多重PCR技术在食源性致病菌检测中应用的研究进展

食源性致病菌的多重PCR检测技术是指能够同时扩增得到同种或多种致病菌的不同基因片段的技术。因该技术特异、灵敏且分析效率高,现已被广泛应用于食源性致病菌的检测工作中。本文介绍了多重PCR在食源性致病菌检测中应用的研究近况,并对影响因素及存在的问题进行了阐述。      

Taqman荧光探针技术在食源性致病菌检测中的应用

Taqman荧光探针技术作为定量PCR的代表性方法,综合了PCR技术及荧光标记技术,由引物和探针双重控制靶基因的选择,具有很好的特异性和灵敏度。近年来该技术逐步应用于食品中致病微生物的检测。本文概述了Taqman荧光探针技术的原理、优缺点及其在食源性致病菌检测中的应用与研究进展,并对其应用前景进行了探讨。      

哈密瓜中青霉菌产细胞壁降解酶的条件及致病机理初步研究

以哈密瓜中青霉病原菌为研究对象,从培养时间、温度、起始pH、碳源和氮源几方面进行单因素实验,再设计正交实验对其产细胞壁降解酶的条件进行优化。旨在研究青霉病原菌产细胞壁降解酶的种类及其产酶的最佳优化条件,为进一步研究青霉病原菌产细胞壁降解酶对哈密瓜的致病作用奠定一定的基础。结果表明,在离体培养条件下产生的多聚半乳糖醛酸反式消除酶(PGTE)和果胶甲基反式消除酶(PMTE)两种酶活性均较低,病原菌产纤维素酶(Cx)最佳优化条件:培养时间为4d,培养基起始pH为6.5,碳源浓度为1.5%,氮源浓度为1.0%,此最佳优化条件下Cx的酶活性为358.12U/mg。      

Inactivation of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on spinach leaves by X-ray

Several recent foodborne disease outbreaks associated with leafy green vegetables, including spinach, have been reported. X-ray is a non-thermal technology that has shown promise for reducing pathogenic and spoilage bacteria on spinach leaves. Inactivation of inoculated Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica and Shigella flexneri on spinach leaves using X-ray at different doses (0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 1.5 and 2.0 kGy) was studied. The effect of X-ray on color quality and microflora counts (mesophilic counts, psychrotrophic counts and yeast and mold counts) of untreated and treated spinach was also determined. A mixture of three strains of each tested organism was spot inoculated (100 μl) onto the surface of spinach leaves (approximately 8–9 log ml⁻¹), separately, and air-dried, followed by treatment with X-ray at 22 °C and 55–60% relative humidity. Surviving bacterial populations on spinach leaves were evaluated using a nonselective medium (tryptic soy agar) with a selective medium overlay for each bacteria; E. coli O157:H7 (CT-SMAC agar), L. monocytogenes (MOA), and S. enterica and S. flexneri (XLD). More than a 5 log CFU reduction/leaf was achieved with 2.0 kGy X-ray for all tested pathogens. Furthermore, treatment with X-ray significantly reduced the initial inherent microflora on spinach leaves and inherent levels were significantly (p < 0.05) lower than the control sample throughout refrigerated storage for 30 days. Treatment with X-ray did not significantly affect the color of spinach leaves, even when the maximum dose (2.0 kGy) was used.     

基因芯片法与常规检测法在食源性疾病中的应用对比分析

目的对比分析基因芯片法与常规检测法在食源性疾病中的应用效果。方法收集2016年4月到2018年8月收治的诊断为食源性疾病的患者98例为研究对象,收集患者的新鲜粪便,根据检测方法不同分为对照组与观察组,观察组应用基因芯片法进行病原菌的检测,对照组则应用常规培养法进行病原菌的检测。,观察比较两组的病原菌检测阳性率和检测时间等相关指标。结果在98例患者中,观察组采用基因芯片法检测出病原菌58例(副溶血弧菌9例,痢疾杆菌32例,沙门菌10例,大肠埃希菌2例,金黄色葡萄球菌5例),病原菌检出率为58.2%。对照组采用常规培养法检测出病原菌32例(副溶血弧菌5例,痢疾杆菌19例,沙门菌4例,金黄色葡萄球菌4例),病原菌检出率为32.7%。基因芯片法和培养法对病原菌、痢疾杆菌的检出率差异存在统计学意义(P0.05)。观察组采用基因芯片法用于食源性疾病患者的病原菌检测时间明显短于常规培养法,差异有统计学意义(P0.05)。结论基因芯片技术能够快速检出食源性疾病病原菌,可以替代常规培养法对病原菌进行检测,在食源性疾病的早期诊断和治疗中具有重要的临床价值。     

