散装熟肉制品中单增李斯特菌污染状况分析

目的分析散装熟肉制品中单增李斯特菌污染状况。方法根据GB 4789.30-2016《单核细胞增生李斯特氏菌检验》规定的方法对散装熟肉制品的加工用原料、生产环境、各加工环节中产品以及不同销售环境下产品中的单增李斯特菌进行定性和定量检测。结果原料肉的总体带菌率达到21%;生产环境中第三区(远离食品接触面的区域)检出率为2%,其余区域未检出;各加工环节中产品单增李斯特菌检测结果均小于10CFU/g;不同销售环境下产品中单增李斯特菌检测结果小于10 CFU/g的比例为93%,处于10～50 CFU/g之间的样本占比6%,大于50 CFU/g的占比为1%。结论原料散装熟肉制品中单增李斯特菌污染的主要来源,蒸煮等加工环节能有效地杀灭单增李斯特菌。销售环境也关系到散装熟肉制品单增李斯特菌的污染程度,对于未包装的产品,专卖店优于农产品市场。     

Gamma irradiation as a means to eliminate Listeria monocytogenes from frozen chicken meat

Cells of Listeria monocytogenes ATCC 35152 were sensitive to gamma irradiation in phosphate buffer, pH 7.00 (D₁₀, dose required for 10% survival—0.15 kGy) at 0–5°C. The cells showed higher radiation survival when irradiated under frozen condition, with a D₁₀ of 0.3 kGy. The protection offered by shrimp/chicken/kheema homogenates (100 g litre^?1) was evidenced by even higher D₁₀ values (0.5 kGy) at both 0–5°C and cryogenic temperature. Boneless chicken meat samples were artificially inoculated with L monocytogenes ATCC 35152 cells at low (5 × 10³) colony-forming unit (cfu) g^?1 and high (5 × 10⁶ cfu g^?1) concentrations and irradiated at 1, 3, 4, 6 kGy doses under cryogenic conditions. The efficacy of the radiation process was evaluated by detecting L monocytogenes during storage at 2–4°C in the irradiated samples. These studies, when repeated with three other serotypes of L monocytogenes, clearly suggested the need for a dose of 3 kGy for elimination of 10³ cfu cells of L monocytogenes g^?1 from air-packed frozen chicken meat.     

Combined use of bacteriocin‐producing strains to control Listeria monocytogenes regrowth in raw pork meat

Avoiding the presence of Listeria in meat and dairy products is a major challenge for the food industry. In this work, a Lactobacillus curvatus strain producing the bacteriocin sakacin P and a Pediococcus acidilactici strain producing another bacteriocin, pediocin AcH, were used as starter cultures under laboratory conditions in a Listeria‐seeded raw‐pork‐meat matrix, which was then stored for 6 weeks at 4 °C. At 1 week intervals during the storage period, the antilisterial activity was evaluated. When either strain was added alone, the Listeria monocytogenes cfu count initially dropped from 10² cfu g^?1 to an undetectable level by the end of week 1 or 2, but this was followed by a rebound (regrowth) 1 week later. When both strains were added together to the meat matrix, rebound was delayed, Listeria remaining undetected from the end of week 1 to the end of week 5. A rebound was observed 6 weeks post‐inoculation, but fewer than 10 cfu g^?1 were counted. The use of more than one bacteriocin‐producing strain may thus overcome some of the problems limiting the effectiveness of bacteriocins in food systems.     

预包装熟肉制品生产加工过程单核细胞增生李斯特菌污染及病原学特征分析

目的 了解预包装熟肉制品生产加工过程各个环节中单核细胞增生李斯特菌(以下简称单增李斯特菌)污染水平,并分析分离菌株的分子特征及药敏特征,对企业生产质量控制环节提出预防控制措施.方法 2015-2017年在德州市某预包装熟肉制品厂采集生产加工过程中熟肉制品原辅料、中间产品、成品、终产品和环境样品共计460份,依据GB 4...     

