Development of a multiplex PCR assay to detect Edwardsiella tarda,Streptococcus parauberis,and Streptococcus iniae in olive flounder (Paralichthys olivaceus)

A multiplex PCR protocol was established to simultaneously detect major bacterial pathogens in olive flounder (Paralichthys olivaceus) including Edwardsiella (E.) tarda, Streptococcus (S.) parauberis, and S. iniae. The PCR assay was able to detect 0.01 ng of E. tarda, 0.1 ng of S. parauberis, and 1 ng of S. iniae genomic DNA. Furthermore, this technique was found to have high specificity when tested with related bacterial species. This method represents a cheaper, faster, and reliable alternative for identifying major bacterial pathogens in olive flounder, the most important farmed fish in Korea.     

Development of a diagnostic PCR assay based on novel DNA sequences for the detection of Mycoplasma suis (Eperythrozoon suis) in porcine blood

An efficient method of control of porcine eperythrozoonosis (PE) caused by Mycoplasma suis is eradication of infection by detection and removal of infected carrier animals. At present, only a few tests are available for the diagnosis of these latent M. suis infections in pigs. The objective of this study was to develop a PCR assay based on novel DNA sequences for the identification of M. suis-infected pigs. A 1.8 kb EcoRI DNA fragment of the M. suis genome was isolated from the blood of pigs experimentally infected with M. suis. Specificity of the DNA fragment was confirmed by DNA sequence analysis and PCR using primers directed against sequences contained in the 1.8 kb fragment. PCR products of 782 bp in size were amplified only from M. suis particles prepared from the blood of experimentally infected pigs but not from any controls, comprising blood from gnotobiotic piglets and a panel of bacteria including other porcine mycoplasmas. PCR results were confirmed by dot blot hybridisation. The applicability of the PCR assay to diagnose M. suis infections in pigs was evaluated by investigating blood samples from 10 symptomatic pigs with clinical signs typical of porcine eperythrozoonosis and blood samples from 10 healthy pigs. The M. suis-specific PCR product was amplified from all samples taken at episodes of acute disease as well as from samples taken during the latent stage of infection, thus demonstrating the suitability of the PCR assay for detecting latent infected carrier animals.     

Development of a sensitive and quantitative diagnostic assay for fish nervous necrosis virus based on two-target real-time PCR

The aim of the present work was to develop two new independent SYBR Green I-based real-time PCR assays for both detection and quantification of betanodavirus, an RNA virus that infects several species of marine teleost fish causing massive mortalities in larvae and juveniles. The assays utilized two pairs of primers targeting highly conserved regions of both the RNA molecules forming the betanodavirus genome: RNA1 encoding the RNA-dependent RNA polymerase (RdRP) and RNA2 encoding the coat protein (CP). The specificity of amplifications was monitored by the melting analysis and agarose gel electrophoresis of the amplified products. The applicability of these assays was confirmed with 21 betanodavirus strains, covering all the four main clades. In addition, a BLAST (NCBI) search with the primer sequences showed no genomic cross-reactivity with other viruses. The new assays were able to quantify concentrations of betanodavirus genes ranging from 10¹ to 10⁸ copies per reaction. The intra-assay coefficients of variation (CV) of threshold cycle (C_t) values of the assays were 1.5% and 1.4% for CP and RdRP RNAs, respectively. The inter-assay CVs of C_t values were 2.3% and 2.4% for CP and RdRP RNAs, respectively. Moreover, regression analysis showed a significant correlation (R² > 0.97) between genome number, as determined by real-time PCR assays and the corresponding virus titer expressed as TCID₅₀/ml of two different betanodavirus strains propagated in cell culture. The two assays were compared with a previously established one-step RT-PCR assay and with the classical virus isolation test and found to be more sensitive. In conclusion, the developed real-time RT-PCR assays are a reliable, specific and sensitive tool for the quantitative diagnosis of betanodavirus.     

