newly isolated from dead seawater-acclimated masu salmon, and strain K-C2 was found to have antibacterial effects against these pathogens.

     

A Study on the antibacterial mechanism of thymol against Aeromonas hydrophila in vitro

As a zoonotic pathogen, Aeromonas hydrophila (A. hydrophila) not only has important economic significance in aquaculture but also plays an important role in global public health. With the abuse of antibiotics, the drug resistance of A. hydrophila has greatly increased, causing a poor therapeutic effect. It is particularly important to develop antibiotics alternatives against resistant bacteria. Thymol, a natural monoterpene phenolic compound, has been reported to have a variety of pharmacological effects. In this study, the effects of thymol on A. hydrophila were evaluated. The MIC and MBC of thymol to A. hydrophila were 128 μg/mL and 256 μg/mL, respectively. The results of the electron microscope showed that the bacterial cells contracted and deformed, the cell membrane was destroyed, and the cytoplasm was lost when treated with 2MIC thymol. Compared with the control group, the conductivity and the amount of DNA leakage of bacteria treated with 2MIC thymol increased by 2.45% and 66.4 μg/mL, respectively. In addition, LDH activity decreased by 25.93% after 2MIC thymol treatment. DAPI staining results showed that the intensity and quantity of fluorescence were significantly decreased in the drug treatment group. In summary, the antibacterial mechanism of thymol was to destroy the integrity of the cell membrane, make intracellular material exudate, and eventually lead to the death of bacteria. Thymol has the potential to be an antibiotics alternative against resistant bacteria.