酸奶中乳酸菌的药物敏感性分析

目的:分析和鉴定不同产地酸奶中乳酸菌对一些常用抗生素的敏感性,指导合理使用抗菌药物与合理使用乳酸菌发酵制品。方法:利用改良的MRS培养基从各地酸奶中分离获得乳酸菌,然后采用琼脂稀释法,对分离获得的18株保加利亚乳杆菌和28株嗜热链球菌对11种常用抗生素的药物敏感性进行检测和分析。结果:同一菌株对不同的抗生素具有不同的药物敏感性,不同菌株对同一种抗生素也显示出不同的敏感性。结论:乳酸菌对常用抗生素的多重耐药已成为普遍现象,不同来源的菌株表现出了不同的耐药性。      

细菌药物敏感性实验方法研究进展

致病菌的耐药性已成为世界范围内的公共卫生和安全问题,如何对致病菌的耐药性进行准确快速的检测是许多微生物科研人员和医疗工作者共同面临的难题。根据近年国内外有关研究资料与报道,对于细菌耐药性的检测和分析主要通过对细菌进行药物敏感性实验来执行。目前用于细菌药敏性实验的方法主要包括:肉汤稀释法、琼脂稀释法、K-B纸片法和E-test实验等。文中就以上几种细菌药敏性实验方法的原理、步骤及优缺点进行了概述,并对各种实验方法的应用进行了举例分析。     

细菌药物敏感性实验方法研究进展

致病菌的耐药性已成为世界范围内的公共卫生和安全问题,如何对致病菌的耐药性进行准确快速的检测是许多微生物科研人员和医疗工作者共同面临的难题。根据近年国内外有关研究资料与报道,对于细菌耐药性的检测和分析主要通过对细菌进行药物敏感性实验来执行。目前用于细菌药敏性实验的方法主要包括:肉汤稀释法、琼脂稀释法、K-B纸片法和E-test实验等。文中就以上几种细菌药敏性实验方法的原理、步骤及优缺点进行了概述,并对各种实验方法的应用进行了举例分析。      

不同来源食品级乳酸菌及双歧杆菌对乳酸链球菌素敏感性的研究

目的:研究不同来源的食品级乳酸菌和双歧杆菌对乳酸链球菌素(nisin)的敏感性,为构建以nisin作为食品级筛选标记的受体乳酸菌表达系统以及筛选食品发酵、保鲜与贮藏过程中的nisin抗性乳酸菌提供科学依据.方法:采用试管稀释法研究不同来源的食品级的18株乳酸球菌、15株乳酸杆菌和5株双歧杆菌对nisin的敏感性.结果:大部分乳球菌和部分乳杆菌对nisin不敏感,但乳酸乳球菌(Lactococcus lactis)ML0230、99210,肠膜明串珠菌葡聚糖亚种(Leuconostoc mesenteroides subsp dextranicum)AS 1.2141T,嗜酸乳杆菌(Lactobacillus acidophilus)La1,德氏乳杆菌保加利亚亚种(Lactobacillus delbrueckii subsp bulgaricus)S-1、DR、LD、AS 1.2625T,长双歧杆菌(Bifidobacterium longum)Blm对nisin非常敏感.在nisin质量浓度为5 μg/mL(IU/mL)时即可抑制其生长.结论:初步筛选出17株以nisin作为食品级筛选标记的受体乳酸菌,同时筛选出21株食品发酵、保鲜与贮藏过程中的nisin抗性乳酸菌.     

三株食用乳酸菌对抗生素的药敏性研究

乳酸菌是人体胃肠道内的益生菌,抗生素的施用可能导致乳酸菌功能的降低或丧失。为了了解乳酸菌对药物的敏感性,以便指导人们合理使用乳酸菌制品和施药,本实验通过对保加利亚乳酸杆菌、嗜热链球菌和乳酸链球菌三株常用乳酸菌对氨苄青霉素、氯霉素、红霉素、链霉素和四环素等五种医疗常用抗生素的敏感性进行研究,结果显示,不同的乳酸菌对不同的抗生素表现出不同的敏感性。研究结果提示人们在使用乳酸菌制品时,要注意施用药物对乳酸菌的影响。     

