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1.
目的建立多重PCR法检测产志贺毒素性大肠杆菌(shiga toxin-producing Escherichia coli, STEC)主要血清型O26、O145、O45和O121的分析方法。方法根据GenBank登录序列,设计扩增O抗原翻转酶(wzx)基因的引物,建立PCR方法,并以STECO26、O145、O45和O121基因组为模板,检验多重PCR的灵敏度和特异性。使用建立的PCR,检测牛胴体表面拭子,阳性扩增条带送测序,以验证PCR扩增的可靠性。同时将阳性扩增样品,涂布显色平板,分离靶标血清型细菌。结果本研究成功建立STEC O26、O145、O45和O121的多重PCR方法, PCR循环参数中退火温度为60℃,扩增片段分别为249、353、890和587 bp。多重PCR直接检测O26、O145、O45和O121时,最低检测限介于10~3～10~4 CFU/mL,而增菌后再检测,最低检测限均为1CFU/m L。多重PCR用于其他血清型STEC,和非大肠杆菌扩增时,均未扩增出目的条带,只有O26、O145、O45和O121能够扩增出相应条带。当使用多重PCR直接检测胴体擦拭子时,阳性率为5.45%(3/55),主要为O26、O145血清型;增菌后检测阳性率为7.27%(4/55),主要为O26、O145和O121血清型。阳性PCR扩增样品,成功分离到O26两株、O145和O121各一株。分离菌株具有典型大肠杆菌的生化特性,携带STEC代表性毒力因子志贺毒素和紧密素,且具有多重耐药性。结论以STECO26、O145、O45和O121的wzx基因为检测靶标,成功建立多重PCR方法,灵敏度和特异性良好,与细菌分离联合使用,可减少工作量,精准分离目的病原菌。 相似文献
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The survival and growth of Salmonella spp., Escherichia coli O157:H7, Listeria monocytogenes , and Staphylococcus aureus on peeled Hamlin orange were examined. Fruits were peeled by infusing the peel with water to assist hand removal. The peeled oranges had an average pH of 6.0–6.5 at the surface and 3.8 in the juice. After surface inoculation, peeled fruits were incubated for up to 14 days. Growth was observed with all tested pathogens only at the abusive storage temperature (24°C). Refrigeration (4 or 8°C) effectively inhibited the growth of all pathogens and caused population reduction of Salmonella spp. and S. aureus. 相似文献
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Corliss A. O'Bryan Philip G. Crandall Elizabeth M. Martin Carl L. Griffis Michael G. Johnson 《Journal of food science》2006,71(3):R23-R30
ABSTRACT: The heat-resistance data in meat and poultry for various strains of Salmonella, Listeria monocytogenes , and Escherichia coli O157:H7 as well as Listeria innocua M1 are summarized. Heat resistance of these organisms is affected by many factors. Different strains of the same organism have different responses to heat. Heat resistance can also be influenced by the age of the culture, growth conditions, pH, and numerous other factors. Data from this review may prove useful to processors in validating their times and temperatures for thermal processing of meat and poultry. The obvious gaps in the data will provide researchers opportunities to fill those gaps. In addition, it will encourage the development of surrogates, whether biological or otherwise, that will be able to be used in an actual processing environment. 相似文献
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This study compared biofilm formation by 7 serogroups of pathogenic Escherichia coli and 2 or 3 phenotypes of Salmonella (susceptible, multidrug‐resistant [MDR], and/or multidrug resistant with ampC gene [MDR‐AmpC]). One‐week mature biofilms were also exposed to water, quaternary ammonium compound‐based (QAC), and acid‐based (AB) sanitizers. Seven groups (strain mixture) of above‐mentioned pathogens were separately spot‐inoculated onto stainless steel coupons surfaces for target inoculation of 2 log CFU/cm2, then stored statically, partially submerged in 10% nonsterilized meat homogenate at 4, 15, and 25 °C. Biofilm cells were enumerated on days 0, 1, 4, and 7 following submersion in 30 mL for 1 min in water, QAC, and AB. Counts on inoculation day ranged from 1.6 ± 0.4 to 2.4 ± 0.6 log CFU/cm2 and changed to 1.2 ± 0.8 to 1.9 ± 0.8 on day 7 at 4 °C with no appreciable difference among the 7 pathogen groups. After treatment with QAC and AB on day 7, counts were reduced (P < 0.05) to less than 0.7 ± 0.6 and 1.2 ± 0.5, respectively, with similar trends among pathogens. Biofilm formation at higher temperatures was more enhanced; E. coli O157:H7, as an example, increased (P < 0.05) from 1.4 ± 0.6 and 2.0 ± 0.3 on day 0 to 4.8 ± 0.6 and 6.5 ± 0.2 on day 7 at 15 and 25 °C, respectively. As compared to 4 °C, after sanitation, more survivors were observed for 15 and 25 °C treatments with no appreciable differences among pathogens. Overall, we observed similar patterns of growth and susceptibility to QAC and AB sanitizers of the 7 tested pathogen groups with enhanced biofilm formation capability and higher numbers of treatment survivors at higher temperatures. 相似文献