肉中单核细胞增生李斯特菌PCR快速检测方法建立

目的:建立单核细胞增生李斯特菌(Listeria monocytogenes,LM)快速、敏感、特异的PCR诊断方法。方法:采用聚合酶链式反应技术(PCR)特异性扩增单核细胞增生李斯特菌内化素基因(ivlA),并评价该方法的特异性与敏感性。结果:在445bp处出现inlA基因的目的片断,只有单增李斯特菌的目的片段获得扩增,其他菌种扩增均呈阴性;该方法可以检测到DNA的检测限。结论:PCR方法比传统细菌检测方法更特异、快速、灵敏和简便;为肉中单增李斯特菌的快速检测提供了新的手段。     

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.     

Effect of Filling Type and Heating Method on Prevalence of Listeria species and Listeria monocytogenes in Dumplings Produced in Poland

The count of Listeria monocytogenes was determined, before and after heat treatment, in 200 samples of dumplings of 9 brands and with different types of stuffing. Analyses were conducted according to ISO 11290–1 standard and with real‐time PCR method. The highest count of L. monocytogenes was found in meat dumplings (10² to 10⁴ CFU/g), whereas products with white cheese‐potato stuffing and vegetable‐mushroom stuffing contained significantly less Listeria, 20 to 80 and 5 to 32 CFU/g, respectively. In cooled meat dumplings the extent of contamination depended significantly on the producer. In addition, a significant (P < 0.05) correlation was determined between contamination level and meat content in the stuffing (rho = 0.418), especially in stuffing containing pork meat (0.464), contrary to beef‐containing stuffing (0.284). Heating dumplings in boiling water for 2 min completely eliminated L. monocytogenes in meat dumplings. In contrast, the microwave heating applied for 2 min at 600 W only reduced the count of L. monocytogenes by 1 to 2 logs. Hence, the microwave heating failed to reduce the risk of infection with this pathogen below the level permissible in the EU regulation, especially in the most contaminated samples. In this case, the efficacy of microwave heating was significantly (P < 0.05) affected by the initial count of L. monocytogenes (rho = 0.626), then by meat content in the stuffing (0.476), and to the lowest extent—by the type of meat (0.415 to 0.425). However, no Listeria sp. and L. monocytogenes were isolated from cooked dumplings with fruits (strawberries or blueberries).     

2010~2016年云南省熟肉制品和餐饮食品中单增李斯特菌污染情况调查分析

目的 了解2010～2016年云南省市售熟肉制品和餐饮食品中单增李斯特菌污染情况调查分析。方法 在全省16个州市县中选取超市、农贸市场、零售及餐饮环节等为采样点, 随机采取熟肉制品1465份和餐饮食品3674份, 按照GB 4789.30-2010《食品安全国家标准 食品微生物学检验 单核细胞增生李斯特氏菌检验》及《全国食源性致病菌监测工作手册》进行检测和鉴定。结果 1465份熟肉制品中单增李斯特菌检出率为2.18%(32/1465), 3674份餐饮食品中单增李斯特菌阳性率为1.44%(53/3674)。在不同流通环节中, 熟肉制品和餐饮制品中检出率最高的分别为便利店和超市, 分别为9.09%(5/55)和1.67%(3/180)。在不同的监测地区, 熟肉制品和餐饮制品检出率最高均为昭通地区, 分别为7.8%(11/141)和7.17%(18/251)。结论 单增李斯特菌在熟肉制品及餐饮食品中均有检出, 说明云南省的食品中存在一定的单增李斯特菌污染, 对消费者的安全有潜在风险, 相关监管部门应持续加强监管, 预防食源性疾病的发生。     