三株食用乳酸菌对抗生素的药敏性研究

乳酸菌是人体胃肠道内的益生菌,抗生素的施用可能导致乳酸菌功能的降低或丧失。为了了解乳酸菌对药物的敏感性,以便指导人们合理使用乳酸菌制品和施药,本实验通过对保加利亚乳酸杆菌、嗜热链球菌和乳酸链球菌三株常用乳酸菌对氨苄青霉素、氯霉素、红霉素、链霉素和四环素等五种医疗常用抗生素的敏感性进行研究,结果显示,不同的乳酸菌对不同的抗生素表现出不同的敏感性。研究结果提示人们在使用乳酸菌制品时,要注意施用药物对乳酸菌的影响。      

富源酸菜源乳酸菌分离鉴定及益生特性研究

目的:从自然发酵富源酸菜中分离乳酸菌,研究其益生特性,为乳酸菌益生菌制剂研发提供基础数据.方法:采集自然发酵的富源酸菜样品,使用MRS培养基分离乳酸菌,研究其耐酸、耐胆盐、抑菌活性和抗生素敏感性等益生特性,并采用16S rDNA基因序列分析法进行鉴定.结果:分离得到MH-3、MH-4、ZY-3和YS-24株菌株,16S...     

健康人体及保健品中乳酸菌和双歧杆菌的抗药性分析

目的:研究常用抗生素对来自健康人体和保健品的乳酸菌的影响.为构建乳酸菌和双歧杆菌食品级基因克隆和表达系统,为研制益生菌食品级微生态制剂而筛选无耐药性受体菌株和安全菌株.为乳酸菌的抗性筛选提供科学依据.方法:采用标准药敏纸片琼脂扩散法(K-B法),以金黄色葡萄球菌ATCC 25923为标准对照菌株,研究15株乳酸球菌,14株乳酸杆菌,5株双歧杆菌对8大类19种常用抗生素的敏感性.结果:15株乳酸球菌对氨苄西林、青霉素G、头孢霉素、头孢曲松、卡那霉素、四环素、红霉素、氯霉素均敏感或中度敏感:对磺胺、多黏菌素B均耐药;对其它抗生素表现出不同药敏性.14株乳杆菌都对氨苄西林、青霉素G、头孢霉素、卡那霉素、红霉素、四环素、氯霉素敏感或中度敏感;对磺胺、甲氧嘧啶、多黏菌素B均耐药:对其它表现出不同药敏性.5株双歧杆菌均对氨苄西林、青霉素G、头孢霉素、卡那霉素、甲氧苄氨嘧啶、红霉素、四环素、氯霉素敏感或中度敏感;对庆大霉素、阿米卡星、链霉素、磺胺、杆菌肽、环丙沙星均耐药;对其它抗生素表现出不同药敏性.     

酸奶中乳酸菌稳定性的研究

以酸奶中乳酸菌为研究对象,研究在酸奶的加工贮藏过程中温度、pH值等环境因素对乳酸菌稳定性的影响.研究发现,酸奶加工过程中可加入1%的食盐和5%的海藻糖,并且可适当提高脂类和蛋白质的含量,在酸奶装罐前应将其pH值调至4.0左右,将成品贮藏在2℃～7℃环境下,以求最大限度的保持酸奶中活乳酸菌的数目.     

Nisin和山梨酸钾对酸奶中乳酸菌及杂菌的体外抑菌实验

本文采用稀释平板法,在pH6.0条件下,测定Nisin、山梨酸钾及二者复配后对酸奶中的乳酸菌、芽孢杆菌、大肠杆菌、金黄色葡萄球菌、沙门氏菌、酵母菌、霉菌的抑制作用.结果表明培养相同时间,随着防腐剂浓度的升高,Nisin、山梨酸钾及二者复配对乳酸菌抑菌率上升;相同防腐浓度,随着培养时间的延长,Nisin、山梨酸钾及二者复配对乳酸菌抑菌率下降.Nisin对所试乳酸菌菌株具有一定的抑菌效果,而山梨酸钾在16h内具有一定的抑菌效果.Nisin、山梨酸钾二者复配抑菌效果明显优于单独使用,Nisin0.125g/kg、山梨酸钾0.5g/kg二者复配,16h、48h对乳酸菌的抑菌率分别为80.8%、46.7%.实验中的各个防腐浓度,Nisin、山梨酸钾单独或复配使用对芽孢杆菌等杂菌抑菌几乎无效果.     