The mitochondrial genome from the thermal dimorphic fungus Paracoccidioides brasiliensis

We present here the sequence of the mitochondrial DNA of the pathogenic thermodimorphic fungus Paracoccidioides brasiliensis, agent of an endemic disease in most South American countries. The sequenced genome has 71 334 bp and is organized as a circular molecule with two gaps of unknown size flanking the middle exon of the nad5 gene. We located genes coding for the three subunits of the ATP synthase (atp6, atp8 and atp9), the apocytochrome b (cob), three subunits of the cytochrome c oxidase enzyme complex (cox1, cox2 and cox3), seven subunits of the reduced nicotinamide adenine dinucleotide ubiquinone oxidoreductase (nad1, nad2, nad3, nad4, nad5, nad6 and nad4L) and the large (rnl) and small (rns) subunits of ribosomal RNA. Two maturases and a ribosomal protein (rms5) are located inside introns. Twenty-five tRNAs were identified with acceptors for all 20 amino acids. Seven polypurine/polypyrimidine tracts (140-240 bp) have been found in this genome. All genes are in the same orientation over the genome, while their order is closest to the mitochondrial genomes from Penicillium marneffei and Aspergillus nidulans.     

Enhanced antimicrobial activity of nisin-loaded liposomal nanoparticles against foodborne pathogens

This study was designed to evaluate the prolonged antimicrobial stability of nisin-loaded liposome (LipoN) nanoparticles against Listeria monocytogenes and Staphylococcus aureus. The sizes of bare liposomes and LipoN were uniformly distributed between 114 and 125 nm. The nanoparticles were homogeneously dispersed in water with less than 0.2 of polydispersity index. The zeta potential value of LipoN was +17.1 mV due to the positive charged nisin, attaining 70% of loading efficiency. The minimum inhibitory concentration of LipoN against L. monocytogenes and S. aureus was 320 international unit/mL. The LipoN significantly enhanced the antimicrobial stability in brain heart infusion agar compared to free nisin. The numbers of L. monocytogenes and S. aureus exposed to LipoN were effectively reduced by more than 6 log colony-forming unit/mL after 48 and 72 h of incubation, respectively. These results provide useful information for the development of antimicrobial delivery system to improve food safety.     

阻抗法在食品微生物快速检测中的应用

阻抗法作为一种高效的微生物快速检测方法,在食品工业中具有广泛的应用前景。文章介绍了阻抗法检测微生物的原理及其在检测菌落总数、酵母菌、大肠杆菌、金黄色葡萄球菌、沙门氏菌以及商业无菌等方面的应用。     

广州市白云口岸航空食品中金黄色葡萄球菌凝固酶基因分型及肠毒素基因研究

目的对2013—2015年从广州市白云口岸航空食品中分离的金黄色葡萄球菌进行基因分型研究,为食源性金黄色葡萄球菌分子溯源提供基础数据。方法以血浆凝固酶和肠毒素为目标基因,采用聚合酶链式反应(PCR)方法对9株金黄色葡萄球菌进行基因分型,其中6株为航空食品分离株,1株为配餐车间大门手拭分离株,2株为标准菌株。肠毒素基因检测包括5种传统肠毒素基因(sea、seb、sec、sed、see)和6种新型肠毒素基因(ser、seg、seh、sei、sej、sep)。结果 6株航空食品分离株的血浆凝固酶基因扩增分型结果为2个PCR型,酶切后得3种亚型;肠毒素基因检测结果显示有2株航空食品分离株含有肠毒素基因,检出率为33.3%(2/6),检出的基因为2种传统肠毒素基因(sec、sed)和4种新型肠毒素基因(ser、seg、sei、sej),均同时携带2种以上肠毒素基因。结论血浆凝固酶基因扩增分型结果显示,不同时间、不同采集地点存在相同的基因型,提示金黄色葡萄球菌存在交叉污染的可能性;航空食品分离株共检出6种肠毒素基因,提示金黄色葡萄球菌基因型多样性,应加强其他新型肠毒素基因检测。     

DNA微阵列在食品营养与安全中的应用与展望

DNA微阵列是一种高通量基因检测和分析技术,主要概括介绍DNA微阵列在营养基因组学、食源性病原体检测、转基因食品和饮食补充剂安全性评价中的应用。