环境因子交互作用下蜡样芽孢杆菌生长/非生长界面模型的建立与评价

本文旨在建立一种生长/非生长界面模型来预测蜡样芽胞杆菌在环境因子交互作用下的生长概率。选取五株蜡样芽孢杆菌菌株的混合菌株作为研究对象,研究温度、pH、Aw对混合菌株生长概率的交互影响。获得的生长/非生长实验数据用logistic回归方程拟合,建立了环境因子交互作用下蜡样芽孢杆菌生长/非生长界面模型。实验采取部分析因设计方案,选定80%的实验数据用做模型的拟合,20%的数据用做模型的验证。并从已发表的文献中选取30个数据作为测试集,通过比较预测值和观察值来检测已建模型的适用度。实验结果表明,训练集的一致性指数为0.991,验证集的一致率为0.988,说明模型对同类数据预测准确度高;同时模型的R2-Nagelkerke值也较高,为0.949;Hosmer-Lemeshow检验中的χ2=0.012,P=1,logistic回归模型拟合度较高。模型对测试集的预测准确率达83.3%,该模型对所选数据具有较高的预测能力,说明模型具有较广的适用范围。     

软烤贻贝中蜡样芽孢杆菌生长/非生长界面模型建立与评价

建立软烤贻贝中蜡样芽孢杆菌标准菌株(ATCC49064与DSMZ 4312)在不同贮藏温度(T)、pH、水分活度(Aw)下生长/非生长界面模型,对其拟合情况和来自软烤贻贝蜡样芽孢杆菌(YB001)的验证情况进行分析和评价,并与已建立的脑心浸出液肉汤(BHI)中蜡样芽孢杆菌生长/非生长界面模型进行比较。所建模型总方程为Lopit(P)=-208.457-2.167·T+35.304·pH+705.573·Bw+1.117·T·pH-7.072·T·Bw-174.946·pH·Bw,其中R2-Nagelkerke=0.979和χ~2=0.019(df=8,P=1)显示拟合度较高,而且其预测一致率明显高于BHI培养基中建立的模型,表明该模型在预测软烤贻贝中蜡样芽孢杆菌的生长/非生长情况有很高的精确度和很好的适用性。此外,贮藏温度、水分活度、pH及其交互作用显著影响蜡样芽孢杆菌的生长/非生长(P0.05)。因此可以通过所建生长/非生长界面模型量化温度、水分活度、pH值等栅栏因子并结合其交互效应来确保软烤贻贝的高品质与安全性。     

蜡样芽胞杆菌生长特性及大蒜精油对其抑菌活性的研究

主要研究了37℃条件下3种蜡样芽胞杆菌在营养肉汤中的生长状况,建立了37℃下蜡样芽胞杆菌在营养肉汤中的Boltzmann牛长模犁,3条牛长曲线相关系数鼯均大于0．97;检测了不同培养时间蜡样芽胞杆菌的产芽胞情况,结果表明1号菌株和14号菌株较早产芽胞,培养相同时间,产芽胞数：1号菌株,4号菌株〉标准菌株;采用牛沣杯法和平板计数法研究了大蒜精油对蜡样芽胞杆菌的抑制效果,结果表明浓度为lO。的人蒜精油对3种蜡样芽胞杆菌都有很好的抑制效果,3种菌株中l号菌株最难抑制。     

蜡样芽胞杆菌食物中毒死亡案例分析

一般由蜡样芽胞杆菌(Bc)引起的食物中毒通常症状较温和而且可自愈.但随着国内外相关研究的深入,发现少数Bc食物中毒可能导致非常严重的后果,甚至致死.本研究主要分析国内外已报道的Bc食物中毒死亡案例12起,探讨其中的规律和共性.     

乳酸对蜡样芽胞杆菌的抑制研究

本文研究了乳酸在营养肉汤培养基对蜡样芽胞杆菌的抑制,以及前期乳酸浸泡大豆后对蜡样芽胞杆菌在天培中生长情况的影响.研究发观,在营养肉汤培养基中,当采用乳酸调整pH时,在pH值为4.5时可以较好地抑制蜡样芽孢杆菌的生长.在天培的制作过程中,在前期未加乳酸浸泡处理的天培中,菌数可达108cfu/g并最终导致天培的酸败;在前期加乳酸浸泡处理过的天培中,蜡样芽胞杆菌亦可以生长,但菌数有所下降,为106cfu/g,乳酸浸泡对抑制天培中蜡样芽胞杆菌的生长起到一定的作用.     

