我国食源性蜡样芽孢杆菌毒力基因和药物敏感性研究

目的 了解我国不同地区食源性蜡样芽孢杆菌的毒力基因携带特点及其对抗生素的敏感性,为食源性食物中毒的防治提供参考依据.方法 采用PCR方法对2011年我国不同地区收集的238株食源性蜡样芽孢杆菌10种毒力基因进行检测;采用微量肉汤稀释法测定其抗生素敏感性.结果 溶血素BL基因、肠毒素T基因和细孢毒素K基因是我国食源性蜡样芽孢杆菌的主要毒力基因,至少携带一个毒力基因的菌株达到检出菌总数的87.4％;蜡样芽孢杆菌对庆大霉素、万古霉素、环丙沙星、复方新诺明的敏感率为100％,对红霉素、四环素、氯霉素、克林霉素的敏感率分别为88.8％、90.2％、99.6％、87.1％,对氨苄西林和头孢噻肟的敏感率仅为0.4％和5.4％.结论 我国食源性蜡样芽孢杆菌毒力基因携带率较高,对食品安全和公共健康构成潜在的威胁;蜡样芽孢杆菌对氨苄西林、头孢噻肟的敏感性差,不应作为经验用药和预防用药.     

Bacillus cereus adhesion: an investigation of the physicochemical characteristics of surface and effect of bio adhesion on the properties of silicone

The initial microorganism adhesion on substrate is an important step for biofilm formation. The surface properties of the silicone and Bacillus cereus were characterized by the sessile drop technique. Moreover, the physicochemical properties (hydrophobicity; electron donor/electron acceptor) of surface adhesion and the impact of bio adhesion on the silicone were determined at different time of contact (3, 7, and 24?h). The results showed that the strain was hydrophilic (Giwi?=?3.37?mJ/m²), whereas the silicone has hydrophobic character (Giwi?=??68.28?mJ/m²). Silicone surface presents a weak electron-donor character (γ ^??=?2.2?mJ/m²) conversely to B. cereus that presents an important electron donor-parameter (γ ^??=?31.6?mJ/m²). The adhesion of B. cereus to silicone was investigated using environmental scanning electron microscope and image analysis was assessed with the Matlab^® program. After 3?h of contact, the data analysis, confirmed the bio adhesion with an amount of 9.610⁵?cfu/cm² adhered cells. After 24?h, the percentage of silicone covered reached 93%. Furthermore, despite the difference in hydrophohbicity, the interaction between B. cereus and substrata was favoured by the thermodynamic model of adhesion (ΔG _adhesion ?<?0). The real time investigation of the effect of B. cereus adhesion on the physicochemical properties of silicone has revealed that the substrata becomes hydrophilic (θ°?=?47.3, ΔGiwi?=?23.7?mJ/m²), after 7?h of contact. This bio adhesion had also favoured the increase of electron donor/acceptor character of silicone (γ ^??=?53.1?mJ/m² and γ ⁺?=?5.3?mJ/m²).     

苎麻脱胶用菌株S2的酶液稳定性

对S2所产酶液的活性中心及其在不同环境、温度和pH值等条件下的稳定性进行分析。结果表明:不同金属离子对S2酶液活性的影响不同,Ca2+、Co2+对S2所产酶液具有显著促进作用,有利于酶液脱胶处理,而Cu2+、Zn2+等重金属离子对S2所产的酶液的活性具有比较强烈的抑制效应;酶活性在不同pH值、不同温度下的稳定性是不相同的,且不同条件下的稳定性差异很大,当pH值为8.5、最适温度为55℃时,S2酶活的稳定性比较高。     

原料乳中蜡样芽孢杆菌部分致病基因的鉴定及毒力评价

研究原料乳中蜡样芽孢杆菌的潜在威胁,对我国10 个省市原料乳中蜡样芽孢杆菌的污染状况进行调查,并利用PCR 扩增技术及血平板检测的方法分析乳源性蜡样芽孢杆菌中的毒性分布。结果表明,原料乳中蜡样芽孢杆菌检出率为33%,检出水平为1 × 103～1 × 106 CFU/ml,检出的蜡样芽孢杆菌中25 株(75.8%)能产生溶血素BL,24 株(72.7%)含有bceT 基因,至少产生一种毒素的菌株有31 株占检出菌总数的93.9%。研究结果证实我国原料乳中的蜡样芽孢杆菌污染状况不容乐观,严格监控原料乳中的蜡样芽孢杆菌污染,对生产出优质乳制品具有重要意义。     

