冷却肉中单核增生李斯特氏菌的抑菌研究

紫外线对于单核增生李斯特氏菌悬液有较好的杀菌效果,照射5 min即可将全部菌体杀死。柠檬酸、乳酸抑菌效果好,其含量达到2 mL/L,可抑制李斯特氏菌的生长。有机酸钠盐的抑菌效果较差。丁香、肉桂、大蒜、生姜精油对于李斯特氏菌有较好的抑菌作用,这4种精油复配后存在协同抑菌作用。     

单核增生李斯特氏菌生物被膜的形成及控制

研究温度、接种量对单核增生李斯特氏菌(Listeri amonocytogenes)生物被膜形成的影响和肉制品加工企业中常用的消毒方法对单增李斯特氏菌生物被膜的去除及抑制作用.研究结果表明,单核增生李斯特氏菌标准菌株生物被膜的形成主要受到温度的影响,接种量对生物被膜形成的影响只在特定的温度范围内显著.以不同的常规消毒方法对模拟生产车间条件培养生长1d的单增李斯特氏菌生物被膜进行处理,结果发现不同方法对生物被膜去除效果的差异性随着处理天数的增加而增加,且各方法对生物被膜的去除作用与抑制作用无关.     

MPCR检测食品中大肠杆菌O157和单核增生李斯特氏菌的研究

根据大肠杆菌O157(Escherichia coli O157,E. coli O157)的志贺样毒素基因slt和“黏附抹平”因子eaeA基因、单核增生李斯特氏菌(Listeria monocytohenes,LM)的编码溶血素O的hlyA基因和毒力基因plcA,分别设计上游和下游的slt、eaeA、hlyA和plcA四对引物,对应扩增片段依次为780、450、708、600bp。通过对单管多重PCR(multiplex PCR,MPCR)扩增的特异性、敏感性分析以及对单管多重PCR扩增条件,如Mg2+浓度、dNTPs浓度和退火温度等的优化,建立快速检测大肠杆菌O157和单增李斯特菌的多重PCR方法,该方法能同时检测到0.50ng的E. coliO157和单增李斯特菌基因组DNA,并且操作简便、快速,具有良好的敏感性和特异性,能够快速实现对食品中多种致病菌的诊断和监控。     

进出境食品中单核增生李斯特氏菌的血清分型与脉冲场凝胶电泳分型分析研究

目的 研究进出境食品中的单核增生李斯特氏菌（LMO）的血清分型与脉冲场凝胶电泳分型的特性及其关系。方法 采用标准方法对39株分离的LMO进行PFGE分型,分别用ApaI和Asc I酶切,电泳图谱进行聚类分析,以上菌株同时进行血清分型检测。结果 39株LMO分成6个血清型;经ApaI酶切后,分成29种带型,相似度在57.4%~100%;Asc I酶切后,分成34种带型,相似度在48.6%~100%。讨论 AscI酶切的PFGE分离效果优于ApaI酶切,与血清分型的一致性低于ApaI酶切;PFGE分型效果优于血清分型。     

进出境食品中单核增生李斯特菌的血清分型与脉冲场凝胶电泳分型分析

目的研究进出境食品中的单核增生李斯特菌(LMO)的血清分型与脉冲场凝胶电泳(PFGE)分型的特性及其关系。方法采用标准方法对39株分离的LMO进行PFGE分型,分别用ApaI和Asc I酶切,电泳图谱进行聚类分析,以上菌株同时进行血清分型检测。结果 39株LMO分成6个血清型;经ApaI酶切后,分成29种带型,相似度在57.4%～100%;Asc I酶切后,分成34种带型,相似度在48.6%～100%。讨论 AscI酶切的PFGE分离效果优于ApaI酶切,与血清分型的一致性低于ApaI酶切;PFGE分型效果优于血清分型。     