一株蜡样芽胞杆菌的鉴定及鉴别诊断

我室接收蜡样芽胞杆菌菌种一株,经我室鉴定为蜡样芽胞杆菌７型,现报告如下。     

广州市市售食品中蜡样芽胞杆菌监测结果分析

目的 了解广州市市售食品中蜡样芽胞杆菌污染及分布情况, 发现危险因素。方法 2014~2018年共采集6类共2011份食品样品, 开展蜡样芽胞杆菌监测分析。结果 蜡样芽胞杆菌检出阳性样品共146份, 总体检出率为7.26%。其中6份样品蜡样芽胞杆菌检出值超过105 CFU/g。不同食品类别中小摊贩食品检出率最高, 达到了10.62%, 其次为烘焙食品(8.69%)、寿司(7.50%)、冷藏膳食(6.67%)、盒饭(6.36%)和熟制米面制品(5.00%)。第3季度检出率最高, 为8.77%, 其次为第2季度(7.98%), 最低的是第1季度(5.09%)。不同采样场所中采自小摊贩的食品蜡样芽胞杆菌检出率最高(11.21%), 其次为餐饮单位(9.31%)和农贸肉菜市场(8.07%), 最低的是超市(6.56%)。散装食品蜡样芽胞杆菌检出率(7.61%)高于预包装食品(5.38%)。中心城区食品蜡样芽胞杆菌检出率(9.24%)高于周边区(3.65%)。结论 广州市市售食品存在不同程度的蜡样芽胞杆菌污染, 部分食品存在安全隐患, 相关部门应针对性加强监管, 预防食源性疾病的发生。     

北京地区饲料添加剂中蜡样芽胞杆菌的检测及分析

目的分析北京地区饲用酶制剂、微生态制剂和混合型饲料添加剂产品中蜡样芽胞杆菌污染情况。方法本实验方法在GB/T26427-2010《饲料中蜡样芽胞杆菌的检测》基础上进行优化,利用VITEKII Compact 15全自动生化鉴定及药敏分析系统,对生产环节的94批次样品,进行计数检测和生化鉴定分析。结果对94批次样品进行检测分析,46批次检出蜡样芽胞杆菌,检出率为48.94%。其中30批次样品含量102CFU/g,占总样品数31.91%;4.26%的样品中蜡样芽胞杆菌含量103CFU/g,分别为饲料添加剂植酸酶2批次,混合型饲料添加剂复合酶制剂2批次。结论北京地区饲用酶制剂、微生态制剂和混合型饲料添加剂产品,存在不同程度上被蜡样芽胞杆菌污染的情况。其中酶制剂类产品的污染状况最为严重,酶制剂和含有酶制剂成分的混合型饲料添加剂产品中蜡样芽孢杆菌检出率均高于50%。     

一株米源蜡样芽胞杆菌的分离鉴定及米饭中生长模型的构建

本文从市售大米中分离筛选出一株蜡样芽胞杆菌,对其进行形态学观察、生理生化鉴定、基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)鉴定、gyrB基因和毒力基因PCR鉴定。分别在4、10、20、25、30 ℃和35 ℃温度条件下,对该菌分别采用修正Gompertz方程、Ratkowsky方程建立初级生长模型和次级生长模型,并对其产毒时间和产毒菌落数的相关性进行研究。结果标明,该蜡样芽胞杆菌携带腹泻型毒力基因(hblA、hblC、hblD、nheA、nheB、nheC、cytK、bceT、entFM),未被检测出呕吐型毒力基因(ces、NRPS)。10 ℃ ~ 35 ℃范围内,随着温度的上升,YLM-3达到稳定期的时间越短,均达到产肠毒素的菌落数阈值(5.5 ~ 6.0 lg(CFU·g-1));4 ℃下,其菌落数维持在1.5 lg(CFU·g-1)左右。该蜡样芽胞杆菌在10 ℃ ~ 35 ℃范围内的生长模型构建良好,可用于预测米饭中蜡样芽胞杆菌的生长。     

Model for Combined Effects of Temperature, pH and Water Activity on Thermal Inactivation of Bacillus cereus Spores

Initially, the effect of water activity (a_w) on heat resistance of Bacillus cereus spores (decimal reduction time) was investigated. A linear relationship was found between log D and 1-a_w. The combined effects of temperature (85-105°C), pH (4.5-6.5) and water activity (0.80-1) were then studied. A four parameter model was fitted to the data. This model appeared to be parsimonious with each parameter having a biological significance. Interactions between factors were observed but they accounted for <2.4% of the total variation and they were not taken into account by the model.     

培养条件对蜡样芽孢杆菌生物被膜生长的影响

以常见的食源性致病菌蜡样芽孢杆菌为研究对象,采用超声平板计数法对其生物被膜形成过程中的不同影响因素进行了研究。结果表明:在37℃、富营养环境、中性及弱碱性条件下,蜡样芽孢杆菌易形成大量生物被膜;添加低浓度的NaCl和葡萄糖均可促进生物被膜的形成,但促进作用不明显;添加高浓度的NaCl和葡萄糖对蜡样芽孢杆菌生物被膜生长有显著抑制作用。     

Growth/no growth interfaces of Bacillus cereus, Staphylococcus aureus and Salmonella enteritidis in model systems based on water activity, pH, temperature and ethanol concentration

This study focuses its attention on the boundary between the growth and no growth of three strains ofSalmonella enteritidis , Bacillus cereus and Staphylococcus aureus in the presence of growth controlling factors such as temperature, pH, water activity (A_w) and ethanol concentration. Preliminarly, the minimal values of pH, A_wand temperature, and the maximum ethanol concentrations allowing the growth of the considered micro-organisms were determined. The calculation of these values enabled the use of logistic model to evaluate the growth/no growth boundary for the bacteria in relation to the considered independent variables. The location of the growth/no-growth boundaries for S. enteritidis and Staph. aureus were strongly affected, at the same ethanol concentration, by temperature, pH and A_w. Among the considered species, Staph. aureus was endowed with the highest sensitivity to low pH values whileB. cereus's growth/no growth interface, was quite unaffected by the combination of the stresses, when the physico–chemical conditions were above the minimum for growth. The effects of temperature, A_wand ethanol on the limitation of growth of the considered species were not merely additive. It was possible to identify the combinations of such factors preventing the growth of Salmonella enteritidis, Staph. aureus and B. cereus.     

