茶多酚、柠檬醛和肉桂醛对食源菌生物被膜的影响研究

研究茶多酚、柠檬醛、肉桂醛在亚抑菌浓度下对食源性金黄色葡萄球菌和肠炎沙门氏菌生物被膜形成能力的影响.采用二倍稀释法确定三种物质的最小抑菌浓度,在亚抑菌浓度下作用于10株金黄色葡萄球菌和10株肠炎沙门氏菌,用微孔板法检测两种细菌生物被膜形成情况.结果表明茶多酚、柠檬醛、肉桂醛在亚抑菌浓度下对金黄色葡萄球菌和肠炎沙门氏菌均有不同程度的抑制作用,差异有统计学意义(P＜0.05),且随着各物质浓度的加大抑制作用也增强,茶多酚对革兰氏阳性菌金黄色葡萄球菌成膜抑制能力比对革兰氏阴性菌肠炎沙门氏菌的成膜抑制能力要强,差异有统计学意义(P＜0.05).柠檬醛和肉桂醛对两种不同细菌的成膜抑制能力没有差异.     

具有抑菌特性的乳杆菌对食源性病原菌生物被膜形成的影响

以金黄色葡萄球菌、大肠杆菌和沙门氏菌为指示菌,研究分离自内蒙古传统发酵食品中的5株乳杆菌对病原菌及其生物被膜的抑制作用。结果表明,5株乳杆菌对单一菌和混合菌生物被膜及AI-2分子相对活性均有抑制作用;ALAC-1和ALAC-5代谢产物抑菌效果较好,尤其对金黄色葡萄球菌抑制作用最好,ALAC-5抑菌率高达78.95%,ALAC-1可达69.47%;混合菌生物被膜对5株乳杆菌代谢产物的敏感性较弱,乳杆菌对其生物被膜抑制作用明显低于单一菌生物被膜。     

腐败牛奶中三种细菌生物被膜特性探究

生物被膜的形成给牛奶保藏和保鲜带来极大的隐患,探讨牛奶腐败过程中生物被膜形成特性以及寻求有效的抑制生物被膜的方法具有重要意义。本实验通过微孔板法模拟牛奶腐败过程,研究食源性金黄色葡萄球菌、肠炎沙门氏菌和大肠杆菌在牛奶中生物被膜形成能力、生物被膜中活菌数目与种间群体感应信号分AI-2活力三者之间的关系。随后利用AI-2抑制剂呋喃酮,检测三种细菌生物被膜形成能力及AI-2活力变化。最后证明,三种细菌生物被膜形成能力、生物被膜中活菌数目以及AI-2活力顺序均是金黄色葡萄球菌大肠杆菌沙门氏菌。添加呋喃酮之后,三种细菌的生物被膜形成能力以及AI-2活力均下降,其中金黄色葡萄球菌的生物被膜形成能力下降为原来的25%。因此表明,此三种细菌生物被膜形成能力的大小可能是是通过调节生物被膜中AI-2的活力实现的。     

右旋龙脑和肉桂醛抑制游离态和生物被膜态食源致病菌的研究

目的:以天然产物右旋龙脑和肉桂醛为研究对象,研究其抑制游离态和生物被膜态单核增生李斯特菌和鼠伤寒沙门氏菌的特征。方法:在采用微量肉汤稀释法研究右旋龙脑和肉桂醛单独对游离态单核增生李斯特菌、鼠伤寒沙门氏菌及其混合菌的最低抑菌浓度(MIPC)的前提下,分析两种天然产物共同作用下对游离态致病菌的最低抑菌浓度以及对生物被膜态致病菌的最低抑菌浓度(MIBC)。结果:右旋龙脑对游离态单核增生李斯特菌的MIPC为0.56 mg/mL,对游离态鼠伤寒沙门氏菌的MIPC为0.58 mg/mL,对混合菌的MIPC为0.60 mg/mL;添加肉桂醛时的3种培养状态下MIPC均为0.40μL/mL;在右旋龙脑和肉桂醛共同作用下(即0.50 mg/mL右旋龙脑和0.40μL/mL肉桂醛)对游离态菌体均可完全抑制,而2.50 mg/mL右旋龙脑和2.00μL/mL肉桂醛共同作用下可以完全抑制生物被膜态的菌体。结论:两种天然产物对生物被膜态菌体的最低抑菌浓度远远大于游离态菌体,右旋龙脑和肉桂醛在抑制游离态菌体和生物被膜态菌体生长方面具有协同作用。     

