快速检测双芽巴贝斯虫LAMP方法的建立

为提高双芽巴贝斯虫(Babesia bigemina)检出率,本研究采用环介导等温扩增技术(LAMP)建立一种快速、灵敏、特异的B.bigemina检测方法。根据GenBank上公布的Babesia bigemina细胞色素b(Cytochrome b,cyt b)基因序列,设计4条特异地识别B.bigemina的cyt b基因6个特殊区域的LAMP引物,优化反应体系和条件,在Bst DNA聚合酶的作用下,65 ℃反应60 min,加入SYBR Green Ⅰ后观察。结果表明,该LAMP检测方法特异性强,与牛巴贝斯虫(Babesia bovis)等DNA不发生交叉反应;敏感性高,对B.bigemina的cyt b基因最小检测值为0.085 fg/μL,是一般PCR方法的1000倍。该方法具有简单、快速、低成本的特点,可用于B.bigemina的基层现场快速检测。     

Rapid differentiation of Mycobacterium bovis and Mycobacterium tuberculosis based on a 12.7-kb fragment by a single tube multiplex-PCR

The aim of this work was the design and validation of a rapid and easy single tube multiplex-PCR (m-PCR) assay for the unequivocal differential detection of Mycobacterium bovis and Mycobacterium tuberculosis. Oligonucleotide primers were based on the uninterrupted 229-bp sequence in the M. bovis genome and a unique 12.7-kb insertion sequence from the M. tuberculosis genome, which is responsible for species-specific genomic polymorphism between these two closely related pathogens. The m-PCR assay was optimized and validated using 22 M. bovis and 36 M. tuberculosis clinical strains isolated from diverse host species and 9 other non-tuberculous mycobacterial (NTM) strains. The designed primers invariably amplified a unique 168-bp (M. bovis-specific) and 337-bp (M. tuberculosis-specific) amplicon from M. bovis and M. tuberculosis strains, respectively. The accuracy of the assay, in terms of specificity, was 100%, as none of the NTM strains tested revealed any amplification product. As little as 20 pg of genomic DNA could be detected, justifying the sensitivity of the method. The m-PCR assay is an extremely useful, simple, reliable and rapid method for routine differential identification of cultures of M. bovis and M. tuberculosis. This m-PCR may be a valuable diagnostic tool in areas of endemicity, where bovine and human tuberculosis coexist, and the distinction of M. bovis from M. tuberculosis is required for monitoring the spread of M. bovis to humans.     

猪圆环病毒2型LAMP检测方法的建立与评价

根据猪圆环病毒2型(Porcine circovirus type 2,PCV2)Rep和Cap基因保守区设计2对引物,1对外引物和1对内引物;利用设计的4条引物,在Bst大片段聚合酶的作用下,对PCV2 DNA进行恒温扩增;扩增条件为63℃恒温反应1h;建立了PCV2环媒恒温扩增技术(LAMP)检测方法。对检测方法特异性评价表明,检测方法只能检测PCV2 DNA,对猪圆环病毒1型(Porcine circovirus type 1,PCV1)、猪细小病毒(Porcine parvovirus,PPV)及猪伪狂犬病病毒(Porcine pseudorabies virus,PRV)检测无交叉反应。灵敏度评价表明,该检测方法可以检测到样品中10个拷贝的PCV2 DNA含量。     

犬瘟热病毒野毒株与疫苗株鉴别检测RT-LAMP方法的建立

为建立一种鉴别犬瘟热病毒(CDV)野毒株与疫苗株的反转录-环介导等温扩增方法(RT-LAMP),本研究通过比对野毒株与疫苗株H基因设计特异性引物,对反应体系中的Mg2+、Betaine、Bst DNA Polymerase、dNTP和反应温度等条件分别进行优化,建立用于鉴别检测CDV野毒株与疫苗株的RT-LAMP。建立的RT-LAMP方法检测CDV野毒株时,在65℃水浴锅中反应40 min即可完成。该方法具有高度特异性,对犬细小病毒、犬腺病毒、狂犬病毒、犬冠状病毒无交叉反应,敏感度可达40 copies/μL,是常规RT-PCR方法的100倍。     