单核细胞增生李斯特菌菌株分型与其致病潜力基因相关性研究进展

单核细胞增生李斯特菌是一种常见的食源性致病菌,该菌分型繁多。不同分型的单核细胞增生李斯特菌致病潜力不同,这与菌株所携带的抗性基因和毒力基因不同有关。本文综述了不同分型单核细胞增生李斯特菌与抗性基因和毒力基因的关系,结果发现与该菌抗性相关的基因,如热抗性、耐冷性、酸抗性、耐高渗、耐干燥、耐金属和杀菌剂及参与应激蛋白表达调控的基因较多,它们与分型之间的关系暂无明确相关性结论,但也发现应激生存岛（stress survival island,SSI）-1仅存在于谱系I和谱系II部分菌株中,SSI-2目前仅被发现在ST121菌株中携带。从功能毒力基因和李斯特菌毒力基因岛（Listeria pathogenicity islands,LIPI）两方面分述了毒力基因,LIPI-3和LIPI-4主要存在于谱系I菌株中。此外,ST5、ST8、ST9和ST121菌株的inlA基因中出现提前终止密码子,使得菌株的毒力降低。研究不同分型单核细胞增生李斯特菌致病潜力基因的差异有助于单核细胞增生李斯特菌的预警预测、防控,并为不同分型菌株致病机制的深入研究提供参考。     

肉及肉制品中单核细胞增生李斯特菌交叉污染的研究进展

单核细胞增生李斯特菌（以下简称单增李斯特菌）是一种引起细菌性食物中毒的重要食源性病原菌,常因污染肉品而引发食物中毒事件,其中交叉污染是引起单增李斯特菌污染并导致食源性疾病的主要途径。本文综述了国内外肉及肉制品污染单增李斯特菌引发的流行病学情况、家庭厨房和肉品加工厂的交叉污染情况、交叉污染模型构建、交叉污染的预防与控制等,为维护家庭食品安全以及保障工厂食品加工卫生安全提供理论依据。     

加工环境中单核细胞增生性李斯特菌耐药特征分析

目的分析在流通过程中加工环境来源的食源性李斯特菌耐药性及耐药基因携带情况,探讨加工环境对该菌的影响。方法收集2016~2017年分离自加工环境中的71株单核细胞增生性李斯特菌,利用微量肉汤稀释法对8种抗菌药物进行药物敏感性分析,并采用PCR鉴定11种耐药基因(tet A、tet M、tet S、erm A、erm B、erm C、mec A、aac(6’)-Ib、van A、van B、cfr)。结果 71株Lm对庆大霉素(11.27%)、氨苄西林(4.22%)、头孢他啶(98.59%)、环丙沙星(97.18%)、四环素(21.12%)、红霉素(15.49%)、林可霉素(92.96%)均具有不同程度的耐药性,对万古霉素敏感。其中以耐受3~6种抗菌药为主,耐药情况较为严重。耐药基因检测表明四环素类tet A,tet M为主要耐药基因,检出率高达50%以上,其次为红霉素类erm A、erm B、erm C,检出率约11%,氨基糖苷类aac(6’)-Ib的检出率为5.63%。结论加工环境单核细胞增生性李斯特菌的耐药性呈上升趋势,其耐药表型与耐药基因型并不完全一致,从而表明加工环境中存在影响单核细胞增生性李斯特菌耐药性因素,同时为食源性李斯特菌病的防治及预警提供参考依据。     

Listeria monocytogenes: Strain Heterogeneity,Methods, and Challenges of Subtyping

Listeria monocytogenes is a food‐borne bacterial pathogen that is associated with 20% to 30% case fatality rate. L. monocytogenes is a genetically heterogeneous species, with a small fraction of strains (serotypes 1/2a, 1/2b, 4b) implicated in human listeriosis. Monitoring and source tracking of L. monocytogenes involve the use of subtyping methods, with the performance of genetic‐based methods found to be superior to phenotypic‐based ones. Various methods have been used to subtype L. monocytogenes isolates, with the pulsed‐field gel electrophoresis (PFGE) being the gold standard. Although PFGE has had a massive impact on food safety through the establishment of the PulseNet, there is no doubt that whole genome sequence (WGS) typing is accurate, has a discriminatory power superior to any known method, and allows genome‐wide differences between strains to be quantified through the comparison of nucleotide sequences. This review focuses on the different techniques that have been used to type L. monocytogenes strains, their performance challenges, and the tremendous impact WGS typing could have on the food safety landscape.     