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Wladir B. Valderrama Edward G. Dudley Stephanie Doores 《Critical reviews in food science and nutrition》2016,56(9):1519-1531
Generally, the enumeration and isolation of food-borne pathogens is performed using culture-dependent methods. These methods are sensitive, inexpensive, and provide both qualitative and quantitative assessment of the microorganisms present in a sample, but these are time-consuming. For this reason, researchers are developing new techniques that allow detection of food pathogens in shorter period of time. This review identifies commercially available methods for rapid detection and quantification of Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and Shiga toxin-producing Escherichia coli in food samples. Three categories are discussed: immunologically based methods, nucleic acid-based assays, and biosensors. This review describes the basic mechanism and capabilities of each method, discusses the difficulties of choosing the most convenient method, and provides an overview of the future challenges for the technology for rapid detection of microorganisms. 相似文献
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Whey protein isolate (WPI) films (pH 5.2) containing 0.5 to 1.0% p‐aminobenzoic acid (PABA) and/or sorbic acid (SA) were assessed for antimicrobial and mechanical properties while in contact with sliced bologna and summer sausage that were inoculated with Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica subsp. enterica serovar Typhimurium DT104. WPI films containing SA or PABA decreased L. monocytogenes, E. coli, and S. Typhimurium populations by 3.4 to 4.1,3.1 to 3.6, and 3.1 to 4.1 logs, respectively, on both products after 21 d at 4 °C. Background flora was inhibited compared with controls. Film tensile strength decreased while % elongation remained unchanged following 72 h of product contact. 相似文献
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目的了解江门市区2004-2008年食品中沙门菌、金黄色葡萄球菌、单核细胞增生李斯特菌、副溶血性弧菌及肠出血性大肠肝菌(EHEC)O157∶H7的污染状况,确定上述致病菌可能污染的高危食品,为食源性疾病监测提供科学依据。方法依据国标方法,并按《广东省食源性致病菌监测计划》检测技术要求,对采集的食品样本分别进行沙门菌、金黄色葡萄球菌、单核细胞增生李斯特菌、副溶血性弧菌及EHECO157∶H7分离、生化及血清学鉴定。结果从9类626份食品中,5年共检出致病菌54株,总检出率为8.63%。其中金黄色葡萄球菌3年检出14株,检出率最高为4.83%;其次为沙门菌5年检出23株,检出率为3.67%;单核细胞增生李斯特菌5年检出16株,检出率为2.56%;副溶血性弧菌5年中仅检出1株,检出率为0.16%;未检出EHECO157∶H7。以非定型包装熟肉、生肉类污染较为严重。结论应加强非定型包装熟肉和生肉类食品食源性致病菌污染的监测。 相似文献
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ABSTRACT: Pathogens on edible plants present a significant potential source of human illness. From 1991 to 2002, 21% of Escherichia coli O157:H7 outbreaks were from produce-related sources. E. coli O157 and other enteric bacteria can contaminate the surface of edible plants both pre- and postharvest. Some pathogens do not survive on the leaf surface or are removed by washing, but a significant portion of these enteric pathogens can persist on the surface and proliferate. Proliferation of these dangerous pathogens can increase the likelihood of foodborne disease associated with fresh or minimally processed produce. Several intrinsic and extrinsic factors determine the ability of enteric pathogens to attach and proliferate in the phyllosphere of plants. These include motility of the pathogen, leaching of nutrients by the plant, and interaction with epiphytic organisms. The interaction of enteric pathogens with the environment can lead to internalization into tissue, incorporation into biofilms, and genetic transfer. Current produce sanitation practices can reduce the microbial load from 1 log10 to 3 log10 , so there are many new treatments possible. Understanding the ecology of enteric pathogens on plants is important to the development of sanitation methods and biocontrol agents. This knowledge can also assist the farmer in preventing contamination. With increasing consumption and importation of produce, its safety is a high priority for processors and U.S. consumers. Food safety may be markedly improved with proper attention to pathogens on edible plants. 相似文献
