抗氧化乳酸菌L4的SOD活性及其发酵乳的抗氧化作用

从30株乳酸菌中筛选出的抗氧化活性相对较高的乳酸菌L3和L4进行实验,发现乳酸菌L4的抗H2O2的能力明显要高于乳酸菌L3和保加利亚乳杆菌。并检测到乳酸菌L4无细胞提取物SOD活性为(73.70±1.77)U/mg。但未检测到乳酸菌L3和L4具有GSH-Px活性。利用PCR技术扩增了乳酸菌L4的SOD基因,通过DNA序列测定,发现乳酸菌L4的SOD基因与E.coli的Mn-SOD基因有高度的同源性。并发现乳酸菌L4发酵乳的还原活性和螯合Fe2+作用均明显高于未发酵乳。     

产类细菌素乳酸菌的筛选及其生物学特性研究

采用平板稀释和CO2厌氧培养技术,从多种发酵食品中分离出158株乳酸菌。通过牛津杯双层平板扩散试验,筛选出1株有明显抑菌活性的乳酸菌R-6,经初步鉴定为乳酸乳杆菌(Lactobacillus sp.)。R-6发酵上清液用NaOH调节pH5.5,对指示菌Escherichi coli.仍有明显抑菌活性,过氧化氢酶作用后其抑菌效果基本不变,因此可以排除乳酸和过氧化氢的干扰;R-6培养液经胰蛋白酶和蛋白酶K处理后,抑菌活性明显降低,且超过100℃热处理其抑菌活性迅速丧失,证实所产抑菌物质确系多肽类细菌素。该细菌素在酸性条件下活性较强,对革兰氏阴性菌(E.coli)抑菌作用较强,对革兰氏阳性菌(Bacillus subtilis和Staphlococcus aureus)也有明显抑制,显示出一定的抗菌广谱性。     

传统腌渍蔬菜中抑制嗜水气单胞菌群体感应及生物膜形成乳酸菌的筛选

从传统腌渍蔬菜分离的乳酸菌中筛选对嗜水气单胞菌群体感应及生物膜形成具有抑制作用的菌株。采用牛津杯打孔法从21株乳酸菌中筛选出具有抑制活性的6株乳酸菌,其中分离自辽宁大连酸黄瓜的菌株DLH513效果较好。当菌株DLH513粗提物质量浓度为16.0 mg/mL时,对嗜水气单胞菌AHLs信号分子降解率为51.1%,对其生物膜抑制率为40.9%;当粗提物质量浓度为20.0 mg/mL时,可使其AHLs信号分子完全降解。应用不同蛋白酶处理菌株DLH513粗提物后,对嗜水气单胞菌群体感应无抑制作用,表明其粗提物具有蛋白特性;在40～121℃处理30 min,其粗提物仍具有抑制群体感应活性,表明其粗提物具有耐热特征;在pH 3.0～4.5范围,菌株DLH513粗提物表现出抑制群体感应活性,在酸性条件下较稳定。光镜和扫描电镜结果表明,菌株DLH513粗提物对嗜水气单胞菌生物膜形成有显著的破坏作用。经生理生化反应和16S r RNA鉴定菌株DLH513为植物乳杆菌。研究表明植物乳杆菌DLH513可作为革兰氏阴性菌群体感应的抑制剂,以期为研发一种新的用于控制引起食品腐败和食源性疾病的革兰氏阴性菌群体感应的抑制剂提供理论基础。     

ε-聚赖氨酸对大肠杆菌的抑菌机制

聚赖氨酸(ε-poly-L-lysine,ε-PL)是一种具有广谱抑菌性的聚阳离子多肽,目前已作为生物防腐剂被广泛应用。为揭示ε-PL的抑菌机理,以大肠杆菌(Escherichia coli)为模式菌株,研究了ε-PL作用下E.coli的生长曲线、存活率以及ε-PL对E.coli细胞表面疏水性、内外膜穿透活性的影响,并且利用扫描电子显微镜观察了E.coli细胞形态在ε-PL作用下的变化,探究了ε-PL处理后E.coli聚团黏连现象。结果表明,ε-PL对E.coli的抑菌活性具有浓度依赖性,与ε-PL浓度呈正相关,当ε-PL质量浓度达到100μg/m L时,有明显抑菌效果。研究还发现,ε-PL能够增强E.coli细胞表面疏水性及细胞内、外膜的通透性,并且改变E.coli细胞膜内外电势,使其细胞内容物如核酸、蛋白质等大量渗出,从而实现对E.coli的杀菌作用。基于上述实验结果推测,ε-PL可能是通过毡毯模型中描述的作用模式将E.coli细胞杀死。     