一株具有降解污水中COD和氨氮能力的微生物研究

以某酒厂污水处理站的活性污泥为原材料,使用微生物筛选和培养技术筛选出若干株微生物,其中编号为WS-16的菌株具有降解氨氮、化学需氧量(COD)生理活性,采用不同接种量和培养时间进行WS-16降解氨氮和COD研究;并对WS-16进行微生物测序.结果 证明:不同培养时间菌株WS-16降解污水中COD和氨氮更明显,氨氮从37...     

Recipes for antimicrobial wine marinades against Bacillus cereus, Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella enterica

ABSTRACT:  We have evaluated bactericidal activities against Bacillus cereus , Escherichia coli O157:H7, Listeria monocytogenes , and Salmonella enterica of several antimicrobial wine recipes, each consisting of red or white wine extracts of oregano leaves with added garlic juice and oregano oil. Dose-response plots were used to determine the percentage of the recipes that resulted in a 50% decrease in colony-forming units (CFU) at 60 min (BA₅₀). Studies designed to optimize antibacterial activities of the recipes demonstrated that several combinations of the naturally occurring plant-derived ingredients rapidly inactivated the above mentioned 4 foodborne pathogens. We also showed that (a) incubation temperature affected activities in the following order: 37 °C > 21 °C > 4 °C; (b) varying the initial bacterial concentrations from 10³ to 10⁴ to 10⁵ CFU/well did not significantly affect BA₅₀ values; (c) storage of 3 marinades up to 2 mo did not change their effectiveness against Salmonella enterica ; and (d) polyphenolic compounds isolated by chromatography from red wine exhibited exceptional activity at nanogram levels against 2 strains of Bacillus cereus . These observations suggest that antimicrobial wine formulations have the potential to improve the microbiological safety of foods.     

海洋氨肽酶菌株的筛选鉴定及其酶学特性研究

从大连渤海海域海泥海水样品中分离出一株高产海洋氨肽酶(aminopeptidase)菌株YZ1-2,对其进行形态学、生理生化、分子生物学(16S rDNA)鉴定,确定该菌株为蜡样芽孢杆菌(Bacillus cereus)。并对其产海洋氨肽酶进行酶学特性研究,结果表明,最适作用温度为30 ℃;最适作用pH值为8.5;Co2+、Zn2+等能较强地激活氨肽酶的活性,Ni2+、Ca2+等对酶的抑制性较强;乙二胺四乙酸(EDTA)可以有效地抑制氨肽酶活性。     

产角蛋白酶植物内生菌的筛选与鉴定

以不同植物的内生菌为出发菌株进行产角蛋白酶菌株的筛选,通过脱脂牛奶平板、高压蒸煮后的羽毛摇瓶实验及未经处理鸡毛摇瓶实验筛选到一株能够在48h内降解未经高压蒸煮的鸡毛的内生菌,该菌株来源于樟树叶片。通过形态学观察、生理生化实验结合16S rDNA基因序列分析的方法确定该菌株为蜡样芽孢杆菌,命名为Bacillus cereus Z-3。以不同的角蛋白为底物进行发酵培养,酶活力测定结果显示该酶降解角蛋白能力由强到弱的顺序为鸡毛、羊毛、头发。     

Extended shelf life milk processing: Effect of simulated cleaning in place on the germination and attachment of Bacillus cereus spores

The effect of simulated cleaning in place (CIP) was determined on the structure, attachment and growth of Bacillus cereus spores isolated from raw milk and biofilms in filler nozzles from extended shelf life (ESL) milk processing lines. Simulated CIP treatment structurally affected >98% of B. cereus spores, while 0.1% remained intact. Following simulated CIP treatment, B. cereus spores were able to attach to stainless steel coupons and form biofilms. B. cereus spores were capable of germination and growth under refrigerated conditions for more than 28 days. Contamination with B. cereus spores may lead to a reduced shelf life and potentially be a safety risk in ESL milk with a prolonged shelf life.     

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。