茶多酚对肉源腐败菌和致病菌的抑制效果

研究了茶多酚对肉源荧光假单胞菌、鼠伤寒沙门氏菌、大肠杆菌、金黄色葡萄球菌的抑制效果。设计不同浓度茶多酚溶液(0.0%、0.5%、1.0%、2.0%、2.5%),采用滤纸片法评判抑制效果。结果表明,茶多酚溶液(0.5%、1.0%、2.0%、2.5%)对荧光假单胞菌有极显著的抑制效果(P<0.01),常用的防腐剂山梨酸钾(1.0%)对其抑制效果却不显著(P>0.05)。茶多酚溶液(1.0%、2.0%、2.5%)和山梨酸钾溶液(1.0%)对鼠伤寒沙门氏菌、大肠杆菌、金黄色葡萄球菌有极显著的抑制效果(P<0.01),茶多酚溶液(0.5%)对鼠伤寒沙门氏菌、大肠杆菌、金黄色葡萄球菌无显著的抑制效果(P>0.05)。通过茶多酚溶液的浓度与4种菌抑菌圈直径的直线相关图可以看出,茶多酚溶液的浓度与鼠伤寒沙门氏菌抑菌圈直径的相关系数最大,荧光假单胞菌次之,其次是金黄色葡萄球菌、大肠杆菌。     

茶多酚及其金属离子对肉源腐败菌和致病菌抑制效果的研究

研究了茶多酚、p H及其金属离子(K+、SO42、Ba2+、Cl-、Mn2+、Cu2+、Na+和Fe3+)对肉源荧光假单胞菌、沙门氏菌、大肠杆菌、金黄色葡萄球菌和枯草芽孢杆菌的抑制效果。设计不同浓度茶多酚溶液、不同p H和选择不同的金属离子,采用滤纸片法评判抑制效果。结果表明,茶多酚对供试菌有较强的抑菌活性,常用的防腐剂山梨酸钾对其抑制效果却不显著。茶多酚的浓度越高,抑菌活性越强。在弱碱性(p H=8)环境中的抑菌活性最强。茶多酚与金属离子络合对供试菌作用不明显的金属离子有K+、SO42-、Ba2+、Cl-;作用明显的金属离子有有Mn2+、Cu2+、Na+、Fe3+,其中茶多酚与Cu2+络合后对金黄色葡萄球菌的抑菌效果最好,提高了27.6%;茶多酚与Mn2+络合后对大肠杆菌的抑菌效果最好,提高了33.7%。     

肉桂醛及其复配单离香料对食品有害微生物的抑制作用研究

通过抑菌圈法测试肉桂醛、百里香酚、香芹酚、丁香酚、茴香脑和柠檬醛对几种常见有害微生物的抑菌敏感性。同时采用直接接触法测定最小抑菌浓度和最小杀菌浓度,研究这六种单离香料及复合单离香料对常见的食品腐败菌及致病菌的抗菌能力,并与常见防腐剂进行对比。研究结果表明：相对于细菌而言,肉桂醛对真菌抑菌能力更强,尤其对黄曲霉的抑菌效果最好;不同供试菌对不同单离香料的敏感度不同,其中大肠杆菌对所选单离香料的敏感度最低;百里香酚的综合抗菌能力最好,肉桂醛和香芹酚次之;但在试验浓度范围内,仅肉桂醛能将枯草芽孢杆菌杀死;复配精油对所有的供试菌（除了金黄色葡萄球菌）杀菌效果都有明显的提高,不同配比的复配精油对不同菌种的抗菌效果有所不同,肉桂醛-百里香酚复配精油对7种供试菌表现出了相加作用或者无关;复配精油的抗菌效果远强于苯甲酸钠和山梨酸钾这两种食品防腐剂。     

肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及抑菌机理研究

研究了肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌作用及其抑菌机理。本文采用滤纸片扩散法测定抑菌圈大小,双倍稀释法测定最低抑菌浓度、最低杀菌浓度,以此评价肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌性,通过扫描电镜观察、胞膜通透性、胞膜完整性、膜电位实验,阐述肉桂醛抑菌的机理。结果表明:肉桂醛对大肠杆菌和金黄色葡萄球菌的抑菌圈分别为21.75 mm、29.37mm,最低抑菌浓度均为0.25μL/m L,最低杀菌浓度均为0.5μL/m L;肉桂醛破坏了菌体细胞的形态,出现形变;随着肉桂醛浓度的增大,悬液中相对电导率迅速升高,表明肉桂醛影响细菌的膜通透性,而成倍数增长的核酸、蛋白质含量表示胞膜的完整性遭到破坏,肉桂醛降低菌体膜电位,影响其代谢活性,从而抑制细菌生长。肉桂醛主要作用于细胞膜,适宜作为天然防腐剂,抑制食品中腐败菌和致病菌的生长,延长食品货架期。     