5株发酵食品源乳酸菌的抗药性分析

以实验室前期分离自混合果蔬酵素的植物乳杆菌(Lactobacillus plantarum S)、分离自树莓酵素的植物乳杆菌(L. plantarum WD)和分离自不同奶制品的保加利亚乳杆菌(L. bulgaricus LB-DR)、鼠李糖乳杆菌(L. rhamnosus Lr-05-281)与干酪乳杆菌(L. casei D-400)5株乳酸菌为研究对象,采用平板药敏纸片扩散法、PCR及RT-PCR技术从表型、基因型以及基因表达几个方面分析菌株的抗药性。结果表明5株菌对氨基糖苷类、喹诺酮类、糖肽类抗生素、多粘菌素B均有抗性;对大环内酯类、四环素类、磺胺类抗生素、呋喃妥因均敏感,并有较为相似的耐药谱;而对不同的β-内酰胺类抗生素敏感性不同;5株乳酸菌均含有质粒,供试的12个抗性基因中,在质粒上检测到erm、aph、vanⅠ、aacⅠ4种抗性基因,基因组DNA上检测到aph、erm、vanⅠ、blaⅡ、aacⅠ、aacⅡ6种抗性基因。部分抗性基因在MRS和加抗生素的MRS培养下会表达,不表达的抗性基因在相应抗生素诱导的条件下其抗性基因不表达。L. plantarum WD菌株质粒上因只含一种vanⅠ抗性基因,其应用安全性较好。     

乳酸菌细菌素抑菌特性及在食品中的应用研究进展

乳酸菌细菌素是细菌在核糖体上合成的具有抗菌活性的多肽类物质,这些细菌素能杀灭或抑制引起食品腐败的细菌的繁殖,可作为天然的食品防腐剂在食品中应用。该文综述了乳酸菌细菌素的分类、国内外研究现状、抑菌特性及应用等方面的最新研究进展,并对乳酸菌细菌素未来研究趋势进行简要分析,对乳酸菌细菌素在食品中的应用有一定参考价值。     

Antimicrobial activity of crude extracts from actinomycetes against mastitis pathogens

The emergence of antimicrobial resistance to commonly used antibiotics has necessitated the development of new antimicrobial products. Crude extracts produced by actinomycetes contain antimicrobial metabolites that can inhibit bacterial growth. The objective of our study was to evaluate the antimicrobial activity of crude extracts (Caat1–54 and CaatP5–8) produced by actinomycetes against isolates of Staphylococcus aureus, Staphylococcus chromogenes, Streptococcus dysgalactiae, and Streptococcus uberis, which were obtained from the milk of cows affected by mastitis in 23 dairy herds. Twenty isolates of each bacterial species were used to define minimum inhibitory concentrations (MIC) of both crude extracts and ceftiofur (positive control). The MIC₅₀ and MIC₉₀ were defined at the concentration required to inhibit the growth of 50 and 90% of bacterial isolates tested, respectively. The MIC results were evaluated by survival analysis. Staphylococcus aureus isolates presented MIC₉₀ of Caat 1–54 ≥6.25 µg/mL, ceftiofur ≥12.5 µg/mL, and Caat P5–8 ≥100 µg/mL. Streptococcus uberis presented MIC₉₀ of ceftiofur ≥0.39 µg/mL, Caat 1–54 ≥50 µg/mL, and Caat P5–8 ≥100 µg/mL. Staphylococcus chromogenes isolated from subclinical mastitis presented MIC₉₀ of Caat 1–54 ≥0.78 µg/mL and ceftiofur and Caat P5–8 of ≥6.25 and ≥100 µg/mL, respectively. Streptococcus dysgalactiae isolated from clinical mastitis presented similar MIC₉₀ values between antimicrobials tested (ceftiofur, Caat 1–54, and Caat P-58), but these values (≥100 µg/mL) were higher than the values obtained from other pathogens evaluated in the present study. Our results indicate that Caat 1–54 and Caat P5–8 crude extracts present in vitro antimicrobial activity against isolates of Staph. aureus, Staph. chromogenes, Strep. dysgalactiae, and Strep. uberis isolated from clinical and subclinical mastitis.     