Detection of Babesia bigemina infection in strains of Rhipicephalus (Boophilus) microplus collected from outbreaks in south Texas

The sudden death of several cattle infested experimentally with Rhipicephalus (Boophilus) microplus led to a clinical investigation into the reasons for the unexpected mortality. Microscopic evidence for Babesia bigemina infection was found in blood smears from the affected animals and a PCR assay was designed to detect the presence of B. bigemina and Babesia bovis in all R. microplus strains received and propagated at the laboratory. The assay utilizes a nested PCR approach with the first PCR amplifying a well-conserved segment from the Babesia 18S ribosomal RNA gene followed by a nested PCR with Babesia species-specific primers and annealing temperatures enabling amplification of the 18S ribosomal RNA gene fragment specific to either B. bigemina or B. bovis. DNA from groups of 50 larvae was extracted using a rapid DNA preparation protocol, which consisted of grinding the frozen tick larvae in PCR buffer and boiling the mixture for 5min. The assay sensitivity allowed for the detection of the equivalent of a single infected tick larva. R. microplus eggs were also analyzed, but yolk protein viscosity created inconsistent results with the crush and boil DNA isolation protocol, necessitating the use of a more extensive proteinase K digestion-based DNA purification method. We detected the presence of B. bigemina in all strains of R. microplus currently reared at the laboratory and 4 of 26 strains collected from infestation outbreaks in Texas by the U.S. Cattle Fever Tick Eradication Program.     

Validation of rt-PCR assays for molecular characterization of porcine teschoviruses and enteroviruses

Porcine enteroviruses (PEVs) and teschoviruses (PTVs) are described as causative agents of neurological disorders, fertility disorders and dermal lesions of swine. Difficulties in the serological detection of these viruses may lead to a significant underestimation of infections with clinical symptoms. With the recent availability of genome sequence data for all the serotypes, molecular diagnosis is a possibility. The present study describes a new approach to molecular 'serotyping' of PTVs and PEV-B viruses, involving the amplification and sequencing of a genomic fragment of the VP1 coding region. A molecular characterization of Italian entero-teschovirus isolates was performed using a set of previously published and newly designed polymerase chain reaction primers. A total of 33 porcine isolates and 10 reference strains were analysed. Porcine enterovirus-B samples were first diagnosed as positive for enterovirus by amplification of the 5'-non-translated region. Samples were then typed by amplification and sequencing of a portion of the VP1 coding region. Porcine enterovirus-A and PTVs were detected by a published assay in the 5'-NC region that allows them to be differentiated according to the size of amplification product, using the same set of primers. For serotype characterization of PTV, we evaluated four different regions: the N terminus of the capsid protein VP2, the region encoding for RNA-dependent RNA polymerase, and the capsid VP1 and VP4 regions. The newly designed primers in the VP1 region was proved to be broad in range and suitable for serotype assessment and therefore constitute a useful diagnostic tool for molecular diagnosis of porcine teschovirus/enterovirus strains and for the study of molecular epidemiology and evolution of these viruses.     

Rapid detection of group I avian adenoviruses by a loop-mediated isothermal amplification

