即食食品中单增李斯特氏菌快速检测技术的研究进展

单核细胞增生李斯特氏菌引发的食品安全事件被广泛关注,它不仅会导致疾病的发生,严重时甚至还会引起感染者死亡,所以即食食品中单增李斯特菌的快速检测技术显得至关重要。本文阐述了不同地区的即食食品中单增李斯特菌的污染率,并综合分析了分子生物学方法、免疫学检测方法、生物传感器检测方法、光谱学检测方法等优缺点以及发展现状,为研发新型快检技术提供新思路。     

食品中单增李斯特菌的检测新技术

单核细胞增生李斯特菌(Listeria monocytogenes,LM)是一种人畜共患食源性致病菌,可使人畜患脑膜炎、心肌炎、败血症、死婴、早产等疾病,危害较大;有效控制食品中的LM,是食品安全的重要课题之一。对以免疫学、分子生物学为基础建立的一些方法,如酶联免疫吸收分析法(ELISA)、酶联荧光分析法(ELFA)、DNA探针、PCR、DNA微矩阵法,作一简单叙述,为深入研究提供参考。最后指出预防手段非常重要,从源头上杜绝LM污染是关键。     

食品中单增李斯特菌快速检测技术研究进展

单核细胞增生性李斯特氏菌(简称单增李斯特菌)是一种广泛存在于自然界中可导致人畜共患病的病原菌, 同时也是一种常见的食源性致病菌。目前, 食品中单增李斯特菌的检测主要采用国标法, 传统检验方法虽然可操作性高, 但检验流程耗时过长。随着生活水平不断提高, 人们在饮食中摄入受单增李斯特菌污染的食品的风险增大, 如遇到食品安全突发事件, 传统检测不能及时得到检测结果, 无法保障人们的饮食安全。本文概述了基于分子生物学和免疫学发展起来的快速检测方法, 包括PCR法、实时荧光定量PCR法、环介导等温扩增法、酶联免疫吸附法、免疫层析试纸条, 其中环介导等温扩增法已经应用于食品致病菌的检测。通过分析对比以上快速检测方法, 为探索更灵敏高效且适用于基层食品检验的检测方法提供参考。     

食品中单核细胞增生李斯特氏菌检测分析

目的:分析食品中单核细胞增生李斯特氏菌的检测结果,以及时发现食品安全隐患,为食品安全监管提供参考依据.方法:严格按照《全国食源性致病菌监测工作手册》中的单核细胞增生李斯特氏菌检验标准,对某市2021年1—12月定期采样的10类常用食品进行单核细胞增生李斯特氏菌检测,分析其阳性检出率.结果:897份10类常用食品中,检出...     

食品中单核细胞增生李斯特菌的危害及其检测

单核细胞增生李斯特菌是一种能引起人畜共患的食源性致病菌之一。近年来 ,在许多国家 ,它被列为卫生部门重点检测的几种食源性致病菌之一。本文综述了单核细胞增生李斯特菌的生理生化特征、分布、污染途径、危害与流行病学概况和检测方法。     

食品中单核细胞增生李斯特氏菌检测结果的分析

目的:分析食品中单核细胞增生李斯特氏菌的检测结果,以及时发现食品安全隐患,为食品安全监管提供参考依据。方法:严格按照《2012年食源性致病菌监测工作手册》中的单核细胞增生李斯特氏菌检验标准,对济宁市2019年1—12月定期采样的8类常用食品(生鲜猪肉、生鲜牛肉、生鲜羊肉、生鲜鸡肉、冻虾、冻带鱼、凉拌菜与冰激凌)进行单核细胞增生李斯特氏菌检测,分析其阳性检出率。结果:567份8类常用食品中,检出单核细胞增生李斯特氏菌27份,阳性检出率为4.76%,其中包括生鲜猪肉6份(5.94%)、生鲜羊肉5份(6.02%)、生鲜鸡肉5份(5.10%)、冻虾4份(7.69%)、冻带鱼2份(3.28%)以及凉拌菜5份(11.63%),生鲜牛肉与冰激凌均未检出单核细胞增生李斯特氏菌。结论:食品中存在单核细胞增生李斯特氏菌污染的风险,其中以凉拌菜的污染风险最高,应加强该方面的防控,以确保食品安全。     

