多重PCR检测原料乳中沙门氏菌、无乳链球菌和金黄色葡萄球菌的研究

目的:建立快速检测沙门氏菌、无乳链球菌和金黄色葡萄球菌的多重PCR方法。方法:根据沙门氏菌(Salmonella)组氨酸转运操纵子基因、无乳链球菌(Streptococcus agalactiae)的STRA-Agl-23-1D基因和金黄色葡萄球菌(Staphylococcus aureus)的耐热核酸酶nuc基因分别设计引物,进行PCR扩增及反应条件的优化,建立这3种菌的多重PCR检测方法。结果:通过建立多重PCR方法,3对引物同时特异性地扩增出495 bp、360 bp和279 bp目的片段;3种菌的检测限:沙门氏菌1.9×102 cfu/mL、无乳链球菌2.0×102 cfu/mL、金黄色葡萄球菌2.9×102 cfu/mL;3种菌DNA含量的(最低)检出限分别为3.86、25.5、3.47pg。结论:本文建立的多重PCR检测方法,简单、快速、灵敏度高,具有很好的应用前景。     

FTA滤膜与多重PCR结合检测肉中3种食源性致病菌

采用FTA滤膜从肉中直接提取模板DNA,根据金黄色葡萄球菌的nuc基因、沙门氏菌的IpaB基因、福氏志贺氏菌的ipaH基因设计3对特异性引物,进行多重PCR检测.结果表明,3对引物能特异性扩增出210、280、393bp大小的目的条带;在不增菌的情况下,多重PCR同时检测肉中3种致病菌的灵敏度均为102 cfu/g,检测时间6 h.该检测方法准确、快速、高效,为同时检测肉中金黄色葡萄球菌、沙门氏菌、福氏志贺氏菌奠定了基础.     

多重PCR快速检测三种食品病原菌

建立一种快速、经济、实用的可以同步检测食品中金黄色葡萄球菌、沙门氏菌、小肠结肠炎耶尔森氏菌的多重聚合酶链式反应(polymerase chain reaction,PCR)的方法。根据金黄色葡萄球菌的nuc基因,沙门氏菌的invA基因,小肠结肠炎耶尔森氏菌的ail基因,分别设计了三对引物,对单个基因PCR和单管多重PCR扩增进行特异性、灵敏性实验以及优化反应体系。三对引物能特异性扩增出236、475、127bp的目的条带。建立的多重PCR同时对3种食源性致病菌进行检测具有较高的灵敏度,灵敏度金黄色葡萄球菌为102CFU/mL、沙门氏菌为102CFU/mL、小肠结肠炎耶尔森氏菌为102CFU/mL。初步建立能同步、简便、快速、灵敏地检测食品中金黄色葡萄球菌、沙门氏菌和小肠结肠炎耶尔森氏菌的三重PCR方法。     

肉中4种致病菌的PCR快速检测方法的建立

目的:建立一种能同时检测肉中金黄色葡萄球菌、志贺氏菌、沙门氏菌和单核增生李斯特菌的多重PCR检测方法。方法:根据金黄色葡萄球菌的耐热核酸酶基因(nuc)、沙门氏菌的侵袭蛋白基因(invA)、志贺氏菌的侵袭性质粒抗原基因(ipaH)和单核细胞增生性李斯特菌的内化素基因(inlA)设计引物,通过优化好的反应体系进行多重聚合酶链反应(PCR)扩增目的基因。结果:特异性实验结果表明4种菌均能在相应位置扩增出特异性条带。对污染4种菌的猪肉进行检测,确定出金黄色葡萄球菌和沙门氏菌的检出限是102CFU/mL,志贺氏菌和单核增生李斯特菌的检出限是101CFU/mL。结论:本实验建立的多重PCR方法比传统细菌检测方法更特异、快速、灵敏,适用于肉中金黄色葡萄球菌、志贺氏菌、沙门菌和单核增生李斯特菌的快速检测。     

乳品中3种常见细菌多重PCR检测方法的建立

分别以大肠杆菌、金黄色葡萄球菌、沙门氏菌标准株为样本,提取其DNA,以大肠杆菌的pho A基因、金黄色葡萄球菌的nuc A基因和沙门氏菌的inv A基因作为靶基因,建立可以同时检测这3种菌株的多重PCR方法。与国标法对照,探讨多重PCR技术检测乳品样品中3种细菌的灵敏性和特异性。结果表明,建立的多重PCR检测方法与国标法检测的结果一致,人工模拟试验结果稳定,多重PCR具有快速、敏感和特异性强的特点。     