牛附红细胞体病PCR诊断方法的建立

根据已报道的牛附红细胞体16S rRNA的序列设计1对特异性引物,进行PCR.将PCR产物克隆并测序,结果显示所得基因片段为667 bp,与GenBank上Mycoplasma weyonii序列同源性达到98.83%.试验建立的PCR诊断方法特异性强,与健康牛血液、牛无乳链球菌、金黄葡萄球菌、多杀性巴氏杆菌、胸膜肺炎放线杆菌、大肠杆菌的DNA无交叉反应,能检测的牛附红细胞体最低DNA质量浓度是13.6 ng/L.应用该方法对130个奶牛血样进行牛附红细胞体病检测,结果表明总阳性感染率为24.62%.该方法具有快速、准确、敏感等特点,为牛附红细胞体病的诊断及分子流行病学的调查提供新的手段.     

Development and clinical evaluation of a PCR assay targeting the metalloprotease gene (mprA) of B. pseudomallei

A PCR assay targeting the metalloprotease gene (mprA) of Burkholderia pseudomallei was developed for the specific detection of this organism in pure cultures and clinical samples. All other closely related organisms including B. mallei the causative agent of glanders, and B. thailandensis tested negative. Burkholderia pseudomallei DNA was successfully amplified from paraffin-embedded lung tissue of a camel with a generalized B. pseudomallei infection. The developed PCR assay can be used as a simple tool for the specific and sensitive detection of B. pseudomallei.     

Development of a differential multiplex PCR assay for equine herpesvirus 1 and 4 as a diagnostic tool

In this study, a multiplex polymerase chain reaction (PCR) procedure was developed for differentiation of strains and field isolates of equine herpesvirus type 1 (EHV-1) and type 4 (EHV-4). Specific oli-gonucleotide primers were combined to amplify the thymidine kinase (TK) gene region of EHV-1 and EHV-4, which would yield fragments of different lengths for each virus in the same amplification reaction. The specificity of the largest PCR amplicon for EHV-4 was confirmed by restriction digestion with HindIII. The multiplex PCR proved to be a fast and sensitive method for typing EHV-1 and EHV-4 isolates and for detection and differentiation of both viruses in field samples in which infectious virus is no longer available. The sensitivity was improved by combining cycling optimization and visualization of PCR products in ethidium bromide and silver-stained acrylamide gels.     

一种基于CP204L基因的非洲猪瘟病毒Taq Man-MGB实时荧光PCR检测方法的建立

基于非洲猪瘟病毒(ASFV)CP204L基因序列设计1对特异性引物和TaqMan-MGB探针,通过优化反应条件建立了一种检测ASFV的TaqMan-MGB实时荧光PCR方法。结果显示,该方法仅对ASFVDNA呈现特异性扩增,不与猪的其他常见病毒发生交叉反应,具有良好的特异性。该方法对标准对照质粒(PCR2.1-CP204L)的线性检测范围为4.2×10~1~4.2×10~9copies/μL,标准曲线方程为Y=-3.452 3X+39.014,相关系数(R~2)为0.998 8,检测下线为4.2个拷贝。对5个不同浓度(4.2×10~3~4.2×10~7copies/μL)的质粒标准品进行4次双份样品的重复检测,Ct值变异系数均小于1.5%,表明该方法具有良好的重现性。用该方法对总计164份的进口猪临床样品和生猪肌肉样品进行ASFV检测,结果均为阴性。该方法的建立为活猪临床样品和生猪肌肉样品中ASFV检测提供了一种快速、敏感和特异的技术手段。     