鱼类肠道中抑制哈维氏弧菌群体感应及生物膜形成的乳酸菌的筛选和鉴定

从鱼类肠道来源的乳酸菌中筛选对目标菌—哈维氏弧菌群体感应及生物膜形成具有抑制作用的菌株。采用牛津杯打孔法从30株乳酸菌中筛选5株具有抗群体感应活性的菌株,其中源自鲤鱼肠道的菌株LY3-1的抑制效果较好,抑菌圈直径达14.21 mm。当菌株LY3-1粗提物质量浓度为8.0 mg/mL时,目标菌酰基高丝氨酸内酯(AHLs)信号分子的降解率为41.7%,生物膜抑制率为69.8%;当粗提物质量浓度为16.0 mg/mL时,可完全降解AHLs信号分子,生物膜抑制率达90.6%。菌株LY3-1粗提物经蛋白酶处理,群体感应抑制活性丧失,表明该粗提物中抑制群体感应的活性物质是蛋白质类物质。粗提物经40～121℃处理30 min,其群体感应抑制活性无显著性差异(P0.05),说明其具有热稳定性;同时,该粗提物在pH 3.5～7.0范围具有群体感应抑制活性。光镜和扫描电镜结果表明:菌株LY3-1粗提物对哈维氏弧菌生物膜形态结构具有显著破坏作用。菌株LY3-1经生理生化反应和16S rRNA测序被鉴定为乳酸乳球菌,其可作为哈维氏弧菌群体感应抑制剂。本研究结果为研发革兰氏阴性菌群体感应抑制剂提供理论基础。     

产抑菌活性物质菌株的筛选及其抑菌机理的研究

从内蒙古锡林郭勒盟地区酸马奶酒中分离出的9株乳酸菌和5株酵母菌中筛选抑菌效果较好的菌株,并对其发酵液的抑菌机理进行研究。以金黄色葡萄球菌、肠炎沙门氏菌肠亚种和荧光假单胞菌作为指示菌,通过牛津杯琼脂扩散法筛选出乳酸菌E13和D6与酵母菌J10A1的共生发酵液具有较强的抑菌能力,比乳酸菌单独发酵抑菌效果分别增加2.48 mm和1.45 mm。两株乳酸菌产生的抑菌活性物质使沙门氏菌生长曲线延滞期延长,对数期缩短,对数期峰值降低;电解质、可溶性总糖外渗,导致菌液电导率和可溶性总糖含量增加;糖吸收利用能力下降,磷代谢先变缓慢,随后趋于平稳。E13产生的抑菌活性物质的抑菌性更强。结果表明,乳酸菌产生的抑菌活性物质,不仅破坏细菌的细胞壁和细胞膜结构,还会影响菌体细胞代谢,导致细菌无法进行正常的生长和繁殖,从而发挥抑菌作用。     

融合魏斯氏菌对单增李斯特菌生物膜形成的影响

从东北传统酸菜的12株乳酸菌中筛选对单增李斯特菌有较强拮抗作用的低温生长菌株,并分析其对单增李斯特菌生物膜形成的影响。首先测定乳酸菌菌株的低温生长特征和抑菌活性;然后采用定性法和定量法分析乳酸菌菌株对单核细胞增生李斯特菌生物膜形成和形态结构的影响;最终通过生理生化和16S rDNA测序对乳酸菌菌株进行鉴定。结果表明：菌株Z01在10℃低温下生长,培养72 h后OD595nm值增加0.23,且具有抗单增李斯特菌活性,抑菌圈直径达19.79 mm。菌株Z01粗提物的最小抑菌浓度（minimal inhibitory concentration,MIC）为16.0 mg/mL,当粗提物浓度为0.5 MIC和1.0 MIC时,对生物膜形成抑制率分别为59.33%和77.77%,对生物膜黏附细菌的抑制率分别为14.49%和26.44%。该菌株被鉴定为融合魏斯氏菌（Weissella confusa）,为研发在低温条件控制单核细胞增生李斯特菌的生物制剂奠定基础。     