Minimum inhibitory concentrations of frequently used antibiotics against Escherichia coli and Trueperella pyogenes isolated from uteri of postpartum dairy cows

The objective of this study was to determine minimum inhibitory concentrations (MIC) of frequently used antimicrobials for Escherichia coli and Trueperella pyogenes isolated from postpartum bovine uteri of cows with acute puerperal metritis (APM, n = 67), cows suspected to have APM (n = 37), and healthy cows (n = 37) and to evaluate possible differences in MIC according to clinical signs. Cows with APM had reddish-brown, fetid vaginal discharge and rectal temperature (RT) ≥39.5°C within 21 d in milk; cows suspected to have APM had either reddish-brown, fetid vaginal discharge or RT ≥39.5°C within 21 d in milk; and healthy cows had neither fetid discharge nor RT ≥39.5°C. Samples were collected from cows on commercial dairy herds (n = 7) using the cytobrush technique. A total of 37 T. pyogenes isolates and 85 E. coli isolates were tested. Ceftiofur, a third-generation cephalosporin that is often used to treat APM, was the focus of analysis. Trueperella pyogenes and E. coli were isolated more often from samples of cows with APM (46 and 90%, respectively) compared with samples from healthy cows (19 and 54%, respectively). Regarding cows suspected to have APM, T. pyogenes and E. coli were numerically more often isolated (30 and 70%, respectively) than in healthy cows (19 and 54%, respectively). Minimum inhibitory concentrations of ceftiofur were low. For T. pyogenes and E. coli, MIC₅₀ (concentration that inhibited growth of 50% of isolates) were 0.25 and 0.5 µg/mL and MIC₉₀ (concentration that inhibited growth of 90% of isolates) were 0.5 and 1 µg/mL, respectively. Although ceftiofur inhibited all T. pyogenes at the highest concentration tested (64 µg/mL), the growth of 5.9% of E. coli was not impaired. Recently, ampicillin has been suggested as an alternative treatment for APM. Although the T. pyogenes isolates exhibited low MIC in general (MIC₅₀ ≤0.015 µg/mL and MIC₉₀ = 0.06 µg/mL) and 81.1% of all T. pyogenes could be inhibited at the lowest ampicillin concentration tested, 11.8% of the E. coli isolates were not impaired at the highest concentration (64 µg/mL) tested in this study. The MIC₅₀ and MIC₉₀ of E. coli were 4 and ≥128 µg/mL, respectively. We detected no difference in the MIC distributions of ceftiofur or ampicillin among isolates from the 3 APM groups. In summary, E. coli with high MIC against ceftiofur as well as against ampicillin were found in this study.     

具有ACE抑制活性乳酸菌菌株的筛选与鉴定

以ACE抑制活性和蛋白水解活性为检测指标,选择138株乳酸菌为出发菌株,筛选出具有强ACE抑制活性的乳酸菌菌株.结果表明,筛选出具有强ACE抑制活性的4株乳酸菌,其中3株菌为瑞士乳杆菌,1株菌为干酪乳杆菌.瑞士乳杆菌KLDS1.0485和干酪乳杆菌KLDS1.0486比例为1:1,制成的发酵乳ACE抑制活性可达到61.55%.因此,组合瑞士乳杆菌KLDS1.0485和干酪乳杆菌KLDS1.0486可作为制备乳源ACE抑制肽的优良菌株.     

发酵乳制品中乳酸菌的流式检测方案探索与研究

目的 建立基于流式细胞术的发酵乳制品中乳酸菌快速计数方法, 实现发酵乳制品中乳酸菌的快速定量检测。方法 使用5(6)-羧基荧光素二乙酸酯（5-(and 6)-Carboxyfluorescein diacetate,cFDA） 和碘化丙啶（Propidium iodid,PI）2种荧光染料对乳酸菌进行染色,经流式细胞仪检测乳酸菌的荧光信号,从而实现细菌定量计数。在分析过程中对染色剂浓度、荧光通道阈值进行优化,并将流式计数结果与现行国标方法进行对比研究。结果 在样品浓度为104 CFU/mL(g)时,通过0.05 μg/mL的PI和10 μmol/L的cFDA染色,在绿色荧光通道增益为100,红色荧光通道增益达到1000时,能够达到最佳的流式检测条件,且样品检测结果与现行国标检测方法存在显著的正相关关系（P<0.01）,2种方法测试结果相关系数值为0.949。结论 流式细胞术具有灵敏度高、检测时间短、稳定性高、重现性好等优点,对于货架期普遍较短,放行压力大的乳制品生产企业来说,能够缩短检测时间,实现产品快速放行上架。     