A loop-mediated isothermal amplification (LAMP) assay was optimized for the rapid detection of Group I avian adenoviruses. A set of six primers was designed from the DNA sequences of hexon genes from Group I avian adenovirus. The assay was performed in a water bath for 60 min at 63 C, and the amplification result was visualized by adding a fluorescence dye reagent or by inspecting the white sediment. The results showed that the LAMP assay could detect all 12 serotypes of Group I avian adenovirus and nine Guangxi Group I avian adenovirus isolates. This avian adenovirus Group I-specific LAMP assay could detect 238 copies of avian adenovirus. No cross-reactions were detected using the LAMP assay with avian adenoviruses type II and III or with other avian viruses. The ability of LAMP to detect Group I avian adenovirus isolates was further evaluated with 184 cloacal swab samples from poultry. In total, 72 out of 184 cloacal swab samples from poultry were identified as positive by LAMP, whereas 45 out of 184 were identified as positive by conventional PCR test. The Group I avian adenovirus specific LAMP results were further confirmed by real-time PCR. This specific LAMP method holds promise as a rapid and specific diagnostic assay for detection of samples from birds suspected of adenovirus infection.     

Genomic heterogeneity of small ruminant lentiviruses detected by PCR.

In order to detect a large spectrum of small ruminant lentiviruses, primers for PCR were chosen in conserved parts of the LTR and GAG genes of Icelandic Visna virus 1514 and of the POL gene of caprine arthritis-encephalitis virus. This set of primers was tested in six different caprine arthritis-encephalitis virus (CAEV)- and Maedi-Visna virus isolates of Dutch, American and Swiss origin. The LTR primers allowed the detection of the corresponding fragments of all isolates. The GAG primers allowed amplification of the corresponding fragments of all but the Swiss Maedi-Visna virus strain OLV. Using the POL primers, one Maedi-Visna- and two caprine arthritis-encephalitis virus strains were detected after one round of amplification. Sequencing of the GAG and POL amplification products and comparison to Icelandic Visna virus and CAEV strain CO revealed total heterogeneity of 38% for the GAG- and 28% for the POL fragment. The virus strains studied fall into two groups which are more closely related to one another than to Icelandic Visna virus.     

猪脑心肌炎病毒RT—LAMP检测方法的建立

针对猪脑心炎病毒（Encephalomyocarditis virus,EMCV）3D基因保守序列的6个特异性部位设计了2对引物,利用BstDNA聚合酶,63℃恒温保持50min即可完成反转录与扩增反应,产物中加入SYBR GreenI染料,在紫外光下可直接观察判定扩增结果,试验成功建立了猪EMCV的RT-LAMP检测方法。结果表明：该方法灵敏度比RT-PCR高100倍,具有良好的重复性和稳定性,而且对其他病毒均无扩增结果,可作为猪EMCV的快速诊断方法。     

Establishment and Application of Loop-mediated Isothermal Amplification for Rapid Detection of Porcine Epidemic Diarrhea Virus

This study was aimed to establish a loop-mediated isothermal amplification (LAMP) assay for detection of porcine epidemic diarrhea virus (PEDV), and provide a simple, sensitive, accurate and reliable tool for diagnosis of PEDV.The conservative PEDV N gene (GenBank accession number: KT799997) of PEDV was selected as a target to design six specific primers.The reaction system and temperature of LAMP were optimized, and the LAMP method for specific amplification of PEDV was established. Results showed that the PEDV LAMP detection method was established successfully, and it could detect PEDV specifically at 60℃ for 60 min,and the detection limit was 91 copies/μL, which was one hundred-fold higher than conventional RT-PCR method.75 clinical samples were detected by LAMP and PCR, respectively, the coincidence of LAMP and PCR was about 97.3%. All the data suggested that the LAMP assay had strong specificity, high sensitivity, simple operation, low equipment requirement, and was suitable for rapid detection of PEDV clinical samples.     