传统发酵蔬菜中抑制嗜水气单胞菌群体感应及生物膜形成乳酸菌的筛选与鉴定

目的:从来源于传统发酵蔬菜的乳酸菌中筛选对嗜水气单胞菌群体感应及生物膜形成有抑制作用的菌株。方法:采用牛津杯打孔法筛选乳酸菌菌株,测定其对N酰基高丝氨酸内酯(AHLs)信号分子的降解率。利用96孔板法测定其对生物膜的抑制率,应用光镜和扫描电镜观察其对生物膜形成的影响。最终通过生理生化试验和16S rRNA序列分析鉴定乳酸菌菌株。结果:分离自安徽绩溪酸豆角的菌株AJS2-4对嗜水气单胞菌群体感应有抑制作用,当其代谢产物粗提物质量浓度为4 mg/mL时,对嗜水气单胞菌AHLs的降解率为49.36%,对其生物膜抑制率为32.25%;当其质量浓度达到8 mg/mL时,可使嗜水气单胞菌的AHLs完全降解。该粗提物经121℃处理30 min活性基本不变,蛋白酶处理使其活性完全丧失,可初步判定菌株AJS2-4粗提物中的抑制群体感应活性成分为蛋白类物质,且具有热稳定性。光镜结果显示:菌株AJS2-4粗提物可有效抑制嗜水气单胞菌生物膜的合成。扫描电镜结果显示:菌株AJS2-4粗提物不仅能有效降低其生物膜的生成量,还可使其结构破裂变得疏松。经生理生化和16S r RNA鉴定菌株AJS2-4为植物乳杆菌(Lactobacillus plantarum)。结论:从安徽绩溪酸豆角中获得1株抑制嗜水气单胞菌群体感应和生物膜形成的植物乳杆菌AJS2-4。     

筛选用于四川泡菜生物保鲜的产细菌素乳酸菌（英文）

从8 种中国传统四川泡菜中筛选产细菌素的乳酸菌,以用于四川泡菜的生物保鲜。从四川泡菜样品中共分离出227 株乳酸菌,并筛选出8 株能够产生细菌素类化合物抑制英诺克李斯特氏菌(Listeria innocua)、金黄色葡萄球菌(Staphylococcus aureus)、枯草芽孢杆菌(Bacillus subtilis)和蜡样芽孢杆菌(Bacillus cereus)生长的乳酸菌。其中Lactobacillus harbinensis B22、屎肠球菌E6(Enterococcus faecium E6)和植物乳杆菌E11(Lb. plantarum E11)能够产生抑制革兰氏阴性菌大肠杆菌(Escherichia coli)生长的细菌素类化合物。进一步研究表明,这3 株乳酸菌耐酸、耐高盐,能够在四川泡菜模拟培养基中生长并产生耐酸耐高温的细菌素类化合物。结果表明,Lactobacillus harbinensis B22、屎肠球菌E6和植物乳杆菌E11可用于四川泡菜的生物保鲜。     

筛选用于四川泡菜生物保鲜的产细菌素乳酸菌

从8 种中国传统四川泡菜中筛选产细菌素的乳酸菌,以用于四川泡菜的生物保鲜。从四川泡菜样品中共分离出227 株乳酸菌,并筛选出8 株能够产生细菌素类化合物抑制英诺克李斯特氏菌（Listeria innocua）、金黄色葡萄球菌（Staphylococcus aureus）、枯草芽孢杆菌（Bacillus subtilis）和蜡样芽孢杆菌（Bacillus cereus）生长的乳酸菌。其中Lactobacillus harbinensis B22、屎肠球菌E6（Enterococcus faecium E6）和植物乳杆菌E11（Lb. plantarumE11）能够产生抑制革兰氏阴性菌大肠杆菌（Escherichia coli）生长的细菌素类化合物。进一步研究表明,这3 株乳酸菌耐酸、耐高盐,能够在四川泡菜模拟培养基中生长并产生耐酸耐高温的细菌素类化合物。结果表明,Lactobacillus harbinensis B22、屎肠球菌E6和植物乳杆菌E11可用于四川泡菜的生物保鲜。     