食品中3种致病菌多重PCR检测方法的建立及初步应用

建立用多重聚合酶链式反应(Multiplex polymerase chain reaction,mPCR)同时检测食品中沙门氏菌、金黄色葡萄球菌和单核细胞增生性李斯特菌的方法。以沙门氏菌的gyrB基因、单核细胞增生性李斯特菌的gyrB基因、金黄色葡萄球菌的coa基因作为目的基因,分别设计3对引物,通过优化反应体系,建立3种致病菌的多重PCR检测体系。采用单重PCR检测时,灵敏度可达0.423ng/mL(沙门氏菌)、2.5ng/mL(金黄色葡萄球菌)和0.36ng/mL(单核细胞增生性李斯特菌);而采用三重PCR检测时,灵敏度较单重PCR有所下降,分别为2.43ng/mL(沙门氏菌)、2.5ng/mL(金黄色葡萄球菌)、3.6ng/mL(单核细胞增生性李斯特菌)。初步建立能同时、快速、灵敏地检测食品中沙门氏菌、金黄色葡萄球菌和单核细胞增生性李斯特菌的三重PCR方法。     

牛奶中3种致病菌多重PCR的建立及初步应用

为了能同时在牛奶中快速检测金黄色葡萄球菌、大肠杆菌、沙门氏菌,本研究根据GenBank中的金黄色葡萄球菌femB、大肠杆菌phoA、沙门氏菌invA基因序列,分别设计3对特异性引物(目的片段分别为233 bp、444 bp、724 bp),通过对PCR反应条件的优化建立了多重PCR方法。敏感性、特异性试验结果显示,该多重PCR对金黄色葡萄球菌、大肠杆菌、沙门氏菌的最低核酸检测量分别为13.3 pg/mL、13.3 pg/mL、133.3 pg/mL,而对牛结核杆菌、多杀性巴氏杆菌、牛支原体、单核细胞增生李斯特氏菌、志贺氏菌的扩增结果均为阴性。对25分临床样品的检测结果表明,该多重PCR检测结果与单一PCR检测结果一致。结果表明,建立的多重PCR方法具有很好的特异性和敏感性,可用于金黄色葡萄球菌、大肠杆菌和沙门氏菌的快速鉴别诊断。     

速冻面米制品中金黄色葡萄球菌DNA提取方法的比较分析

DNA的提取效率是影响食品中致病菌PCR检测的关键因素。以速冻面米制品中最易污染的金黄色葡萄球菌为研究对象,比较4种DNA提取方法(CTAB法、离心柱法、氨基化纳米磁珠法、羧基化纳米磁珠法)的效率和质量,对提取的DNA采用荧光定量PCR方法评价。结果表明,在三大类速冻面米制品(肉馅类、素馅类和无馅类)人工污染金黄色葡萄球菌的样品中,羧基化纳米磁珠法和氨基化羧纳米磁珠法的提取效率显著优于CTAB法和离心柱法,可推荐为速冻面米制品中金黄色葡萄球菌污染快速定量检测的DNA提取方法 。     

基于多重聚合酶链式反应和表面增强拉曼光谱技术的食源性病原菌检测模型的建立与比较

建立基于多重聚合酶链式反应(polymerase chain reaction,PCR)和表面增强拉曼光谱(surface-enhanced Raman scattering,SERS)的沙门氏菌、大肠杆菌和金黄色葡萄球菌检测模型,优化检测方案,提高食源性病原菌检测效率。以病原菌hil A、uid A和clf A的基因序列设计特异性引物,优化多重PCR反应的扩增条件,检测多重PCR的特异性和灵敏性。通过SERS技术检测3种细菌并确定检测限,对3种病原菌进行主成分分析,然后对2种方法的检测限进行比较。结果显示,建立的多重PCR和SERS技术均可特异性地检测出沙门氏菌、大肠杆菌和金黄色葡萄球菌,三重PCR反应的最低检测限为104CFU/m L,最低检出DNA量为50 pg/μL,而SERS检测沙门氏菌最低检出量为103CFU/m L,大肠杆菌和金黄色葡萄球菌的最低检出量为104CFU/m L。PCA分析的前2个主成分的累积贡献率达93. 8%。与多重PCR相比,研究建立的SERS方法提高了沙门氏菌的检测限,敏感度更高,并且缩短了检测时间,对食品中食源性病原菌的监测起到指导作用。     