不同加工条件对茶黄素抑制单增李斯特菌稳定性的影响

目的 探讨不同加工条件对茶黄素(theaflavins, TFs)抑制单增李斯特菌(Listeria monocytogenes, LM)稳定性的影响。方法 以LM为指示菌, 采用二倍稀释法测定了TFs的最小抑菌浓度(minimum inhibitory concentration, MIC), 并在此基础上通过牛津杯法进一步探讨不同加工条件(环境因素: 加工温度、pH、NaCl浓度; 食品基质: 脱脂奶粉、卵磷脂、蔗糖)对TFs抑菌稳定性的影响。结果 TFs对LM的MIC为2 mg/mL, 此时的抑菌效果为中敏水平, LM的正常生长被明显抑制; 加工温度在25~121℃时, TFs对LM的抑菌圈直径无显著性差异; pH在2~10时, 其抑菌圈直径从12.74 mm显著降低至9.86 mm; NaCl摩尔浓度在0.2~0.8 mol/L时, 其抑菌圈直径有所增加; 脱脂奶粉质量浓度在60~120 g/L时, 其抑菌圈直径显著降低; 卵磷脂质量浓度在2~12 g/L和蔗糖质量浓度在10~60 g/L时, 其抑菌圈直径无显著性变化。结论 TFs对LM具有较好的抑菌活性且在不同加工条件下能保持良好的抑菌稳定性。本研究为TFs作为一种新型抗菌产品在食品加工和贮藏中的应用提供了理论依据。     

单增李斯特氏菌MALDI-TOF-MS鉴定与分型研究

为建立单增李斯特氏菌的基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)快速鉴定与分型方法,实验收集37株单增李斯特氏菌分离株,应用MALDI-TOF-MS采集图谱,获取独特的蛋白质指纹图谱,汇总成标准图谱,建立单增李斯特氏菌鉴定数据库。采用单增李斯特氏菌标准菌株进行验证,表明鉴定结果的可信度很高。在数据库信息的基础上,对37株单增李斯特氏菌分离株进行聚类分型。分型结果表明,在蛋白质水平上,MALDI-TOF-MS可把37株单增李斯特氏菌分成9个型别。     

噬菌体对虾仁中单核细胞增生李斯特菌的抑制效果

以虾仁为研究对象,通过人为模拟在虾仁中接种单核细胞增生李斯特菌后,再用噬菌体ListexTMP100在常温(20℃)、冷藏(4℃、0℃)和冷冻(-18℃)环境下进行处理,分析虾仁中该菌的抑制效果,单核细胞增生李斯特菌采用平板计数法进行计数。结果表明:噬菌体浓度大于2×107PFU/mL时,能有效杀灭虾仁中单核细胞增生李斯特菌(P<0.05);该浓度在20℃下作用虾仁1 h,便能降低1.50 Log10CFU/g(死亡率为99%以上)的单核细胞增生李斯特菌;在0℃和4℃,作用24 h下,单核细胞增生李斯特菌的死亡率达到99.9%;在-18℃下贮藏30d,单核细胞增生李斯特菌在第1天下降了1.38Log10CFU/g。这些结果表明,噬菌体ListexTMP100对虾仁中的单核细胞增生李斯特菌具有明显的抑制效果,可作为一种理想的生物杀菌剂用于水产食品中。     

A Simple and Fast PCR Protocol to Detect Listeria monocytogenes from Meat

Primers for the iap gene were used to develop and optimise a PCR technique for detecting Listeria monocytogenes in meat. The use of these primers gave good results in the detection of L monocytogenes in either artificially or naturally contaminated foodstuffs. The lowest sensitivity limit achieved with PCR was 10¹–10² cells ml^-1 or g^-1 product, either in pure cultures or in artificially and naturally contaminated meat. The PCR method devised has high sensitivity and specificity. It appears to give good results and is very easy and fast to perform, requiring only 30 h to detect Listeria from meat, whereas, conventional methods require almost 96–120 h. © 1997 SCI.     