基于猪伪狂犬病毒gE基因的PCR法快速诊断猪伪狂犬病的研究

为了建立一种快速检测猪伪狂犬病毒(PRV)的方法,试验采用PCR法,并以NCBI公布的PRV Min-A株(登录号为AY170318.1)的gE基因序列为参考序列设计1对特异性引物,进行PRV基因的扩增,并对该检测方法的特异性、敏感性、重复性进行验证。结果表明:该PCR检测方法扩增的目的基因长348 bp;应用此方法对猪繁殖与呼吸综合征病毒(PRRSV)、猪圆环病毒Ⅱ型(PCV2)、猪瘟病毒(CSFV)、猪细小病毒(PPV)进行PCR扩增均未有条带出现;该方法能够检测到的最低DNA模板量为10 pg;重复性良好;应用此法对43份临床样品进行检测,检出率为65.12%(28/43)。说明该PCR检测方法可用于PRV的分离鉴定、临床病料检测和分子流行病学调查等。     

Development of a diagnostic gene expression assay for tuberculosis and its use under field conditions in African buffaloes (Syncerus caffer)

The development of diagnostic tests for tuberculosis (TB) in exotic species is constrained by host biology and the limited availability of suitable assay reagents. As such, we evaluated a gene expression assay (GEA) which is easily modified for novel species and allows for initial sample processing under field conditions. African buffaloes (Syncerus caffer) were categorized using the single comparative intradermal tuberculin test, and blood from test-positive and test-negative animals was incubated for 20h in "Nil" tubes (containing saline) and "TB Antigen" tubes (containing Mycobacterium tuberculosis complex (MTC)-specific antigens) of a commercial human TB test, the QuantiFERON(?)-TB Gold (In-Tube) (QFT) assay. Blood samples were then stabilized in RNAlater(?) and transported to the laboratory for RNA extraction. A Custom TaqMan GEA was used to calculate the relative abundance of interferon-gamma (IFN-γ) mRNA in the TB Antigen tube compared to that in the Nil tube as a marker of immune activation in response to MTC antigen recognition. The GEA results from the two buffalo groups were compared and a cutoff value of 2.85 was calculated to differentiate between animals from these groups with a sensitivity of 80% (95% C.I.: 56-94%) and a specificity of 95% (95% C.I.: 75-100%). Further optimization of this assay could provide a highly useful tool for the diagnosis of MTC infection in exotic species.     

猪传染性胸膜肺炎PCR诊断方法的建立

根据已发表的猪胸膜肺炎放线杆菌APXIV毒素的基因序列，自行设计和合成了二对可扩增448bp和365bp目的片段的引物，成功的建立了检测APP的套式PCR方法。通过对猪肺疫巴氏杆菌、猪链球菌、大肠杆菌、猪嗜血杆菌、猪肺炎支原体和猪丹毒杆菌的DNA进行了PCR检测，结果均为阴性；对猪胸膜肺炎放线杆菌的1、2、5、6、7、9国际标准血清型均扩增出448bp和365bp的特异性条带；检测的敏感度一步PCR可达到5OO个细菌，最低检出DNA浓度可达到0．585ng／mL；套式PCR可达到50个细菌，最低检出DNA浓度可达到58．5pg／mL。另外，对5株从病猪体内分离的猪胸膜肺炎放线杆菌进行了检测，5株均成阳性反应；对10只屠宰猪的肺脏分离物进行了检测，结果1份为阳性。结果表明此法特异性和敏感性均很高，可做为猪传染性胸膜肺炎的快速诊断和流行病学调查的手段。     

羊痘病毒多重PCR检测方法的建立

根据羊痘病毒（CaPV）末端反向重复序列中的一段序列和P32基因序列,设计合成了2对引物,通过确定最佳的PCR反应条件,建立了检测羊痘病毒核酸的多重PCR方法。结果显示,用这2对引物均能扩增出羊痘病毒相应的特异性片段,而用此PCR方法检测口蹄疫病毒和羊口疮病毒,结果均为阴性。与中和试验比较,建立的PCR方法具有更好的敏感性。表明,该PCR方法可对组织病料中的CaPV进行快速检测。     