江干区部分食品中单增李斯特菌污染状况分析

目的了解江干区食品中单核细胞增生性李斯特菌污染状况。方法参考国标方法,采用进口显色培养基,对4类食品进行单核细胞增生性李斯特菌分离,生化及血清型鉴定。结果109份样品共检出单核细胞增生性李斯特菌15株,总检出率为13.8%;生肉类、生食果蔬类检出率分别为36.8%、5.9%,熟肉制品和水产品中未检出。15株单核细胞增生性李斯特菌分属2个血清型,1/2b血清型占73.3%,1/2a血清型占26.7%。结论江干区食品中存在单核细胞增生性李斯特菌的污染,特别是生肉。     

食品中单增李斯特菌检测进展

研究表明,单增李斯特菌能使人和牲畜共同患病,治病感染性极强,并且已成为四大食源性疾病致病菌之一,因此,对于食品中单增李斯特菌的检测尤为重要.主要介绍国标法和快速检测单增李斯特菌的方法,对我国食品安全问题的管理工作以及保障社会的稳定具有十分重要的意义,并且对国内外不同检测单增李斯特菌的方法做出了整体的比较,对比其检出限与...     

用PCR技术快速检测食品中的单核细胞增生性李斯特菌

建立了食品中单核细胞增生性李斯特菌快速、敏感、特异的聚合酶链反应PCR检测方法.选择的引物具有良好的单增李氏菌种的特异性.对人工污染在冷冻食品中单增李氏菌的检测低限是4-8CFU/10g,对其增菌液的检测低限是7.2-11×103/ml,每PCR反应体系的检测低限为86-132CFU.对400份自然污染样品的检测结果显示,PCR方法的检测结果同常规培养法的结果完全相符.     

RapidChek检测食品中单增李斯特菌的方法评价

目的评价RapidChek法检测食品中单增李斯特菌的检测效果并验证。方法采用t检验,比较RapidChek方法与GB 4789.30-2016方法的培养基增菌效果。依据ISO 16140:2003《食品和动物饲料微生物学-可替代方法的验证方案》,比较RapidChek检测方法与GB 4789.30-2016检测方法的检测效果,涉及的性能指标有相对准确性、相对特异性和相对灵敏度、包含性和排他性。结果 RapidChek检测方法增菌培养基效果优于GB 4789.30-2016方法增菌培养基LB_1。根据RapidChek检测方法、GB 4789.30-2016培养基+RapidChek试纸条方法、RapidChek培养基+GB 4789.30分离鉴定方法的统计检验得出,3种方法与参照方法在相对准确性、相对特异性和相对灵敏度方面无显著性差异。在包含性和排他性方面,RapidChek检测方法与GB 4789.30-2016检测方法的检测结果均一致。结论在所验证的指标上,RapidChek检测方法(包括与GB4789.30-2016组合的方法)与GB 4789.30-2016方法无差异。     

INFLUENCE OF FOOD ENVIRONMENT ON LISTERIA MONOCYTOGENES INFECTION IN THE GUINEA PIG MODEL

Listeria monocytogenes is a widespread foodborne pathogen associated with severe illness in humans. Food composition, processing, storage, distribution and handling conditions are all factors that may individually or collectively contribute to the virulence of a pathogen. Using the guinea pig as a human surrogate, we investigated the impact of carrier vehicle and improper food handling practices on the infectivity of L. monocytogenes. Chocolate milk was artificially contaminated with L. monocytogenes prior to exposure to improper handling conditions. Improper handling of chocolate milk included leaving the milk at an elevated temperature (37C) and then placing it in a refrigerator (4C). Guinea pigs were orally challenged with either 10² or 10⁸ cfu of L. monocytogenes in 1 mL of nutrient broth or chocolate milk that had been exposed to improper handling conditions. A third group was challenged with L. monocytogenes suspended in water. On days 2 and 4, upon enrichment of organ samples, the presence of L. monocytogenes was detected in 27% of the animals receiving the low dose regardless of the carrier vehicle and improper handling conditions. Animals fed the high dose (10⁸ cfu) of L. monocytogenes had similar populations of the pathogen in the spleen and liver, regardless of the carrier vehicle. These results are significant in that a low dose (10² cfu) could lead to listerial infection. Under the conditions tested in this study, the carrier vehicle and exposure of the pathogen to improper handling practices had no detectable effect on the establishment of listerial infection in the guinea pig model.     