红黑二丸中甾醇类物质的抑菌活性

采用牛津杯法和菌饼法分别测定红黑二丸甾醇类物质对细菌和霉菌的抑菌活性,并测定其最低抑菌浓度(MIC)。结果表明：红黑二丸甾醇类物质对金黄色葡萄球菌、枯草芽孢杆菌、大肠杆菌、沙门氏菌、志贺氏菌、黑曲霉和橘青霉均有一定的抑制效果,当甾醇质量浓度为7.0mg/mL时,对金黄色葡萄球菌的抑制效果最好,其抑菌直径大于9mm。红黑二丸甾醇类物质对金黄色葡萄球菌的抑制作用最强,其MIC值为0.5mg/mL。不同质量浓度红黑二丸甾醇类物质对细菌的药效持久性随着时间的延长呈下降趋势,且质量浓度越高,抑菌作用越明显。     

茶多酚与茶皂素及其复配液的抑菌作用研究

采用牛津杯法,研究不同浓度茶皂素、茶多酚单独使用与复配使用对食品常见污染菌金黄色葡萄球菌和大肠杆菌的抑菌作用。结果表明,茶多酚、茶皂素及其复配液对金黄色葡萄球菌和大肠杆菌均有不同程度的抑制作用,差异具有统计学意义(p0.05),呈现随浓度增大其抑菌作用越强的趋势;茶皂素和茶多酚复配使用时表现出明显的协同抑菌作用,复配液抑菌效果与浓度成正相关,特别是一定浓度的茶皂素中复配不同浓度的茶多酚对两种菌的抑制作用明显强于同浓度茶皂素的抑菌活性;同时,同浓度的茶多酚、茶皂素及其复配液对大肠杆菌的抑制作用均强于对金黄色葡萄球菌的抑制作用。研究显示,茶多酚、茶皂素及其复配液均具有良好的抑菌效果,抑菌作用与浓度成正相关。     

绞股蓝中木脂素体外抗氧化及抑菌活性研究

干燥绞股蓝粉碎后用乙醇反复浸泡,合并浸泡液减压浓缩后多次反复用正相硅胶柱层析、反相硅胶(ODS-AQ)柱层析和凝胶LH-20柱层析进行分离,得3个纯化合物Ⅰ、Ⅱ、Ⅲ并对其体外抗氧化和抑菌作用进行研究。结果表明：结构鉴定表明3个化合物均为木脂素类物质。化合物Ⅲ对DPPH自由基有较强清除作用,化合物Ⅰ的清除能力较弱,而化合物Ⅱ在实验浓度范围内没有显示出清除DPPH自由基作用;3种化合物对金属的螯合能力都比较弱;化合物Ⅱ对变异链球菌有一定的抑制作用,对金黄色葡萄球菌有较强的抑制作用,而对大肠杆菌和沙门氏菌显示较弱的抑制作用;化合物Ⅲ对金黄色葡萄球菌、大肠杆菌和沙门氏菌仅显示出微弱的抑制作用,化合物Ⅰ也显示出与化合物Ⅲ相似的抑菌趋势,但作用更弱。     

Autoinducer-2 activity of gram-negative foodborne pathogenic bacteria and its influence on biofilm formation

ABSTRACT:  This study evaluated whether autoinducer-2 (AI-2) activity would be associated with biofilm formation by Salmonella and Escherichia coli O157:H7 strains on food contact surfaces. In study I, a Salmonella Typhimurium DT104 strain and an E . coli O157:H7 strain, both AI-2 positive, were individually inoculated into 50 mL of Luria–Bertani (LB) or LB + 0.5% glucose (LBG) broth, without or with stainless steel or polypropylene ( Salmonella ) coupons. At 0, 14 ( Salmonella ), 24, 48, and 72 h of storage (25 °C), cells in suspension and detached cells from the coupons, obtained by vortexing, were enumerated on tryptic soy agar. In study II, a Salmonella Thompson AI-2-positive strain and an AI-2-negative strain, and an E . coli O157:H7 AI-2-positive strain and an AI-2-negative strain were inoculated into LB broth with stainless steel coupons. Cells were enumerated as in study I. In both studies, AI-2 activity was determined in cell-free supernatants. Cell numbers of S . Typhimurium DT104 on biofilms were higher ( P < 0.05) in LB than those in LBG, while the E . coli O157:H7 strain showed no difference ( P ≥ 0.05) in biofilm cell counts between LB and LBG after storage for 72 h. Both S . Typhimurium DT104 and E . coli O157:H7 strains produced higher ( P < 0.05) AI-2 activity in LBG than LB cell suspensions. Cell counts of AI-2-positive and-negative S . Thompson and E . coli O157:H7 strains were not different ( P ≥ 0.05) within suspensions or coupons (study II). The results indicated that, under the conditions of this study, AI-2 activity of the pathogen strains tested may not have a major influence on biofilm formation on food contact surfaces, which was similar between AI-2-positive and -negative strains.     