乳酸菌抗菌肽(细菌素)抗菌机理的研究进展

乳酸菌抗菌肽是乳酸菌代谢过程产生的一类具有活性的多肽或蛋白质物质,可抑制或杀死食品中的病原菌或腐败菌。很多乳酸菌产生的抗菌肽不仅抑制相关菌种,还包括很多种类的革兰氏阳性腐败菌和食源性致病菌。在抗菌肽被广泛使用之前很久科学家们已经发现了某些细菌的抑菌活性,甚至在抗菌肽生产菌没有确定的条件下就已经将抗菌肽应用于发酵食品中。近几年,乳酸菌对其他细菌的拮抗作用的机理研究得最多的是乳酸菌抗菌肽。乳酸菌抗菌肽在食品行业中具有广泛的应用前景,它被认为是一种"天然"的食品添加剂而容易被人们接受。本文首先对所有乳酸菌抗菌肽的作用机制进行简短叙述,总结出乳酸菌抗菌肽抑菌机制的五种模型,分别是:"桶板"模型、"楔"模型、"虫孔"模型、"毯式"模型、"凝聚"模型。以此为基础,对不同种类的乳酸菌抗菌肽抑菌机制分别进行论述,最后对其最新进展进行总结。     

Antimicrobial Efficacy of an Array of Essential Oils Against Lactic Acid Bacteria

The essential oils of clove bud, cinnamon bark and thyme, and their individual compounds including allyl isothiocyanate (AIT), carvacrol, cinnamaldehyde, cinnamic acid, eugenol, and thymol were initially assessed for antimicrobial activity against 9 lactic acid bacteria (LAB) species. Carvacrol and thymol were the most inhibitory with MICs of 0.1% (v/v and w/v, respectively). Cinnamaldehyde, cinnamon bark oil, clove bud oil, eugenol, and thyme oil were moderately inhibitive (MICs = 0.2% v/v), while cinnamic acid required a concentration of 0.5% (w/v). AIT was not effective with MICs in excess of concentrations tested (0.75% v/v). The bactericidal capability of the oil components carvacrol, cinnamaldehyde, eugenol, and thymol were further examined against Pediococcus acidilactici, Lactobacillus buchneri, and Leuconostoc citrovorum. Thymol at 0.1% (w/v) was bactericidal against L. citrovorum (>4‐log reduction), but resulted in a 2‐log CFU/mL reduction against L. buchneri and P. acidilactici. Cinnamaldehyde at 0.2% to 0.25% (v/v) was effective against L. citrovorum, L. buchneri, and P. acidilactici, resulting in a >2‐log reduction. All 3 organisms were susceptible to 0.2% carvacrol with >3‐log reduction observed after exposure for 6 h. Eugenol was the least effective. Concentrations of 0.2% and 0.25% (v/v) were needed to achieve an initial reduction in population, >3‐log CFU/mL after 6 h exposure. However, at 0.2%, P. acidilactici and L. buchneri recovered to initial populations in 48 to 72 h. Results indicate essential oils have the capacity to inactivate LAB that are commonly associated with spoilage of shelf stable low‐acid foods.     

能力验证乳粉中乳酸菌计数不确定度的评定

目的对能力验证乳粉样品中乳酸菌计数进行不确定度评定。方法依据能力验证作业指导书和GB4789.35-2010《食品安全国家标准食品微生物学检验乳酸菌检验》进行测定,再根据JJF 1059.1-2012《测量不确定度评定与表示》对不确定度来源进行分析和评定。结果乳酸菌计数过程中,分散性对结果不确定贡献较大,因此测定结果的不确定度采用检测结果的分散性进行评定。6份样品乳酸菌计数结果扩展不确定度为分别为0.02012、0.04337、0.01992、0.03296、0.02182和0.031379(P=95%,k=2.09)。结论此方法适用于类似检测条件下乳酸菌计数不确定度的评定。