多重PCR检测婴幼儿配方奶粉中3种食源性致病菌

为建立一种能够同时检测婴幼儿配方奶粉(Powdered Infant Formula,PIF)中克罗诺杆菌、沙门氏菌和金黄色葡萄球菌3种食源性致病菌的多重PCR检测方法。通过单重PCR验证了9对引物的特异性,筛选出其中3对特异性好的引物建立了多重PCR体系,对其特异性和灵敏度进行评价,并将其应用于人工污染PIF中3种食源性致病菌的检测。结果表明,针对克罗诺杆菌、沙门氏菌和金黄色葡萄球菌等3种食源性致病菌所筛选的3对引物分别能扩增出469、638和796 bp的目的条带,具有高度特异性。多重PCR检测体系的最佳退火温度为55℃,最佳Mg2+浓度为2.00 mmol/L,最佳引物浓度为400 nmol/L。在此条件下3种目的菌在102 CFU/mL均可同时扩增出较清晰条带。将建立的多重PCR检测体系应用于人工污染PIF中3种食源性致病菌的检测,其检出限达到103 CFU/g。本研究初步建立了一种能准确、快速、特异性的检测PIF中克罗诺杆菌、沙门氏菌和金黄色葡萄球菌的多重PCR方法,适用于PIF中3种常见的食源性致病菌的快速检测。     

多重PCR同时检测食品中4 种细菌与常见霉菌

建立一种同时检测食品中金黄色葡萄球菌、单核细胞增生李斯特氏菌、沙门氏菌、大肠杆菌O157:H7以及霉菌的多重聚合酶链式反应（polymerase chain reaction,PCR）检测方法。根据金黄色葡萄球菌的耐热核酸酶基因（nuc）、沙门氏菌的侵袭正调节蛋白基因（hilA）、大肠杆菌O157:H7鞭毛基因（flic）、单核细胞增生李斯特氏菌的毒力调控蛋白基因（prfA）及霉菌18S?rRNA基因V5区分别设计5?对特异性引物,并对PCR扩增反应体系和扩增条件进行优化,确定获得特异性良好的PCR扩增产物。而后在37?℃对人工污染致病菌的香肠、面包和豆腐进行增菌培养,5?种致病微生物在20?h内的检出限均可达到100?CFU/25?g。本实验建立的多重PCR检测方法适用于食品中4?种细菌与常见霉菌的同时检测,相较于传统检测方法,具有快速、简便、特异性高的优点。     

Construction and evaluation of a microbiological positive process internal control for PCR-based examination of food samples for Listeria monocytogenes and Salmonella enterica

PCR assays for food-borne pathogens are widely available but have had more limited application to food testing compared with their use in clinical laboratories. When testing food samples, false negative PCR results can occur and may be due to interference with target-cell lysis necessary for nucleic acid extraction, nucleic acid degradation and/or direct inhibition of the PCR. Therefore, it is essential to include appropriate controls for the application of PCR to the detection of pathogens in food samples. The purpose of this study was to develop and evaluate a novel internal control (IC), capable of monitoring the complete detection procedure, from DNA extraction through to amplification and detection. A 'positive process' IC was developed for the reliable application of real-time PCR assays for the detection of Salmonella enterica or Listeria monocytogenes in enrichment broths. Two novel real-time 5' nuclease PCR assays for the detection of a 77 bp fragment of the green fluorescent protein (gfp) gene and a 91 bp fragment of the iroB gene of S. enterica were developed. These assays were specific and had detection limits of 5+/-0.88 and 15+/-1.03 CFU per PCR for the gfp and iroB genes respectively. The gfp PCR assay was combined with the iroB PCR assay, and also with a previously published real-time 5' nuclease PCR assay for the detection of the hlyA gene of L. monocytogenes. Duplexed assays were optimised such that the target genes were simultaneously amplified at similar sensitivities to single reactions. The gfp gene was cloned into the chromosome of a non-pathogenic strain of Escherichia coli and the modified strain successfully encapsulated in LENTICULE discs. A single disc was added to 1 ml of standard enrichment broths immediately prior to DNA extraction, and used as an IC for the detection of L. monocytogenes and S. enterica by PCR. This method was evaluated using 393 naturally contaminated food or environmental samples, 267 for the detection of Salmonella spp. and 126 for Listeria spp. PCR inhibition was detected in 29 (8%) extracts, although neither pathogens were detected in these broths by culture. S. enterica was detected by PCR in 43 of 45 (96%) broths that were positive by conventional culture. The iroB gene was also detected in a further 2 broths by PCR alone. L. monocytogenes was detected in 6 broths by both PCR and conventional culture, plus an additional 7 by PCR only. Control strategies such as those described here are important tools for the interpretation of PCR assays by improving the reliability of detection of pathogens in food.     