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The survival and growth of Vibrio cholerae O1, Salmonella typhi , and Escherichia coli O157:H7 during germination and sprouting of disinfected alfalfa seeds and alfalfa sprouts was determined. All pathogens showed ability to grow during germination and sprouting, reaching counts of approximately 6.0 log10 CFU/g after 24 h. No growth was observed for any pathogen when the sprouts were inoculated after 24 h of seed germination. At this time, the background microflora was abundant. Numbers of pathogens inoculated on alfalfa sprouts decreased less than 1 log10 CFU/g over 15 d of refrigeration. Alfalfa sprouts can be an important factor contributing to the endemicity for typhoid fever and cholera in México. 相似文献
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Eugenol and trans-cinnamaldehyde are natural compounds known to be highly effective antimicrobials; however, both are hydrophobic molecules, a limitation to their use within the food industry. The goal of this study was to synthesize spherical poly (DL-lactide-co-glycolide) (PLGA) nanoparticles with entrapped eugenol and trans-cinnamaldehyde for future antimicrobial delivery applications. The emulsion evaporation method was used to form the nanoparticles in the presence of poly (vinyl alcohol) (PVA) as a surfactant. The inclusion of antimicrobial compounds into the PLGA nanoparticles was accomplished in the organic phase. Synthesis was followed by ultrafiltration (performed to eliminate the excess of PVA and antimicrobial compound) and freeze-drying. The nanoparticles were characterized by their shape, size, entrapment efficiency, and antimicrobial efficiency. The entrapment efficiency for eugenol and trans-cinnamaldehyde was approximately 98% and 92%, respectively. Controlled release experiments conducted in vitro at 37 °C and 100 rpm for 72 h showed an initial burst followed by a slower rate of release of the antimicrobial entrapped inside the PLGA matrix. All loaded nanoparticles formulations proved to be efficient in inhibiting growth of Salmonella spp. (Gram-negative bacterium) and Listeria spp. (Gram-positive bacterium) with concentrations ranging from 20 to 10 mg/mL. Results suggest that the application of these antimicrobial nanoparticles in food systems may be effective at inhibiting specific pathogens. PRACTICAL APPLICATION: Nanoencapsulation of lipophilic antimicrobial compounds has great potential for improving the effectiveness and efficiency of delivery in food systems. This study consisted of synthesizing PLGA nanoparticles with entrapped eugenol and trans-cinnamaldehyde. By characterizing these new delivery systems, one can understand the controlled-release mechanism and antimicrobial efficiency that provides a foundation that will enable food manufacturers to design smart food systems for future delivery applications, including packaging and processing, capable of ensuring food safety to consumers. 相似文献
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ABSTRACT: Previous research with the VSV (vacuum/steam/vacuum) surface pasteurizer revealed the visceral cavity of chicken carcasses was not treated as effectively as the outside surface. The processor was modified to specifically treat the cavity by adding a mandrel assembly. Optimum process parameters were determined. Optimum process conditions were: initial vacuum 0.1s, final vacuum 0.5 s, vacuum absolute pressure of 4.1 to 7.1 kPa, steam time 0.1 s, and steam temperature 138 °C. Using carcasses inoculated with Listeria innocua and the whole bird rinse sampling procedure, bacteria kills were statistically significant at 0.7 to 0.8 log cfu/mL. Using deboned chicken breasts inoculated with L. innocua and the whole bird rinse sampling procedure, bacteria kills were statistically significant at 1.0 to 1.3 log cfu/mL. 相似文献