猪流行性腹泻病毒环介导等温扩增检测方法的建立及应用

试验旨在建立一种快速检测猪流行性腹泻病毒（PEDV）的环介导等温扩增方法（LAMP）,为诊断PEDV提供简便、敏感、准确可靠的工具。参考GenBank中PEDV基因序列（登录号：KT799997）,针对PEDVN基因设计了6条引物,对所建立的LAMP反应体系、反应温度进行优化,建立可特异性扩增PEDV的LAMP方法。结果显示,本试验成功建立了PEDV LAMP检测方法,在60℃恒温下反应60 min,能特异性地检测PEDV,检测限量为91拷贝/μL,比常规PCR方法的敏感性高100倍。对比75份临床样本的LAMP和常规RT-PCR法检测结果,显示两种方法符合率为97.3%。综上所述,本试验建立的LAMP方法具有特异性强、敏感性高,操作简单,设备要求低的特点,适用于PEDV临床样本的快速检测。     

羊丝状支原体簇环介导等温扩增检测方法的建立

本试验利用环介导等温扩增技术(LAMP)建立了羊丝状支原体簇的快速检测方法,该方法以羊丝状支原体簇成员的保守性基因16S rRNA为靶序列,设计了4条特异性引物,在65 ℃等温条件下,60 min一步完成反应。在反应管中预先添加羟基萘酚蓝(HNB),阳性呈蓝色,阴性呈紫色。丝状支原体簇成员——丝状支原体山羊亚种(Mmc)、丝状支原体丝状亚种LC型(Mmm LC)、山羊支原体山羊肺炎亚种(Mccp)的LAMP检测为阳性;对其他病原菌没有交叉反应。以Mmc的核酸为模板进行灵敏度检测,LAMP的最低检出限为10 pg/μL。结果表明,本试验建立了一种特异、敏感、快速、简便的羊丝状支原体簇的LAMP方法。     

Validation of RT‐PCR Assays for Molecular Characterization of Porcine Teschoviruses and Enteroviruses

Porcine enteroviruses (PEVs) and teschoviruses (PTVs) are described as causative agents of neurological disorders, fertility disorders and dermal lesions of swine. Difficulties in the serological detection of these viruses may lead to a significant underestimation of infections with clinical symptoms. With the recent availability of genome sequence data for all the serotypes, molecular diagnosis is a possibility. The present study describes a new approach to molecular ‘serotyping’ of PTVs and PEV‐B viruses, involving the amplification and sequencing of a genomic fragment of the VP1 coding region. A molecular characterization of Italian entero‐teschovirus isolates was performed using a set of previously published and newly designed polymerase chain reaction primers. A total of 33 porcine isolates and 10 reference strains were analysed. Porcine enterovirus‐B samples were first diagnosed as positive for enterovirus by amplification of the 5′‐non‐translated region. Samples were then typed by amplification and sequencing of a portion of the VP1 coding region. Porcine enterovirus‐A and PTVs were detected by a published assay in the 5′‐NC region that allows them to be differentiated according to the size of amplification product, using the same set of primers. For serotype characterization of PTV, we evaluated four different regions: the N terminus of the capsid protein VP2, the region encoding for RNA‐dependent RNA polymerase, and the capsid VP1 and VP4 regions. The newly designed primers in the VP1 region was proved to be broad in range and suitable for serotype assessment and therefore constitute a useful diagnostic tool for molecular diagnosis of porcine teschovirus/enterovirus strains and for the study of molecular epidemiology and evolution of these viruses.     

RT-PCR鉴别小反刍兽疫病毒疫苗株与强毒株方法的建立

根据GenBank中公布的小反刍兽疫病毒的H基因或全基因序列,利用软件Primer Premier5.0设计引物,扩增片段长度为477bp,建立区分小反刍兽疫疫苗毒与基因4系野毒的RT-PCR检测方法,并用于临床检测。结果表明,建立的RT-PCR鉴别诊断方法能特异性区分疫苗株Nigeria75/1与基因4系PPRV,与基因3系、牛瘟病毒、犬瘟热病毒等同属病毒无交叉反应;最低可以检测到浓度为7.7×10-5ng/μL的RNA模板;该方法操作简单,耗时短,可以初步用于临床鉴别诊断。     