单核增生李斯特氏菌近红外快检方法建立与应用

目的建立一种近红外荧光免疫法快速检测单增李斯特氏菌的方法。方法采用近红外荧光染料Dylight800标记单增李斯特菌单克隆抗体,结合免疫侧向流技术制备单增李斯特菌快速检测试纸条。结果整个实验过程仅需45 min,对食品中单增李斯特氏菌最低检测限为500 CFU/mL,与其他5种食源性致病菌均无交叉反应。特异性为89.47%,敏感性为100%。采用近红外荧光免疫层析法和传统方法对30份食品进行检测,结果发现2种方法符合性达93.3%。结论所研制的单增李斯特菌的近红外快检试纸条具有特异性、敏感性较高的特点,适用于食品样本中单增李斯特菌的即时检测。     

CodY在单核细胞增生李斯特菌抗氧化胁迫中的作用

目的:探究全局性转录调控因子CodY在单核细胞增生李斯特菌(Listeria monocytogenes,Lm)抗氧化应激中的作用.方法:利用H2O2对处于对数中期(OD600 nm=0.65)的Lm野生株EGDe和CodY缺失株EGDe△codY进行氧化胁迫,比较两菌株氧化耐受能力、抗氧化应激物(过氧化氢酶(cata...     

单核细胞增生李斯特菌菌膜形成突变株的筛选

通过对功能和调控基因的研究,探讨单核细胞增生李斯特菌菌膜的形成机制,建立防治该细菌污染食品的方法.使用电转化的方法,将携带转座子Tn917的质粒pTV1-OK转化到单核细胞增生李斯特菌中,诱导转座,获得1 880个突变株,加上前期构建的突变株,使突变库增加到2 200株.使用96孔细胞培养板对随机挑选的1 000余株突变株进行菌膜培养,结晶紫染色后测OD595值.以此值作为菌膜形成量的筛选依据,最终挑选出菌膜形成能力变小的突变株8株.目标突变获得率约8‰.对筛选的菌膜形成量变小的突变株进行荧光显微现察,证实该8株突变株菌膜形成能力弱于野生菌株.通过PCR验证,这8株突变株的基因组中插入了Tn917,这可能是它们的表型发生变化的原因.     

牛乳中单核细胞增生李斯特菌的分离与鉴定

牛乳中单核细胞增生李斯特菌的分离与鉴定唐敏莉，刘敏娟，孙钊，黄金文（齐齐哈尔市卫生防疫站）前言李斯特菌是引起人、畜单核细胞增生的一种致病菌，已逐渐被人们注意，世界卫生组织１９８８年报告，在乳及乳制品、肉类、禽类等食品中均发现李斯特菌的存在［１］．近年...     

Listeria monocytogenes: Occurrence in beef and identification of the main contamination points in processing plants

This study aimed to establish the occurrence of Listeria spp., especially L. monocytogenes and its main serotypes, in beef and processing plants. A total of 443 samples were obtained from equipment, installations and products from 11 meat processing establishments from Paraná state, Brazil. All samples were analyzed using USDA methodology for Listeria spp. detection, followed by species identification. The occurrence of Listeria spp. in the samples was 38.1% of which 51.4% were from equipment, 35.4% from installations and 30.2% from products. The identified species were: L. monocytogenes (12.6%), L. innocua (78.4%), L. seeligeri (1.2%), L. welshimeri (7.2%) and L. grayi (0.6%). The identified serotypes of L. monocytogenes were 1/2a and 4b. The results demonstrate the significance of equipment and installations as sources of contamination by Listeria spp. and L. monocytogenes in the processing of beef and meat products.     

Occurrence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella and Campylobacter spp. on beef carcasses in Northern Ireland

A survey of beef carcasses was conducted in all 10 European community approved abattoirs in Northern Ireland to determine the incidence of Escherichia coli O157:H7. Analyses were based on excised samples of neck meat taken less than 48 h post-kill. Overall, 780 carcasses were sampled and all were negative for E. coli O157:H7. A sub-set of samples was analysed for the presence of Listeria monocytogenes (n=200), Salmonella (n=200) and Campylobacter spp.(n=100). L. monocytogenes was not detected but Listeria innocua was found on five carcasses and Listeria seeligeri on one. Three carcasses carried salmonellas; Salmonella Mbandaka was found on two and Salmonella Thompson on one. Campylobacter spp. were not detected on any carcasses. The results indicate that very few beef carcasses in Northern Ireland appear to carry any of the four pathogens sought, and this may help explain the low incidence of E. coli O157:H7 in the Northern Ireland human population, relative to the rest of the UK.     