EXPOSURE OF LISTERIA MONOCYTOGENES TO FOOD AND TEMPERATURE ABUSE USING A DIALYSIS TUBING CULTURE METHOD

Foodborne illnesses are often linked to foods that have been contaminated postprocessing and exposed to temperature abuse conditions prior to consumption. Limitations in methods to recover sufficient numbers of a target bacterium from an (inoculated) intentionally contaminated food can hinder genomic/proteomic analysis, and in conducting in vitro assays using the recovered cells. In this study, a dialysis tubing culture technique was developed to facilitate the recovery of high numbers of Listeria monocytogenes exposed to temperature abuse while in association with chocolate milk and frankfurter slurry. The impact of exposure to foods, followed by temperature abuse, on the virulence of L. monocytogenes was investigated using the Caco‐2 cell infection assay. The expression of groEL, associated with stress, was also determined. L. monocytogenes inoculated into brain–heart infusion (BHI) broth (control), chocolate milk or frankfurter slurry was held at 4C for 24 h to simulate short‐term exposure to each food. The L. monocytogenes‐contaminated food was then exposed to a series of temperature shifts to simulate temperature abuse. The final temperature of the abused BHI and chocolate milk was 30C, and the frankfurter slurry was 22C. The stress response gene, groEL, was only induced in the control cells (suspended in BHI) after they had been exposed to temperature abuse conditions. The expression of groEL was also evident in cells exposed to foods and temperature abuse conditions, suggesting that the foods used in this study were a stressful environment for the cells. This study showed that the exposure of L. monocytogenes to chocolate milk or frankfurter slurry, or temperature abuse has no impact on the virulence of L. monocytogenes as demonstrated using the Caco‐2 cell assay. However, the expression of groEL suggests that the foods evaluated can be stressful environments for L. monocytogenes despite its ability to grow or survive in those foods. The dialysis tubing culture technique developed is a simple and highly cost‐effective method for exposure of bacteria to food and the recovery of a large number of cells suitable for additional analysis.     

人工模拟抗体在食品快速检测中的应斥及目前存在的问题

人工模拟抗体通过对天然的抗体以仿生学的模仿而人工合成的对目标分子具有特异性的分子识别能力的元件。人工模拟抗体是通过功能单体和交联荆对模板分子进行分子印迹而制备得到。因而，人工模拟抗体也叫分子印迹聚合体。由于分子印迹聚合体的活性的稳定性和低廉的价格，因此，在食品的快速检测上得到了应用，如兽药残留、农药残留、微生物的快速检测。但是，由于它一种新型的分子识别材料，存在的一些问题，如对大分子物质的识别不稳定等，还有待于进一步的改善。     

人工模拟抗体在食品快速检测中的应用及目前存在的问题

人工模拟抗体通过对天然的抗体以仿生学的模仿而人工合成的对目标分子具有特异性的分子识别能力的元件.人工模拟抗体是通过功能单体和交联剂对模板分子进行分子印迹而制备得到.因而,人工模拟抗体也叫分子印迹聚合体.由于分子印迹聚合体的活性的稳定性和低廉的价格,因此,在食品的快速检测上得到了应用,如兽药残留、农药残留、微生物的快速检测.但是,由于它一种新型的分子识别材料,存在的一些问题,如对大分子物质的识别不稳定等,还有待于进一步的改善.     

COMPETITION OF FOOD BACTERIA WITH LISTERIA MONOCYTOGENES DURING ENRICHMENT CULTURE

Thirty-two foodborne bacterial isolates were tested as potential competitors of Listeria monocytogenes strain LM82 during enrichment because of their resistance to the selective agents in Listeria enrichment and isolation media. Competitive ability of each isolate was classified as weak, moderate, or strong by determining the ratio at which it masked identification of LM82 at an inoculation concentration of 10 colony forming units (CFU)/10 mL of Listeria enrichment broth. Of the competitive isolates identified, six were Enterococcus spp., two were Staphylococcus spp., and one was a Corynebacterium sp. Although several strains of Enterococcus faecium were examined, not all were competitive. Of six other bacterial strains associated with food fermentations and tested for competitiveness with LM82, one, a Gram-positive tetrad, was competitive. This study showed that although food microfloral strains that are able to survive in enrichment and isolation environments are fairly common, they do not necessarily compete with Listeria. Not all strains in a competitive species are necessarily competitive .     