应用环介导等温扩增技术快速检测单核细胞增生李斯特菌的研究

目的建立环介导等温扩增技术快速检测单核细胞增生李斯特菌。方法根据单核细胞增生李斯特菌(LM)hlyA基因序列中的保守区域,采用在线引物设计软件Primer Explorer4.0进行设计,获得一套特异性的环介导等温扩增(LAMP)引物,对单核细胞增生李斯特菌hlyA基因进行LAMP扩增,并与常规PCR方法进行比较。结果建立的LAMP方法能成功扩增出梯形条带,LAMP检测单核细胞增生李斯特菌纯培养物和人工染菌的灵敏度为5.44×102cfu/mL,而对照PCR检测的灵敏度为5.44×104cfu/mL。对10株细菌进行LAMP扩增,仅单核细胞增生李斯特菌得到阳性结果。从DNA提取到报告结果,耗时仅1h。结论 LAMP检测单核细胞增生李斯特菌灵敏度高,特异性强,耗时短,方法简便,有望发展成为快速检测食品中单核细胞增生李斯特菌的有效手段。     

Development of a loop-mediated isothermal amplification assay for rapid, sensitive and specific detection of a Campylobacter jejuni clone

Loop-mediated isothermal amplification (LAMP) assay is a simple, rapid and specific detection method and has been used for detection and identification of different Campylobacter species. In this study, we develop a LAMP assay specific for detection of a particular clone (clone SA) of Campylobacter jejuni, associated with the vast majority of recent sheep abortions in the U.S. Using a set of specific primers for C. jejuni IA3902 (a clone SA isolate) and genomic DNA or boiled cell extract as template, the target DNA was amplified at 63 °C for 50 min in a water bath. A positive reaction was identified visually as white precipitate or fluorescence under UV, and confirmed by gel electrophoresis. Detection limit of the assay was comparable to that of conventional PCR. The LAMP was shown to be specific for detection of clone SA when tested on a number of C. jejuni strains of different genetic backgrounds. Applicability of the LAMP assay for specific detection of clone SA was demonstrated in animal tissues experimentally infected with IA3902 or genetically diverse C. jejuni strains. Since clone SA is the predominant cause of sheep abortions in the U.S. and is a zoonotic pathogen, the LAMP assay may be a valuable detection tool in future epidemiological studies.     

Development of Loop-mediated Isothermal Amplification Assay for Detection of Torque teno sus Virus Type 2

In order to develop a loop-mediated isothermal amplification (LAMP) assay for rapid and specific detection of Torque teno sus virus type 2 (TTSuV2), two pairs of primers were designed according to the untranslated regions and the part of open reading frame 1 of TTSuV2.The LAMP system was optimized by adjusting the concentrations of some components and reaction conditions.The optimized amplification conditions of LAMP assay was at 64 ℃ for 90 min.The results showed the LAMP assay was specific for TTSuV2 detection, which could achieve a detection limit of 100 copies/μL viral nucleic acid, and no cross-reaction with TTSuV1, PCV2, CSFV, PRRSV and PBoV.In conclusion, this assay was a rapid, specific and sensitive detection technique which could provide a assistance for the rapid detection of TTSuV2.     

猪细环病毒2型环介导等温扩增检测方法的建立

为了能快速、特异的检测猪细环病毒2型(TTSuV2),本研究针对TTSuV2全基因序列的非编码区域和第1个开放性阅读框前端设计了2对引物,建立了TTSuV2的环介导等温扩增(LAMP)检测方法并对反应成分和条件进行了梯度摸索。试验结果显示,该LAMP检测方法最佳反应条件为64 ℃恒温90 min,可特异性检测TTSuV2,与猪细环病毒1型、猪圆环病毒2型、猪瘟病毒、猪繁殖与呼吸综合征病毒和猪博卡病毒无交叉反应,病毒最低检出限为100拷贝/μL。结果表明,建立的LAMP方法具有快速、特异且灵敏的特点,可在TTSuV2快速检测方面提供一定的技术支持。