酶标仪法快速评价香兰素的抑菌活性

采用96孔板在酶标仪上测定了大肠杆菌(E.coli)、金黄色葡萄球菌(S.aureus)、李斯特菌(L.mono)、沙门氏菌(S.enteritidis)和宋内氏菌(Sh.Sonnei)在不同浓度香兰素存在下的光学密度(optical density,OD)值,并绘制其OD-t生长曲线。受试菌生长曲线显示香兰素对E.coli,S.aureus,L.mono,S.enteritidis和Sh.Sonnei的最低抑菌浓度分别为1.6mg/mL,2.2mg/mL,1.0mg/mL,1.2mg/mL和1.6mg/mL。     

Antibacterial activity of bioconverted eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) against foodborne pathogenic bacteria

The antimicrobial activity of bioconversion extracts of EPA and DHA against a range of foodborne pathogenic bacteria was investigated. The bioconverted EPA and DHA exhibited antibacterial activities against four gram-positive bacteria, Bacillus subtilis, Listeria monocytogenes, Staphylococcus aureus (ATCC 6538) and S. aureus (KCTC 1916) and seven gram-negative bacteria, Enterobacter aerogenes, Escherichia coli, E. coli O157:H7, E. coli O157:H7 (human), Pseudomonas aeruginosa, Salmonella enteritidis and S. typhimurium. The growth inhibition by both bioconverted EPA and DHA was similar against gram-positive bacteria, while the bioconverted extract of DHA was more effective than EPA against gram-negative bacteria as determined by minimum inhibitory concentration.     

Interactions of high hydrostatic pressure, pressurization temperature and pH on death and injury of pressure-resistant and pressure-sensitive strains of foodborne pathogens

The objective of this study is to determine the interactions between high hydrostatic pressure, pressurization temperature, time and pH during pressurization on death and injury of pressure-resistant and pressure-sensitive strains of four foodborne pathogens: Staphylococcus aureus 485 and 765, Listeria ,monocytogenes CA and OH2, Escherichia coli O157:H7 933 and 931, Salmonella enteritidis FDA and Salmonella typhimurium E21274. Among these strains S. aureus 485, L. monocytogenes CA, E. coli O157:H7 933 and S. enteritidis FDA were reported to be more pressure-resistant than the respective strain of the same species (Alpas et al., 1999). In general, viability loss of all pathogens was enhanced significantly as the level of pressure and temperature were increased (P < 0.05). All the strains except S. aureus 485 demonstrated more than 8 log cycle reduction when pressurized at 345 MPa at 50 degrees C for 5 min. This strain seemed to be the most pressure-resistant strain within the conditions of the study. Pressurization in the presence of either citric or lactic acid increased the viability loss by an additional 1.2-3.9 log cycles at pH 4.5 for both acids at 345 MPa. This study has indicated that high hydrostatic pressure applied in conjunction with mild heat and acidity can be an effective method for inactivating pressure-resistant and pressure-sensitive strains of four foodborne pathogens in organic acid solutions. This combination treatment indicates possible pressure pasteurization applications to liquid foods that have low pH. reserved.     

葡萄柚籽提取物及其纳米乳对大肠杆菌和金黄色葡萄球菌生物菌膜的抑制作用

目的：研究葡萄柚籽提取物(grapefruitseedextract,GSE)及其纳米乳(grapefruitseedextract nanoemulsion,GNE)对大肠杆菌和金黄色葡萄球菌生物菌膜的抑制作用。方法：分析菌膜黏附菌数变化、胞外聚合物(extracellular polymeric substances,EPS)含量并进行微观结构观察,比较GSE和GNE对两菌菌膜(单种菌膜和混合菌膜)形成的抑制作用和已形成菌膜的清除效果。结果：与对照组相比,1/2最小抑菌浓度(minimum inhibitory concentration,MIC)GSE和GNE可以抑制两菌单种菌膜形成时黏附菌和EPS产生,且对金黄色葡萄球菌的抑制作用更强。扫描电子显微镜(scanning electron microcopy,SEM)和共聚焦激光扫描显微镜(confocal laser scanning microscope,CLSM)所观察到的微观结构变化也显示出GSE和GNE对两菌菌膜形成具有抑制作用。GSE和GNE对已形成菌膜也有良好清除效果,且对金黄色葡萄球菌菌膜的清除作用更强,但混合菌膜...     