类细菌素高产菌CF10的筛选诱变及发酵条件的研究

采用纸片法初筛和杯碟法复筛自黄水中分离出一株抗生物质产生菌CF10,经鉴定为布氏乳杆菌(Lactobacillusbuchneri)。在排除酸性末端产物及过氧化氢的干扰后,CF10菌株发酵液对金黄色葡萄球菌(Staphylococcusaureus)和枯草芽孢杆菌(Bacillussubtilis)等革兰氏阳性菌、大肠杆菌(Escherichiacoli)和绿脓杆菌(Pseudomonaspyocyanea)等革兰氏阴性菌、K酵母(SaccharomycescerevisiaeK)和某些真菌有强烈的抑制作用。经紫外线照射(UV)和硫酸二乙酯(DES)多轮复合诱变,CF10发酵液相对效价较未诱变前提高了258%且具有良好的传代稳定性。通过对该菌株产类细菌素发酵条件的研究发现,以2%麦芽糖为碳源、1%大豆蛋白胨加0.5%酵母粉为氮源,培养温度37℃,初始pH6.0～6.5,培养时间48h,接种量1%,厌氧条件下,有微量K+、Mg2+和Mn2+等金属离子存在,CF10所产类细菌素的抑菌活性最高。     

拮抗大肠杆菌的海洋微生物的筛选与鉴定

该研究采用涂布平板法、对峙培养法及琼脂扩散法从北冰洋沉积物样品中分离、筛选出对大肠杆菌（Escherichia coli）具有良好拮抗作用的一株菌株,通过对其菌株形态进行观察、分析其生理生化试验结果以及进行分子生物学技术检测,进行分类鉴定,并进行了抑菌谱研究。结果表明,从北冰洋沉积物样品中共分离纯化出97株菌株,其中21株菌株对大肠杆菌有一定的拮抗作用,且1株菌株拮抗效果最好,编号为105号,平均抑菌圈直径为（19.3±1.0） mm。该菌株被鉴定为萎缩芽孢杆菌（Bacillus atrophaeus）,抗菌谱较为广泛,对大肠杆菌、铜绿假单胞菌、鼠伤寒沙门氏菌、肺炎克雷伯氏菌都具有抑制作用。     

LACTOBACILLUS CURVATUS PRODUCES A BACTERIOCIN-LIKE AGENT ACTIVE AGAINST GRAM-NEGATIVE PATHOGENIC BACTERIA

Isolates from fermented foods were screened for antimicrobial activity against gram‐negative bacteria. The most active isolate was identified as a Lactobacillus curvatus by biochemical analysis and ribotyping, and the isolate was designated as OSY‐HJC6. Lactobacillus curvatus OSY‐HJC6 was further tested for intracellular and extracellular production of antimicrobial agents. A reduction of > 8 log₁₀ cfu/mL was observed when cell suspensions of Salmonella enterica serovar Enteritidis and Escherichia coli O157:H7 were treated with equal volumes of Lb. curvatus culture supernatant. Gram‐positive bacteria were not sensitive to the culture supernatant, but antimicrobial activity was detected when the cell extract was tested against several gram‐positive and gram‐negative bacteria. Culture supernatant and cell extract retained the antimicrobial activity after heating at 60–100C for 10 min but not after protease treatment. The cell extract of Lb. curvatus retarded the growth of E. coli p220 in broth medium and food extracts (i.e., bacteriostatic action) but showed bactericidal activity against the bacterium in phosphate buffer.     

副干酪乳杆菌Z17-壳聚糖复配对大肠杆菌O157:H7的抑菌效果及作用机制

目的：研究副干酪乳杆菌Z17-壳聚糖复配对草莓中大肠杆菌O157:H7抑菌活性及作用机制。方法：采用流式细胞术、傅里叶变换红外光谱、拉曼光谱及扫描电子显微镜技术分析副干酪乳杆菌Z17-壳聚糖对大肠杆菌O157:H7细胞膜的影响。结果：质量分数1.0%壳聚糖溶液与副干酪乳杆菌Z17复配处理能有效去除草莓上的大肠杆菌O157:H7,减菌率达99%;壳聚糖溶液与副干酪乳杆菌Z17共同作用3 h使大肠杆菌O157:H7 DNA胞外释放量达（381.00±3.53）ng/μL,细胞膜破损率为58.3%;细胞壁膜中脂肪酸、蛋白、肽聚糖、糖苷环、多糖结构成分被破坏;细胞膜局部位移变薄,大分子物质黏附于菌体细胞表面,细胞表面出现孔洞,胞内物质泄漏,最终导致菌体死亡。结论：副干酪乳杆菌Z17-壳聚糖能够有效地抑制草莓中大肠杆菌O157:H7,其抑菌作用靶点为大肠杆菌O157:H7的细胞膜,研究可为大肠杆菌O157:H7的生物防治提供参考。     