A multiplex RTi-PCR reaction for simultaneous detection of Escherichia coli O157:H7, Salmonella spp. and Staphylococcus aureus on fresh, minimally processed vegetables

In this work, a new multiplex single-tube real-time PCR approach is presented for the detection of Escherichia coli O157:H7, Salmonella spp. and Staphylococcus aureus, three of the more frequent food-borne bacterial pathogens that are usually investigated in a variety of food matrices. The study includes the design and specificity testing, of a new primer and probe specific for Salmonella spp. Reaction conditions were adjusted for the simultaneous amplification and detection of specific fragments in the beta-glucuronidase (uidA, E. coli) and Thermonulease (nuc, Sta. aureus) genes, and in the replication origin sequence (oriC, Salmonella spp.). Melting-curve analysis using a SYBR Green I RTi-PCR approach showed characteristic T(m) values demonstrating the specific and efficient amplification of the three fragments. Subsequently, a TaqMan RTi-PCR approach was settled, using FAM, NED and VIC fluorescently labelled specific probes for an automated detection. It was equally sensitive than uniplex RTi-PCR reactions in Sta. aureus and E. coli O157:H7, using same amounts of purified DNA, and allowed detection of 10 genome equivalents in the presence of 10(2) or 10(4) genome equivalents of the other two pathogens. Finally, it was tested in artificially inoculated fresh, minimally processed vegetables, revealing a sensitivity of 10(3)CFUg(-1) each of these pathogens in direct detection, following DNA extraction with DNeasy Tissue Kit (Qiagen). The multiplex RTi-PCR developed scored the sensitivity recognised for PCR in food and it allows a high-throughput and automation, thus it is promising as a rapid and cost-effective test for the food industry.     

多重PCR检测4种常见食源性致病菌

目的 建立一种多重聚合酶链式反应法(multiplex polymerase chain reaction, MPCR)快速检测肉制品中金黄色葡萄球菌、沙门氏菌、志贺氏菌和单增李斯特氏菌的分析方法。方法 选取金黄色葡萄球菌nuc基因、沙门氏菌SipB基因、志贺氏菌ipaH基因、单增李斯特菌inlA基因作为目标基因, 设计4对PCR引物, 建立并优化多重PCR反应体系, 评价该体系的特异性和灵敏度, 并对人工污染的熟肉样品进行检测。结果 构建的多重PCR方法特异性强、灵敏度高, 人工污染熟肉匀浆中4种致病菌的检出限为103 CFU/mL。结论 构建的多重PCR检测方法能够快速、准确、高效地检测肉制品中金黄色葡萄球菌、沙门氏菌、志贺氏菌和单增李斯特氏菌, 为食源性疾病菌的快速检测提供参考依据。     

食品检测用4种病原菌基因组试剂盒提取方法的比较与优化

目的:采用国产的天根细菌基因组提取试剂盒,制备具有自主知识产权的、达到国家核酸标准物质要求的食源性病原菌的基因组样品。方法:以4种食源性病原菌大肠埃希氏菌O157:H7、单增李斯特氏菌、肠炎沙门氏菌和金黄色葡萄球菌为研究对象,首先使用进口OMEGA细菌基因组提取试剂盒和国产天根细菌基因组提取试剂盒提取4种病原菌的基因组,然后对国产试剂盒提取的基因组浓度和纯度较低的大肠埃希氏菌O157:H7、肠炎沙门氏菌和金黄色葡萄球菌的基因组提取方法进行优化。最后对4种病原菌基因组的完整性和纯度进行琼脂糖凝胶电泳检测,并分别对4种病原菌的特征毒力基因进行PCR扩增验证。结果:通过方法优化,使用国产天根细菌基因组提取试剂盒提取的4种病原菌的基因组质量浓度均在50 ng/μL以上,A260/A280和A260/A230的值在1.7~2.0之间,基因组DNA条带完整,无RNA和蛋白污染,各菌株的特征毒力基因均为阳性。结论:通过基因组提取方法的优化,得到符合国家核酸标准样品要求的4种病原菌基因组样品,为后续大量制备核酸标准样品奠定了基础。     