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CRISPR系统是一种新兴的基因编辑技术,是存在于部分细菌中的一种免疫反应系统,利用Cas基因编码的蛋白对进入细胞中的外源DNA进行高效识别并切割,保护细菌自身免受外源基因侵害。CRISPR系统主要应用于基因的定点敲入和敲除。该系统具有操作简便,适用范围广等优点,已在各类微生物和动植物中广泛应用。在CRISPR系统中,II型CRISPR系统是应用最为广泛的系统,是目前的研究热点。它包含CRISPR/ Cas9、CRISPRa和CRISPRi系统,由于CRISPRa系统目前应用较少,本文对CRISPR/ Cas9和CRISPRi系统在微生物中的应用研究现状进行综述,并对两种系统未来的发展进行展望。 相似文献
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研究了大黄对大肠杆菌、沙门氏菌和金黄色葡萄球菌的抑菌效果,初筛的结果显示大黄醇提物对这3种菌均有较强的抑菌作用,并发现其中抑菌作用最强的物质分布在大黄氯仿段萃取物中。利用UPLC-MS-MS分析大黄氯仿段萃取物,发现大黄氯仿段萃取物的主要成分分别是大黄素、芦荟大黄素、大黄酸、大黄素甲醚和大黄酚。在这五种化合物中,大黄酸对大肠杆菌和沙门氏菌具有最强的抑菌效果,对大肠杆菌和沙门氏菌的最小抑菌浓度分别为125μg/m L和250μg/m L,最小杀菌浓度分别为250μg/m L和500μg/m L,大黄素对于金黄色葡萄球菌具有较强的抑菌效果,最小抑菌浓度和最小杀菌浓度分别为62.5μg/m L和125μg/m L。 相似文献
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Osaili TM Griffis CL Martin EM Beard BL Keener AE Marcy JA 《Journal of food science》2007,72(2):M56-M61
ABSTRACT: Decimal reduction times ( D -values) and thermal resistance constants ( z -values) for 3 foodborne pathogenic bacteria in formulated ready-to-eat breaded pork patties were determined with thermal inactivation studies. Meat samples, inoculated with Escherichia coli O157:H7, Salmonella , and Listeria monocytogenes cultures or uninoculated controls, were packaged in sterile bags, immersed in circulated water bath, and held at 55, 57.5, 60, 62.5, 65, 67.5, and 70 °C for different durations of time. The D - and z -values were determined by using a linear regression model. Average calculated D -values for E. coli O157:H7, Salmonella , and L . monocytogenes at a temperature range of 55 to 70 °C were 32.11 to 0.08 min, 69.48 to 0.29 min, and 150.46 to 0.43 min, respectively. Calculated z -values for E. coli O157:H7, Salmonella , and L. monocytogenes were 5.4, 6.2, and 5.9 °C, respectively. The results of this study will be useful to food processors to validate thermal lethality of the studied foodborne pathogens in ready-to-eat breaded pork patties. 相似文献
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人工合成的仿生鲶鱼抗菌肽DNA序列,经聚合酶链式反应(PCR)扩增后得到带有不同限制性酶切位点的序列XH1、XH2、XH3．将此基因克隆至载体pGEX-5X-3,成功构建了三串联的重组质粒．测序验证后转化大肠杆菌BL21(DE3),37℃IPTG诱导,获得高效表达,SDS—PAGE扫描分析表明,融合蛋白可达细菌全蛋白总量的30％,融合蛋白以包含体的形式存在于大肠杆菌细胞中． 相似文献
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目的建立食品中的沙门氏菌、副溶血性弧菌、大肠埃希氏菌O157:H7、金黄色葡萄球菌和单核细胞增生李斯特氏菌的PCR快速检测方法。方法以缓冲蛋白胨水为增菌培养基,采用直接提取法提取DNA并测定其核酸浓度。对PCR的退火温度、模板浓度进行优化,把5种目标菌分为两组进行检测分析,并进行特异性和灵敏度实验。结果 5种目标菌培养后均表现出良好的生长趋势。PCR扩增最佳退火温度为59℃, 5种目标菌的引物特异性好,方法的检测灵敏度高。沙门氏菌、副溶血性弧菌、大肠埃希氏菌O157:H7、金黄色葡萄球菌和单核细胞增生李斯特氏菌最低检出核酸浓度分别为0.0202、0.158、0.187、2.30和1.05μg/mL。结论该方法简便、快速、灵敏度高,能满足食品安全检测要求。 相似文献
19.
柯振华 《食品安全质量检测学报》2020,11(19):6855-6861
目的建立叠氮丙啶-定量聚合酶链反应法(propidiummonoazide-quantitativepolymerasechain reaction,PMA-qPCR)快速检测餐饮食品中6病原菌的方法。方法开发6种病原菌前增菌通用型培养基,采用热裂解方法提取样品DNA,采用PMA技术鉴别活菌与死菌,运用分子生物学技术检测样品中目标菌的特异性基因片段,建立病原菌的PMA-qPCR检测方法,开展餐饮食品样品病原菌筛查检测。结果本方法特异性良好,灵敏度较高, 1533份餐饮食品样品中检出病原菌71株,检出率为4.63%(71/1533)。结论本研究运用PMA-qPCR开展病原菌活菌检测技术研究,所建立研究方法可广泛应用于餐饮食品及相关食品中病原菌的快速筛查检测,具有较好的应用前景和现实意义。 相似文献
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M.G. SMITH 《Journal of food science》1995,60(3):509-512
Predictive microbiology requires a sound basis of observed results, and factors that contribute to death of bacterial cells, before accurate equations can be developed. The effect of chilling and freezing strains of Escherichia coli and salmonella serotypes in nutrient broth, a noninhi-bitory liquid medium, was investigated. The phase of growth, small changes in composition of test medium, and sub-cultures made after primary isolation, influenced survival. Therefore, such influences must be considered when attempting to extrapolate results Erom pure cultures on laboratory media, to predict behavior of similar organisms in foods during chilling and freezing. 相似文献