丁香酚对多重耐药大肠杆菌的抑菌活性及其作用机制研究

为研究丁香酚对多重耐药大肠杆菌(Multidrug-resistant Escherichia coli,MDR E.coli)的抑菌活性,利用微量二倍稀释法和琼脂扩散法确定丁香酚对多重耐药大肠杆菌的最低抑菌浓度(Minimum inhibitory concentration,MIC)和最低杀菌浓度(Minimum bactericidal concentration,MBC),并利用紫外分光光度法、考马斯亮蓝法等方法初步分析其作用机制。结果表明,丁香酚对MDR E.coli的MIC和MBC分别为2.50 mg/mL和5.00 mg/mL;丁香酚可延长MDR E.coli迟缓期进入对数生长期的进程,改变菌体结构,增加菌株可溶性蛋白的含量和胞外核酸的量,增大菌体培养液中的电导率,对MDR E.coli具有较强的抑菌作用,这些作用可能归因于丁香酚对其细胞结构的破坏。本研究为临床有效缓解或解决多重耐药大肠杆菌的耐药、感染和致死率等问题提供新的思路、新途径,并为其在医药和食品开发领域的应用奠定理论基础。     

Inhibitory activity of Bifidobacterium longum HY8001 against Vero cytotoxin of Escherichia coli O157:H7.

Vero cytotoxin (VT)-producing Escherichia coli (VTEC), such as E. coli O157:H7, are emerging foodborne pathogens worldwide. VTs are associated with hemorrhagic colitis and hemolytic uremic syndrome in humans. Attachment of the B subunit of VTs to its receptor, globotriaosylceramide (Gb3), at gut epithelium is the primary step and, consequently, the A subunit of VTs inhibits protein synthesis in the target cell. Proinflammatory cytokines, such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, up-regulate Gb3 expression, increase sensitivity to VTs, and enhance VT action in developing disease. Currently, there is a growing interest in probiotics, given the increasing occurrence of antibiotic-resistant bacteria. In particular, much work on bifidobacteria among probiotics, regarded as microorganisms targeted for technological and therapeutic applications, has been performed. In Korea, the neutralizing effect of the culture supernatant of Bifidobacterium longum HY8001, Korean isolate, against the VTs from E. coli O157:H7 was found. Therefore, this study focused on the raveling of the inhibitory effect of B. longum HY8001 against VTs, through the interference B subunit of VTs and Gb3 interaction. Mice were inoculated intragastrically with B. longum HY8001 culture supernatant before and after challenge with E. coli O157:H7. Control mice were inoculated intragastrically only with E. coli O157:H7. Cytokine, TNF-alpha, and IL-1beta levels in sera and expression of their mRNA were decreased, and expression of Gb3 in renal tubular epithelial cells was reduced in mice treated with B. longum HY8001 culture supernatant. In competitive enzyme-linked immunosorbent assays (ELISAs), the culture supernatant of B. longum HY8001 primarily binds VTs to interfere the VTs with Gb3 interaction. These results suggest that soluble substance(s) in B. longum HY8001 culture supernatant may have inhibitory activity on the expression of Gb3, VT-Gb3 interaction, or both. Further study should be done to elucidate the property of soluble substances in B. longum HY8001 culture supernatant.     

Effect of tannins on the in vitro growth of Escherichia coli O157:H7 and in vivo growth of generic Escherichia coli excreted from steers

The effect of commercially available chestnut and mimosa tannins in vitro (experiment 1) or in vivo (experiment 2) on the growth or recovery of Escherichia coli O157:H7 or generic fecal E. coli was evaluated. In experiment 1, the mean growth rate of E. coli O157:H7, determined via the measurement of optical density at 600 nm during anaerobic culture in tryptic soy broth at 37 degrees C, was reduced (P < 0.05) with as little as 400 microg of either tannin extract per ml of culture fluid. The addition of 200, 400, 600, 800, and 1,200 microg of tannins per ml significantly (P < 0.01) reduced the specific bacterial growth rate when compared with the nontannin control. The specific growth rate decreased with increasing dose levels up to 800 microg of tannins per ml. Bacterial growth inhibition effects in chestnut tannins were less pronounced than in mimosa tannins. Chestnut tannin extract addition ranged from 0 to 1,200 microg/ml, and a linear effect (P < 0.05) was observed in cultures incubated for 6 h against the recovery of viable cells, determined via the plating of each strain onto MacConkey agar, of E. coli O157:H7 strains 933 and 86-24, but not against strain 6058. Similar tests with mimosa tannin extract showed a linear effect (P < 0.05) against the recovery of E. coli O157:H7 strain 933 only. The bactericidal effect observed in cultures incubated for 24 h with the tannin preparations was similar, although it was less than that observed from cultures incubated for 6 h. When chestnut tannins (15 g of tannins per day) were infused intraruminally to steers fed a Bermuda grass hay diet in experiment 2, fecal E. coli shedding was lower on days 3 (P < 0.03), 12 (P = 0.08), and 15 (P < 0.001) when compared with animals that were fed a similar diet without tannin supplementation. It was concluded that dietary levels and sources of tannins potentially reduce the shedding of E. coli from the gastrointestinal tract.     

