屎肠球菌JT1701对人体肠系细菌的调控作用

用屎肠球菌JT1701与人体肠系有害菌（大肠杆菌、产气荚膜梭菌、脆弱拟杆菌）和人体肠系益生菌（婴儿双歧杆菌、嗜酸乳杆菌）分别及共同培养发现,肠球球菌对这些菌均有抑制作用。它能抑制这些菌氨的产生,降低培养基的pH。其原因是,屎肠球菌与氨产生相关的尿酶、氨基酸脱氨酶的种类少,酶活性亦低,而与NH4^ 同化相关的谷氨酸脱氢酶、谷氨酸合酶、谷酰氨合成酶的活性要高得多。表明屎肠球菌对人体肠系菌群具有调控作用。     

乳酸菌表达质粒的构建

粪肠球菌是乳酸菌的一个属．采用生物信息学方法,预测了粪肠球菌AS1．2984基因组中乳酸脱氢酶和三磷酸甘油醛脱氢酶的组成型启动子序列．设计引物通过PCR扩增得到这2段启动子序列,并克隆到乳酸菌一大肠杆菌穿梭质粒pNZ8037上,在启动子下游接上绿色荧光蛋白基因作为标记,构建乳酸菌的组成型蛋白表达质粒．通过电转化将上述改造过的pNZ8037质粒导入粪肠球菌中,在共聚焦显微镜中可以观察到绿色荧光蛋白的表达．在乳酸菌MRS培养基中加入乳酸、盐酸、氢氧化钠等试剂,发现可以调节绿色荧光蛋白的表达量．     

The 2.4-A crystal structure of the penicillin-resistant penicillin-binding protein PBP5fm from Enterococcus faecium in complex with benzylpenicillin

Penicillin-binding proteins (PBPs) are membrane proteins involved in the final stages of peptidoglycan synthesis and represent the targets of beta-lactam antibiotics. Enterococci are naturally resistant to these antibiotics because they produce a PBP, named PBP5fm in Enterococcus faecium, with low-level affinity for beta-lactams. We report here the crystal structure of the acyl-enzyme complex of PBP5fm with benzylpenicillin at a resolution of 2.4 A. A characteristic of the active site, which distinguishes PBP5fm from other PBPs of known structure, is the topology of the loop 451-465 defining the left edge of the cavity. The residue Arg464, involved in a salt bridge with the residue Asp481, confers a greater rigidity to the PBP5fm active site. In addition, the presence of the Val465 residue, which points into the active site, reducing its accessibility, could account for the low affinity of PBP5fm for beta-lactam. This loop is common to PBPs of low affinity, such as PBP2a from Staphylococcus aureus and PBP3 from Bacillus subtilis. Moreover, the insertion of a serine after residue 466 in the most resistant strains underlines even more the determining role of this loop in the recognition of the substrates.     

An alternative magnesium-based root canal disinfectant: Preliminary study of its effi cacy against Enterococcus faecalis and Candida albicans in vitro

Organisms invading root canal systems result in serious pulpal and periapical disease. To eliminate microorganisms and restrain secondary infections, dental materials with antibacterial properties are urgently needed in endodontics. Magnesium is considered as a promising biodegradable and biocompatible implant material. However, there are barely researches about its application in endodontic therapy. This work investigated the in vitro efficacy of magnesium powder against Enterococcus faecalis and Candida albicans compared with a common disinfectant, calcium hydroxide. With Calcium hydroxide served as a comparison it demonstrated the qualified antibacterial and anti-fungus properties of Mg as root canal disinfectant due to its high alkalinity of degradation, and the antimicrobial efficacy enhanced with the decreasing powder size.     

介质粒径、形状和生物膜对粪肠球菌在饱和活性炭柱中迁移的影响

通过室内柱实验,研究了介质粒径、介质形状和生物膜对粪肠球菌在饱和活性炭柱内的迁移的影响。结果表明:介质粒径、形状和和生物膜对粪肠球菌在饱和活性炭介质中的沉积与迁移有着重要影响。活性炭介质粒径越小,粪肠球菌在活性炭滤柱中的沉积量越多,流失率越小,在介质粒径为0.8 mm时,出现表面封阻现象;颗粒活性炭比同粒径的柱状活性炭更利于粪肠球菌的沉积;颗粒活性炭表面附着生物膜时,有利于提高粪肠球菌在饱和活性炭内的沉积量,减小其流失率。     

一株乳酸菌产类细菌素Enteriocin LK-S1的初步研究

从鸡肠道分离的 5 9株乳酸菌中 ,筛选出一株产类细菌素的乳酸菌 ,编号为SE - 81.初步鉴定为肠球菌属 (Enterococcus) .在排除有机酸和过氧化氢的干扰作用后 ,SE - 81菌株对溶壁微球菌(Micrococcuslysodeikticus)、金黄色葡萄球菌 (Staphylococcusaureus)和枯草杆菌 (Bacillussubtilis)等革兰氏阳性菌和大肠杆菌 (Escherichiacoli)及鼠伤寒沙门氏菌 (Salmonellatyphimurium)等革兰氏阴性菌有强烈的抑制作用 .用胰蛋白酶处理发酵上清液后 ,抑菌活性丧失 .因此初步认为该菌株产生一类具有广谱抑菌活性的类细菌素物质 ,命名为EnteriocinLK -S1.它具有较广的抗菌谱 ,作用pH在 4 .0～ 6 .0 ,有很好的热稳定性 .     

动物源性肠球菌的研究进展

综述了动物源性肠球菌的生物学特性，致病性，流行病学，实验室诊断和耐药性的研究进展。     

68株临床分离肠球菌的耐药性检测及临床意义

目的：了解肠球菌在临床标本中的分布及对常用的抗菌药物的耐药现状，指导临床合理用药．方法：对临床标本中分离出的细菌进行系统检验，采用纸片法对分离鉴定后的肠球菌进行药物敏感性试验．结果：肠球菌可在临床常见的多种标本中检出，粪肠球菌（86．7％）明显多于屎肠球菌（10．3％），其他肠球菌（3％）少见．对常用抗菌药物的耐药性，粪肠球菌和屎肠球菌之间的差异无统计学意义．结论：临床医生应关注临床常见病原菌的耐药性研究，参考抗菌药物敏感性试验结果调整用药种类．     

肠球菌研究进展

肠球菌是人类和动物肠道正常菌群的重要成员。由于抗生素的广泛使用,使肠球菌的感染不断上升,成为医院内感染的主要致病菌。由于肠球菌携带多种毒力因子和具有多重耐药性、天然耐药性以及获得性耐药等特性,给临床肠球菌感染的治疗和控制带来了极大的困难。文章就肠球菌生物学特性、分类地位、致病机制、耐药性、实验室诊断以及治疗等方面进行阐述。     

屎肠球菌hyl基因突变株的构建

目的：构建屎肠球菌类透明质酸酶（hyaluronidase,hyl）基因突变株,研究hyl基因的功能。方法：用pETX4577质粒构建屎肠球菌hyl基因重组自杀质粒,通过体内同源重组,筛选获得hyl基因的突变株,体外研究hyl基因缺失对突变株生长能力的影响。结果：经同源重组,利用卡那霉素抗性筛选,PCR、脉冲场电泳和southern blot进行鉴定获得基因突变株＊hyl。突变株在体外的生长能力低于野生株。结论：hyl基因突变株构建成功,hyl基因在生长中起着重要的作用,可能是屎肠球菌的毒力因子之一。