Development of a multi-classification neural network model to determine the microbial growth/no growth interface

Boundary models have been recognized as useful tools to predict the ability of microorganisms to grow at limiting conditions. However, at these conditions, microbial behaviour can vary, being difficult to distinguish between growth or no growth. In this paper, the data from the study of Valero et al. [Valero, A., Pérez-Rodríguez, F., Carrasco, E., Fuentes-Alventosa, J.M., García-Gimeno, R.M., Zurera, G., 2009. Modelling the growth boundaries of Staphylococcus aureus: Effect of temperature, pH and water activity. International Journal of Food Microbiology 133 (1-2), 186-194] belonging to growth/no growth conditions of Staphylococcus aureus against temperature, pH and a_w were divided into three categorical classes: growth (G), growth transition (GT) and no growth (NG). Subsequently, they were modelled by using a Radial Basis Function Neural Network (RBFNN) in order to create a multi-classification model that was able to predict the probability of belonging at one of the three mentioned classes. The model was developed through an over sampling procedure using a memetic algorithm (MA) in order to balance in part the size of the classes and to improve the accuracy of the classifier. The multi-classification model, named Smote Memetic Radial Basis Function (SMRBF) provided a quite good adjustment to data observed, being able to correctly classify the 86.30% of training data and the 82.26% of generalization data for the three observed classes in the best model. Besides, the high number of replicates per condition tested (n = 30) produced a smooth transition between growth and no growth. At the most stringent conditions, the probability of belonging to class GT was higher, thus justifying the inclusion of the class in the new model. The SMRBF model presented in this study can be used to better define microbial growth/no growth interface and the variability associated to these conditions so as to apply this knowledge to a food safety in a decision-making process.     

微波对小麦粉中蜡样芽孢杆菌的杀菌效果

该文以灭菌率及生长趋势为评价指标,研究了样品水分含量、微波功率、处理时间对蜡样芽孢杆菌灭菌效果的影响,并通过正交试验探索了微波处理对小麦粉中蜡样芽孢杆菌的最优灭菌条件。结果表明,随样品水分含量升高微波处理对蜡样芽孢杆菌的杀灭率呈现先升高后降低的趋势,且在样品水分含量为15%时,杀灭率最高;微波对蜡样芽孢杆菌的杀灭率随处理时间和微波功率的增加而提高,当微波功率达到581 W时,能够将小麦粉中蜡样芽孢杆菌含量降低到103CFU/g。正交试验结果表明,在处理时间7.5 min,微波功率700 W,样品水分含量15%的条件下,微波处理对蜡样芽孢杆菌的灭菌效果最佳,杀灭率可高达99%。     

食品中蜡样芽孢污染特点及检测方法研究进展

蜡样芽孢杆菌引发的食物污染大都是和人们生活息息相关的食品,在特定条件下对人们的身体健康会带来很大危害.文章综述了粮食制品、含乳制品、豆制品及其他易污染食品中蜡样芽胞杆菌的污染特点,并总结了国内外学者最新研究的检测蜡样芽胞的手段,为全面了解蜡样芽孢杆菌污染状况以供制定相关食品限量标准、完善检测方法提供参考.     

A simplified approach for modelling the bacterial growth/no growth boundary

A simplified growth/no growth (G/NG) model, conceptually derived from the Gamma model and making direct and explicit use of growth limits of bacteria through a normalization constant (η), was proposed. The η value, which quantifies the product of the cardinal optimal distances for growth probability, is a species-independent constant. This is of importance when experimental data is missing or insufficient. The simplified G/NG model was developed including the effect of temperature, pH and water activity, and was expanded incorporating the preservative effects. As a practical application, the model was investigated for its ability to describe published data. The successful validation of the simplified G/NG model is discussed in regard to its potential applicability as a first estimate method for the development of safe food products.     

Influence of pH and temperature on growth of Bacillus cereus in vegetable substrates

Bacillus cereus is a food-borne pathogen which most often contaminates foods of plant origin. Spores of psychrotrophic strains have the ability to germinate and grow at refrigeration temperatures in different vegetable substrates, such as carrot broth, zucchini broth, and cooked carrot purée. In some circumstances, factors such as pH, heat treatment, and storage temperature play a fundamental role in controlling the growth of these psychrotrophic strains and in extending the shelf life of refrigerated, minimally processed vegetable-based products in relation to pathogenic spore-forming bacteria. The combination of mild acidification (pH 5.0) and refrigeration (相似文献