Survival of Listeria monocytogenes, Listeria innocua, and Lactic Acid Bacteria in Chill Brines

ABSTRACT:  Listeria monocytogenes is the pathogen of concern in ready-to-eat (RTE) meat products. Salt brines are used to chill processed meats. L. monocytogenes and lactic acid bacteria (LAB) can grow under saline conditions, and may compete with each other for nutrients. The objective of this study was to determine the effect of lactic acid bacteria ( Enterococcus faecalis , Carnobacterium gallinarum , and Lactobacillus plantarum ) on the survival of L. monocytogenes and Listeria innocua in brines stored under low temperatures for 10 d. Sterile tap water (STW) and 2 brine solutions (7.9% and 13.2% NaCl) were inoculated with 1 of 5 cocktails ( L. monocytogenes , L. innocua , LAB, L. monocytogenes + LAB, or L. innocua + LAB) at initial concentrations of 7 log CFU/mL. Brines were stored for 10 d at 4 or 12 °C. Three replications of each brine concentration/cocktail/temperature combination were completed. No significant reductions of L. monocytogenes occurred in 7.9%[w/v] or 13.2%[w/v] brines when LAB were present; however, there were significant reductions after 10 d of L. monocytogenes in the STW solution when LAB were present (1.43 log CFU/mL at 4 °C and 3.02 log CFU/mL at 12 °C). L. innocua was significantly less resilient to environmental stresses of the brines than L. monocytogenes , both with and without LAB present ( P ≤ 0.05). These strains of lactic acid bacteria are not effective at reducing L. monocytogenes in brines at low temperatures. Furthermore, use of L. innocua as a model for L. monocytogenes is not appropriate under these environmental conditions.     

Characterization of Listeria monocytogenes and Listeria innocua from a vegetable processing plant by RAPD and REA

The incidence of Listeria monocytogenes in a vegetable processing plant was investigated over a 23-month period. Frozen ready-to-eat vegetable samples, well as the plant environment, were sampled. The molecular subtyping techniques, Random Amplified Polymorphic DNA (RAPD) and Restriction Endonuclease Analyses (REA), were performed to help investigate the origin and routes of Listeria dissemination.

The low and sporadic incidence of L. monocytogenes made it impossible to establish an epidemiological sequence in the processing plant, though a case of cross-contamination between tomato and ratatouille was detected. Listeria innocua subtyping, however, allowed us to determine the prevalence of several strains in vegetables, and their presence on machinery samples suggested the possibility of cross-contamination during processing.

The low incidence of L. monocytogenes indicated that the risk of listeriosis transmission by vegetable consumption is low. On the other hand, the isolation of the same strain of L. innocua in several surveys pointed out the risk of colonisation on surfaces and machinery. The persistence of Listeria spp. is a cause for concern as can lead to future contamination of vegetables processed in the plant and to a possible increased risk for health. Therefore, periodic controls for the presence of Listeria spp. and a further review of the cleaning and disinfection procedures used in frozen vegetable plants are recommended.     

Inhibition of Listeria monocytogenes by food antimicrobials applied singly and in combination

Abstract: Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ɛ-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log₁₀ CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FIC_Is) and isobolograms to classify combinations as synergistic (FIC_I < 1.00), additive/indifferent (FIC_I= 1.00), or antagonistic (FIC_I > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ɛ-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ɛ-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces. Practical Application: This study demonstrates the potential for combinations of antimicrobials to result in greater pathogen inhibition as compared to the application of a single antimicrobial. The data presented in this study can aid the food industry in developing more efficient and effective application of antimicrobials. These findings should also prompt further studies validating the inhibitory effect of combinations of antimicrobials on ready-to-eat surfaces.