拮抗阪崎肠杆菌乳酸菌的筛选鉴定及抑菌特性

阪崎肠杆菌（Enterobacter sakazakii）是引起新生儿败血症、脑膜炎和坏死性小肠结肠炎的条件致病菌,感染后死亡率高达80%。实验采用双层琼脂扩散法从淡水鱼肠道（19 株）和泡菜（7 株）中筛选出1 株来源于鲤鱼肠道的对Enterobacter sakazakii（106 CFU/mL）具有较强拮抗作用的乳酸菌菌株LY-4。结果表明,抑菌活性物质存在于乳酸菌无细胞上清液（cell free supermatant,CFS）中,抑菌最佳培养时间为28 h。CFS经胃蛋白酶处理可完全丧失抑菌活性,中性蛋白酶和木瓜蛋白酶处理后抑菌活性降至76.44%和54.38%,对α-淀粉酶不敏感;在pH 3.0～4.5范围内保持抗菌活性稳定;经40～80 ℃范围内处理2 h后其拮抗活性基本不变,100 ℃和121 ℃处理2 h后活性降至79.57%和75.71%。初步判定菌株LY-4产生的抑菌物质为非糖基化类细菌素,并筛选出初步纯化抑菌物质的最佳萃取剂为乙酸乙酯,粗提物的最小抑菌浓度为6.0 mg/mL。经生理生化和16S rDNA鉴定为植物乳杆菌（Lactobacillus plantarum）。     

Lactobacillus delbrueckii subsp lactis strain CIDCA 133 inhibits nitrate reductase activity of Escherichia coli

The aim of the present work was to investigate the effect of strain CIDCA 133 on the nitrate reductase activity of a non-pathogenic Escherichia coli strain. Suspensions containing different ratios of the strains under study were coincubated in MRS or MRS without glucose. In some experiments lactobacilli were killed by UV treatment. The nitrate reductase activity was determined by using a diazotization reaction for nitrite. Presence of live lactobacilli leads to a dose-response diminution in the specific nitrate reductase of E. coli even when no acidification occurred. Killing of lactobacilli by UV treatment completely abolished the anti-nitrate reductase effect. In addition, the effect was only partially observed with filtered spent culture supernatants of lactobacilli. Lactobacillus delbrueckii subsp lactis strain CIDCA 133 is able to antagonize the nitrate reductase activity of E. coli. This effect is neither due to a diminution of the viability of E. coli nor is depending on the acidification of the medium by the lactobacilli. Viability is needed for maximal anti-nitrate reductase activity. Modulation of undesirable enzymatic activities of intestinal microorganisms by means of selected microorganisms constitutes a further insight on the mechanisms by which probiotics lead to beneficial effects. Administration of probiotic strains able to modulate microbial intestinal activities could lead to a protection of the host against harmful effects of some members of the intestinal microflora.     

Antimicrobial activity of nutmeg against Escherichia coli O157

We examined the difference between Escherichia coli O157 and non-pathogenic E. coli in their tolerance to spices. Various spices (5 g each) were homogenized at 25 degrees C for 10 min with 5 ml of 70% ethyl alcohol, and the supernatant solutions obtained by centrifugation were used as spice extracts. When the E. coli strains were incubated with each spice extract at concentrations of 0.01% and 0.1%, a noteworthy difference was observed between the O157 and non-pathogenic strains in their tolerance to nutmeg. The populations of the non-pathogenic strains could not be reduced, but those of the O157 strains were remarkably reduced. Antibacterial activity by the nutmeg extract was also found against the enteropathogenic E. coli O111, but not against enterotoxigenic (O6 and O148) and enteroinvasive (O29 and O124) E. coli. When we examined the antibacterial effect of volatile oils in nutmeg on the O157 and non-pathogenic E. coli strains, all O157 strains tested were found to be more sensitive to beta-pinene than non-pathogenic E. coli strains.