培养条件对金黄色葡萄球菌-大肠杆菌混合生物被膜的影响

以常见食源性致病菌金黄色葡萄球菌和大肠杆菌为研究对象,采用微孔板法对混合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25 ℃或30 ℃条件下,采用质量分数0.8%的胰酶大豆肉汤（TSB）或0.8%的脑心浸出液（BHI）培养基培养时,生物被膜形成量较高;添加适量的葡萄糖、乳糖、麦芽糖和蔗糖可提高混合生物被膜形成能力;培养基中NaCl质量分数＞8%时,混合生物被膜的生长明显受到抑制。     

Biofilm formation by Staphylococcus aureus strains and their control by selected phytochemicals

Biofilm formation by 30 Staphylococcus aureus dairy isolates and their control by phytochemicals were investigated. The majority of strains were biofilm positive by phenotypic analysis. The nuc and icaA genes were present in 30 and 27 strains, respectively. In addition, 13 strains were positive for all nuc, clfA, fnbA and icaA genes. The antimicrobial and antibiofilm activities of citral, cinnamaldehyde, eugenol, farnesol, limonene and terpinen‐4‐ol were also evaluated for seven strains. It was shown that the use of farnesol, cinnamaldehyde or terpinen‐4‐ol at a concentration of 2 mg/mL could be at least 80% effective on S. aureus strains and their biofilms.     

Bactericidal activities of plant essential oils and some of their isolated constituents against Campylobacter jejuni,Escherichia coli,Listeria monocytogenes,and Salmonella enterica

An improved method of sample preparation was used in a microplate assay to evaluate the bactericidal activity levels of 96 essential oils and 23 oil compounds against Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica obtained from food and clinical sources. Bactericidal activity (BA50) was defined as the percentage of the sample in the assay mixture that resulted in a 50% decrease in CFU relative to a buffer control. Twenty-seven oils and 12 compounds were active against all four species of bacteria. The oils that were most active against C. jejuni (with BA50 values ranging from 0.003 to 0.009) were marigold, ginger root, jasmine, patchouli, gardenia, cedarwood, carrot seed, celery seed, mugwort, spikenard, and orange bitter oils; those that were most active against E. coli (with BA50 values ranging from 0.046 to 0.14) were oregano, thyme, cinnamon, palmarosa, bay leaf, clove bud, lemon grass, and allspice oils; those that were most active against L monocytogenes (with BA50 values ranging from 0.057 to 0.092) were gardenia, cedarwood, bay leaf, clove bud, oregano, cinnamon, allspice, thyme, and patchouli oils; and those that were most active against S. enterica (with BA50 values ranging from 0.045 to 0.14) were thyme, oregano, cinnamon, clove bud, allspice, bay leaf, palmarosa, and marjoram oils. The oil compounds that were most active against C. jejuni (with BA50 values ranging from 0.003 to 0.034) were cinnamaldehyde, estragole, carvacrol, benzaldehyde, citral, thymol, eugenol, perillaldehyde, carvone R, and geranyl acetate; those that were most active against E. coli (with BA50 values ranging from 0.057 to 0.28) were carvacrol, cinnamaldehyde, thymol, eugenol, salicylaldehyde, geraniol, isoeugenol, citral, perillaldehyde, and estragole; those that were most active against L monocytogenes (with BA50 values ranging from 0.019 to 0.43) were cinnamaldehyde, eugenol, thymol, carvacrol, citral, geraniol, perillaldehyde, carvone S, estragole, and salicylaldehyde; and those that were most active against S. enterica (with BA50 values ranging from 0.034 to 0.21) were thymol, cinnamaldehyde, carvacrol, eugenol, salicylaldehyde, geraniol, isoeugenol, terpineol, perillaldehyde, and estragole. The possible significance of these results with regard to food microbiology is discussed.     

苦瓜汁的抑菌活性及其热稳定性的研究

采用琼脂扩散法研究了苦瓜汁对大肠杆菌、金黄色葡萄球菌、枯草芽孢杆菌、沙门氏菌的抑菌活性。研究结果表明:苦瓜汁对四种菌均具有较好的抑菌活性,其中对大肠杆菌和沙门氏菌的抑菌活性明显强于对金黄色葡萄球菌和枯草芽孢杆菌的抑菌活性;在100℃以内,苦瓜汁具有良好的抑菌稳定性。