鹅圆环病毒实时荧光定量PCR检测方法的建立

为建立鹅圆环病毒(GoCV)快速检测方法,本研究根据GenBank中登录的GoCV全长基因组序列,在其保守基因区设计并合成1对引物,采用荧光嵌合法(SYBR GreenⅠ)建立检测GoCV的实时荧光定量PCR(real-time PCR)方法。以本实验室构建的含有GoCV永康株(GoCV-yk01)全长基因组的重组质粒为标准模板,经退火温度、循环次数等反应条件的优化,绘制GoCV real-time PCR的标准曲线,并进行融解曲线分析。试验结果表明:建立的GoCV real-time PCR方法特异性强,检测范围广(Ct值范围12～32),最低检出病毒拷贝数为1.46×102。该方法能够对组织中病毒进行定量检测,为快速检测GoCV提供了有效的技术手段。     

牛支原体套式PCR检测方法的建立

为建立牛支原体检测方法,本研究采用牛支原体的oppD/F基因的两对特异性引物,建立了牛支原体的套式PCR检测方法.该套式PCR可以从100 ccu/mL(color change unit颜色变化单位)的牛支原体培养物中检出目的片段;同时还可以从病牛肺脏、病牛鼻拭子中扩增出目的片段,而且结果与病原分离结果一致.特异性试验结果表明,该方法与其它支原体无交叉反应,是一种特异性强、敏感性高的牛支原体检测方法.     

猪链球菌2型LUX荧光PCR检测方法的建立

猪链球菌2型是一种严重的人兽共患病病原,为满足猪链球菌2型快速检测的需要,本研究根据猪链球菌2型Cps2J保守区设计LUX引物,首次利用LUX PCR方法对猪链球菌2型进行检测,并进行了敏感性和特异性试验及模拟样品检测试验。结果显示,本研究建立的猪链球菌LUX 荧光PCR检测方法具有较好的敏感性和特异性,检测质粒样品的敏感性为10拷贝,检测模拟样品敏感性为10²拷贝,与无乳链球菌、巴氏杆菌、粪链球菌、马链球菌兽疫亚种、沙门氏菌等无交叉反应。该方法的建立为猪链球菌2型的快速检测提供了新的途径。     

鸡传染性支气管炎病毒Real-time PCR方法的建立及其对感染鸡体内病毒的检测

本研究针对传染性支气管炎病毒（IBV）tl／CH／LDT3／03毒株的N基因（GenBank登录号为AY702975）设计并合成了一对引物,构建重组质粒作为阳性标准品,建立了检测IBV核酸的SYBRGreenⅠ荧光定量PCR方法。该方法可检测到初始模板中6．45×10copies／μL的病毒核酸。与常规PCR相比,敏感性高100倍。该检测方法特异性强,与其它禽源病毒如新城疫病毒（NDV）、传染性喉气管炎病毒（ILTV）、传染性法氏囊病毒（IBDV）、禽流感病毒（AIV）、马立克氏病毒（MDV）均不发生交叉反应;重复性试验的变异系数小于2．6％。结果表明,本试验建立的荧光定量PCR检测方法灵敏度高、特异性强、重复性好,可用于传染性支气管炎的临床诊断。同时应用本方法对人工感染IBV的SPF鸡的主要脏器盲肠扁桃体、肾脏、肺和气管进行了病毒RNA定量检测,结果表明,肾脏的病毒含量最高,盲肠扁桃体中病毒持续的时间最长,从而揭示了IBV在SPF鸡体内复制的动态变化,证实了感染鸡的临床表现与病毒滴度的时间相关性。     