PFGE characterisation and adhesion ability of Listeria monocytogenes isolates obtained from bovine carcasses and beef processing facilities

Listeria monocytogenes is a pathogen capable of adhering to many surfaces and forming biofilms, which may explain its persistence in food processing environments. This study aimed to genetically characterise L. monocytogenes isolates obtained from bovine carcasses and beef processing facilities and to evaluate their adhesion abilities. DNA from 29 L. monocytogenes isolates was subjected to enzymatic restriction digestion (AscI and ApaI), and two clusters were identified for serotypes 4b and 1/2a, with similarities of 48% and 68%, respectively. The adhesion ability of the isolates was tested considering: inoculum concentration, culture media, carbohydrate source, NaCl concentration, incubation temperature, and pH. Each isolate was tested at 10(8)CFUmL(-1) and classified according to its adhesion ability as weak (8 isolates), moderate (17) or strong (4). The isolates showed higher adhesion capability in non-diluted culture media, media at pH 7.0, incubation at 25°C and 37°C, and media with NaCl at 5% and 7%. No relevant differences were observed for adhesion ability with respect to the carbohydrate source. The results indicated a wide diversity of PFGE profiles of persistent L. monocytogenes isolates, without relation to their adhesion characteristics. Also, it was observed that stressing conditions did not enhance the adhesion profile of the isolates.     

嫩化型牛肉干的研究开发

牛肉干是我国传统的大众食品但其生产一直沿用传统工艺,产品口感坚韧、硬度大,色泽灰白。本研究采用全新的技术,对牛肉进行嫩化、腌 制、熟制和烘干等工艺处理,得到的成品色泽棕红,口感脆嫩,风味良好。     

Antilisterial effects of free fatty acids and monolaurin in beef emulsions and hot dogs

This study was undertaken to screen fatty acids, conjugated isomers of linoleic acid (CLA), and monolaurin for antilisterial effects in broth, and to further test the active compounds in cooked comminuted beef and hot dogs. Capric, lauric, myristic, palmitic, stearic, oleic, linoleic, and linolenic acid, CLA and monolaurin were screened in sterile nutrient broth at concentrations of 5 to 700 μg/ml. The media were inoculated with 10³ cfu/ml of L. monocytogenes strain Scott A and incubated at 32°C for up to 8 days. Cell enumeration data showed that lauric acid was most inhibitory, followed by monolaurin, and capric acid. Tests in comminuted sterile beef stored at 5°C for 21 days showed log cfu/g of: 8.5 (control), 7.3 (500 μg/g lauric acid), and 4.7 (500 lauric acid+300 capric acid). Similar results were observed in beef hot dog emulsion to which lauricidin, lauric acid, capric acid, and the acid combination were added prior to heat treatment. At 500 μg/g, monolaurin and lauric acid caused similar delayed growth effects at 5°C, whereas the combination of the two acids showed enhanced inhibition on prolonged storage. Nonetheless, the observed 5-log increase in numbers of L. monocytogenes during 45 days of storage indicates limited control of the pathogen in refrigerated cooked meat products.     

The effect of family beef taboos on beef consumption on young Taiwanese adults

A family tradition of beef taboos exists in Chinese societies. The marketplace for beef in Taiwan is imported mainly from the U.S., Australia, and New Zealand. For mechanised-farming families or even for those no longer engaged in agriculture, beef consumption is often not encouraged nor allowed by family members. Using quantitative data in the analyses, this study was undertaken to examine whether family beef taboos influenced beef consumption for young adults in Taiwan. Respondents from beef-consuming families consumed more beef (4.34 times/week: average, 150.07 g/week: cooked) than respondents from non-beef-consuming families (1.87 times/week: average, 56.67 g/week: cooked). For the respondents from non-beef-consuming families, spiritual burden was a main factor affecting their own beef consumption. The implications based on this study’s findings are provided.     