DISTRIBUTION PACKAGING METHOD AND STORAGE TIME EFFECTS ON THE MICROBIOLOGICAL CHARACTERISTICS AND INCIDENCE OF THE PATHOGENS LISTERIA MONOCYTOGENES AND SALMONELLA IN PORK1

Microbiological and yield characteristics were determined on bone-in pork loins and Boston butts (n = 65 each) that were selected from a commercial facility and subjected to one of three packaging treatments: (1) paper wrapped, (2) modified atmosphere packaging (66% O, 2.26% CO₂ and 8% N₂), and (3) vacuum packaging. Cuts were stored up to 21 days at 0 ± 2C for yield characteristics and an added 28 and 35 days for microbiological characteristics. Treatment and storage effects on the incidence of the pathogens Listeria monocytogenes, Salmonella and numbers of aerobic bacteria, lactic acid bacteria and coliforms were determined. The amount of purge was variable (100 to 500 g) among packaging treatments. The vacuum packaged and modified atmosphere packed pork loins and butts had lower aerobic plate counts (P < .05) compared with the paper wrapped loins and butts. The numbers of Listeria species decreased at a greater rate for the vacuum packaged and modified atmospheric packaged pork loins compared with the paper wrapped loins. No Salmonella were found on meat from any packaging treatment or storage time. The microbial quality of pork loins and butts can be improved by using vacuum packaging compared with paper wrapping or modified atmosphere packaging.     

BACTERIOCIN EXPOSURE AND FOOD INGREDIENTS INFLUENCE ON GROWTH AND VIRULENCE OF LISTERIA MONOCYTOGENES IN A MODEL MEAT GRAVY SYSTEM

The antilisterial activity of bacteriocin-producing Lactobacillus sakei 1 bac⁺ alone and combined with food ingredients (sodium chloride, D-glucose, oregano, black pepper) was studied in a model meat gravy (1.8% proteose peptone, 1.2% meat extract, 0.6% yeast extract, 2.0% corn starch) kept under refrigeration for 10 days. Two strains of L. monocytogenes (serotypes 4b and 1/2a) were employed in coinoculation experiments and Lactobacillus sakei ATCC 15521 was used as a negative control for bacteriocin production. The LAB bac⁺ strain was more effective in inhibiting both L. monocytogenes serotypes than the LAB bac⁻ strain. The serotype 4b was more sensitive to bacteriocin than serotype 1/2a. The effect of the ingredients on inhibition of L. monocytogenes was serotype dependent. Bacteriocin exposure did not affect sensitivity to ampicilin and rifampicin. However, L. monocytogenes partially lost their hemolytic activity after exposure to bacteriocin-producing Lb. sakei 1 and food ingredients.     

THE INCIDENCE AND LEVEL OF LISTERIA SPP. AND LISTERIA MONOCYTOGENES CONTAMINATION IN PROCESSED POULTRY AT A POULTRY PROCESSING PLANT

To estimate the incidence and levels of Listeria spp. in an industrial poultry processing plant, samples of chicken breast meat, livers, surfaces of saws and tables, hands and gloves were analyzed. Forty percent of the breast samples presented Listeria: L. monocytogenes, L. innocua and L. grayi. Liver samples were contaminated by L. innocua and L. grayi. High levels of Listeria monocytogenes were found on saws (<30–2400 MPN/equipment) and tables (<30–11,000 MPN/equipment). Hands were contaminated by L. monocytogenes, L. innocua and L. grayi and gloves with L. innocua and L. grayi. The levels of Listeria on hands and gloves were low (<110 MPN/hand). L. monocytogenes serotypes were 1/2a, 1/2b, 1/2c and 4b. Overall, the study demonstrated the high prevalence of Listeria spp. and specifically L. monocytogenes in chicken breast meat, equipment and hands. Improvements and innovations at the poultry processing plant may effectively reduce final production contamination with Listeria.     

INFLUENCE OF FAT CONTENT AND PRESERVATIVES ON THE BEHAVIOR OF LISTERIA MONOCYTOGENES IN BEAKER SAUSAGE

Behavior of Listeria monocytogenes Scott A in pork liver sausage containing 22–67% fat, and antilisterial activities of sodium lactate, sorbic acid, potassium sorbate and sodium propionate were studied during storage at 4C and 10C. Commercial pork liver sausage batter (22% fat), alone and with additions of lard (15, 30, and 45% by weight) were tested. Concentrations of 1.8% sodium lactate, 0.1% sorbate as the acid or the potassium salt, and 0.2% sodium propionate were tested in heat sterilized sausage inoculated with a 24 h culture of the organism (10⁴ CFU/g). Fat content alone caused small reductions in cell numbers by the end of the storage periods: from log CFU/g of 9.9 to 9.4 after 14 days at 10C, and from 7.3 to 6.5 after 50 days at 4C in the basic sausage formulation and with 45% added fat, respectively. The inhibitory activities of lactate and propionate increased with increase in fat content, and were more pronounced at 4C, where the effects were listericidal. Inhibition by sorbic acid was least influenced by the fat content, and the potassium salt was less antilisterial than the acid.