猪Hokovirus PCR检测方法的建立及其应用

猪Hokovirus(PHoV)是近年来在香港发现的一种猪细小病毒。为及时评估该病毒在我国的感染及流行情况,本研究根据GenBank中登录的PHoV核苷酸序列设计并合成一对特异性引物,建立了PHoV的PCR检测方法。研究结果表明,所建立的PCR检测方法特异性强,对其它的猪主要病毒无交叉反应;敏感性较高,最低可以检测2.4×104拷贝/μL;而且重复性较好。采用该方法对2009年～2010年我国华东地区猪场的318份临床样品进行检测,结果显示38份样品为PHoV阳性,表明我国猪群中存在PHoV感染。本研究建立的PCR方法可以作为在临床上检测PHoV的一种有效手段。     

羊痘病毒实时荧光定量TaqManPCR检测方法的建立

参照羊痘病毒（CaPV）P32的基因序列，设计合成了2套引物和1条探针，建立了实时荧光定量PCR技术，对细胞培养物、皮肤丘疹、痂皮等组织病料中的GPV进行了特异性检测和敏感性试验。结果显示，用300nmol／L引物浓度和200nmol／L探针浓度，获得的CT值较小，而△Rn最大；可检测到相当于0．1TCID50的病毒DNA；制作的标准曲线中各浓度范围内有极好的线性关系且线性范围宽，相关系数为0．9995以上；组内和组间试验重复性的变异系数分别为2．3％和3．4％；与常规的PCR相比较，该方法具有快速、特异、敏感、可定量，可同时检测大量样品等优点。表明，荧光TaqMan PCR是一种检测CaPV的良好方法，可对组织病料中低含量的CaPV或持续带毒宿主进行准确检测。     

绵羊肺炎支原体和溶血性曼氏杆菌双重PCR检测方法的建立及应用

为建立同时检测绵羊肺炎支原体(MO)和溶血性曼氏杆菌(Mh)的方法,本研究根据MO的hsp70基因和Mh的gcp基因分别设计引物,建立了同时检测这两种病原的双重PCR检测方法.实验结果显示该方法能够特异性的扩增MO (135 bp)和Mh (227 bp) DNA片段,其最低检出量分别为2.06×103拷贝/μL和6.37 c fu/mL,与单一PCR相同.该方法对常见的致病菌无交叉反应.对临床样本的检测结果显示MO和Mh的检出率分别为56.25％和52.50％,与单独PCR符合率为100％.研究结果表明,本研究所建立的双重PCR检测方法具有特异性强、敏感性高等特点,为临床上MO和Mh混合感染的快速检测、鉴定以及流行病学调查提供了方便、快捷、准确的方法.     

Effectiveness of aquaflor (50% florfenicol) to control mortality associated with Streptococcus iniae in freshwater-reared subadult sunshine bass

We conducted a field trial to evaluate the effectiveness of Aquaflor (50% florfenicol) for controlling mortality associated with Streptococcus iniae in freshwater-reared subadult sunshine bass (female white bass Morone chrysops X male striped bass M. saxatilis). Bacterial samples collected from moribund fish representing a reference population were presumptively identified microbiologically and were later confirmed to be S. iniae by biochemical characterization and polymerase chain reaction. The trial comprised a 1-d acclimation period, 10-d treatment period, and 14-d posttreatment period. During the treatment period, Aquaflor-medicated feed was administered to treated tanks (N = 3) at a target dose of 10 mg of florfenicol x kg of fish(-1) x d(-1), and nonmedicated feed was administered to control tanks (N = 3). At the end of the posttreatment period, mean (+/- SD) cumulative mortality in treated tanks (9 +/- 11%) was significantly (P = 0.040) less than that in control tanks (52 +/- 13%). Analysis of medicated feed samples revealed that treated tanks had received an actual dose of 8.3 mg florfenicol x kg fish(-1) x d(-1) (83% of target). No florfenicol was detected in control feed samples. Although the actual florfenicol dose administered to treated tanks was less than the target dose, the trial was accepted by the U.S. Food and Drug Administration Center for Veterinary Medicine as demonstrating the efficacy of Aquaflor to control mortality associated with S. iniae in cultured sunshine bass populations.