Meat quality of young Nellore bulls with low and high residual feed intake

Fifty-nine Nellore bulls from low and high residual feed intake (RFI) levels were studied with the objective of evaluating meat quality traits. Animals were slaughtered when ultrasound-measured backfat thickness reached 4 mm, and samples of Longissimus were collected. A mixed model including RFI as fixed effect and herd and diet as random effects was used, and least square means were compared by t-test. More efficient animals consumed 0.730 kg dry matter/day less than less efficient animals, with similar performance. No significant differences in carcass weight, prime meat cuts proportion, chemical composition, pH, sarcomere length, or color were observed between RFI groups. Shear force, myofibrillar fragmentation index and soluble collagen content were influenced by RFI, with a higher shear force and soluble collagen content and a lower fragmentation index in low RFI animals. Feedlot-finished low RFI young Nellore bulls more efficiently convert feed into meat, presenting carcasses within quality standards.     

Bovine mitochondrial oxygen consumption effects on oxymyoglobin in the presence of lactate as a substrate for respiration

Research suggests that NADH formed from lactate addition can increase mitochondrial oxygen consumption. However, limited research has assessed the subsequent effects of lactate-mediated mitochondrial oxygen consumption on oxymyoglobin. Therefore, our objective was to assess the effects of bovine mitochondrial oxygen consumption on oxymyoglobin in the presence of lactate, LDH, and NAD. Isolated beef cardiac and skeletal muscle mitochondria (n = 5) were reacted with lactate (40 mM), LDH (100 units), and NAD (0.02 mM) to initiate oxygen consumption. Myoglobin redox state was measured to assess the effects of oxygen consumption on oxymyoglobin. The addition of lactate–LDH–NAD to mitochondria increased (p < 0.05) both oxygen consumption and conversion of oxymyoglobin to deoxymyoglobin compared with control mitochondria without substrates. The addition of antimycin A to mitochondria decreased oxygen consumption and deoxymyoglobin formation (p < 0.05). The results suggest that increased oxygen consumption can influence myoglobin redox state and this effect might be partially responsible for the darkening effect in lactate enhanced beef.     

食品中3种致病李氏菌MPCR-DHPLC检测方法的建立

应用复合PCR(multiplex PCR,MPCR)结合变性高效液相色谱(denaturing high-performance liquid chromatography,DHPLC)技术建立食品中单核细胞增生李斯特菌、绵羊李斯特菌和英诺克李斯特菌的快速高通量检测方法。根据单核细胞增生李斯特菌、绵羊李斯特菌和英诺克李斯特菌的特异基因序列分别设计引物,MPCR扩增的产物经DHPLC技术进行快速检测。以94株参考菌株做特异性实验,并开展了重现性检测实验。MPCR-DHPLC方法同步检测到单核细胞增生李斯特菌、绵羊李斯特菌和英诺克李斯特菌的特异性阳性吸收峰,未检测到李斯特菌属其他近源种和非近源种参考菌株的阳性吸收峰,且重现性良好。该方法具有很好的特异性,可以快速、准确、高通量地检测食品中单核细胞增生李斯特菌、绵羊李斯特菌和英诺克李斯特菌,是食品微生物快速检测的新技术。     

基于高分辨率溶解曲线分析鉴别食品中的3种李斯特氏菌

本研究利用高分辨率熔解曲线的方法,以iap基因为靶标新设计一对引物同时鉴别单增李斯特氏菌、伊氏李斯特氏菌和英诺克李斯特氏菌,其余14种常见食源性病原微生物扩增为阴性结果,单增李斯特氏菌和伊氏李斯特氏菌的检出限为10个拷贝,英诺克李斯特氏菌的检测限为50个拷贝。本研究对78份样品进行HRM-realtimePCR法、GB4789.30-2016和SN/T1870-2016(荧光PCR法)的检测,并对3种方法的检测结果进行统计学分析。结果显示:HRM法和国标方法、HRM法和荧光PCR法的检测结果之间存在统计学差异,国标方法和荧光PCR法检测结果之间无统计学差异。本研究建立的基于HRM-real time PCR法检测3种李斯特氏菌的方法快速高效、特异性好、成本低,适用于食品中李斯特氏菌的日常检测和监管。