食品中沙门菌PCR检测方法的建立

为建立食品中快速检测沙门菌的PCR方法。选取沙门菌属侵袭性抗原保守基因invA基因上的靶序列设计一对引物,选择最适Mg 浓度和退火温度,建立最适PCR反应体系,用2%琼脂糖,5μl反应产物(包括EB),100V,40min进行电泳,显像。用该引物对已经传统方法鉴定的22种77株沙门菌和24种24株非沙门菌进行特异性检测,并对人工污染的食品进行检测条件的研究。Mg 浓度和退火温度对该反应体系的影响较小,稳定性较好;经传统方法鉴定的22种77株沙门菌和24种24株非沙门菌验证了该检验方法具有很好的特异性;该检测方法可以在19h内检出含有沙门菌102CFUg的食品(火腿肠、鸡蛋、散装肉馅)。与传统方法比较,该方法快速、敏感、特异,能在较短的时间内对大量样品同时进行检测,适用于食品中沙门菌的快速、敏感、特异检测。     

IMS USING IN-HOUSE MONOCLONAL ANTIBODY-COATED MAGNETIC BEADS ASSOCIATED TO PCR ASSAY FOR DETECTION OF SALMONELLA TYPHIMURIUM IN RAW MEATS

An immunomagnetic separation (IMS) technique and a PCR assay were developed for use in detection of Salmonella Typhimurium in meat samples. To prevent false-negative results, an internal amplification control was developed. The polymerase chain reaction (PCR) using primers specific for an omp gene sequence of Salmonella spp has shown 100% sensitivity and specificity and a detection limit of 10⁴ cfu/mL. The IMS-PCR methods using PCR immediately after IMS and using 6 h postenrichment in brain heart infusion between IMS and PCR resulted in detection limits of 10³ cfu/mL and 1–10 cfu/mL, respectively. The lowest level of S. Typhimurium that could be detected by the IMS-PCR method in the presence of natural microbiota from inoculated meat samples was 1–10 cfu/25 g. When samples were analyzed using enrichment protocols without IMS, several false-negative results were obtained.

PRACTICAL APPLICATIONS

The immunomagnetic separation-polymerase chain reaction (IMS-PCR) method developed enabled a rapid and sensitive detection of Salmonella Typhimurium in inoculated meat samples. Monoclonal antibody (Mab)-coated magnetic beads prepared in-house were efficient in concentrating and separating the bacteria from the food matrix, thus improving detection limit and avoiding false-negatives. The internal amplification control (IAC), now mandatory in PCR assays, using the same primers of the target DNA further prevented false-negative results. Therefore, the IMS-PCR method developed in this study could be used in the future by the Brazilian food industry as a substitute for the expensive imported kits for Salmonella detection in foods. We are now developing a panel of Mabs against conserved antigens of Salmonella for use in the IMS-PCR method in order to extend its applicability for detection of other serovars.     

食品中金黄色葡萄球菌多重PCR检测方法的研究

以耐热核酸酶基因nuc、纤维蛋白原结合蛋白基因clfA和SmaI限制性酶切片段特异序列为靶基因,设计筛选引物,建立并优化了检测金黄色葡萄球菌(Staphylococus aureus,SA)的多重PCR体系。采用10株SA和46株非SA验证了该多重PCR具有很好的特异性。PCR检测的灵敏度在DNA水平上达到1.197 3 ng。人工污染样品,当起始污染量为1.2个/g时,37℃增菌培养6 h即可检出。一共检测了43份样品,检出3份阳性样品,其中有2份阳性样品与传统方法一致,另外一份阳性样品用测序验证。作者建立的多重PCR方法可特异、快速地实现对SA的检测。