无乳链球菌的研究进展

无乳链球菌亦称B群链球菌（Group B streptococcus,GBS）,一直是新生儿和女性生殖道受感染的重要病菌,尤其是新生儿时期的感染是危及生命的重要原因,其病发症包括败血症、肺炎和脑膜炎等。在成年妇女的阴道和直肠内有15％～40％可以检出无乳链球菌,因此,这类女性所分娩的新生儿感染该菌的机率会比较高。     

无乳链球菌表面蛋白的研究进展

无乳链球菌是链球菌属的一个种,按Lancefild血清学分类,划归为B群(B群链球菌)。上世纪90年代以来,无乳链球菌是新生儿严重感染性疾病致病菌之一,在发达国家的感染率是围生儿间接死因的首位。由于该菌是许多妇女阴道的常驻菌群,在阴道和宫颈的定植率也很高,是引起新生儿侵袭性感     

100种中草药对无乳链球菌和海豚链球菌体外抑杀研究

无乳链球菌(Streptococcus agalactiae)和海豚链球菌(Streptococcus iniae)给罗非鱼(Oreochromis sp.)养殖带来了严重的经济损失, 而抗生素等药物的使用会造成细菌的耐药性和环境污染, 因此, 研究了100种中草药对罗非鱼链球菌体外抑杀效果, 以筛选出替代抗生素的绿色中草药。其中16种中草药具有较好的抑菌作用, 但将其pH 值调至7.0±0.04后, 大部分中草药的抑菌效果会显著下降(P<0.01), 只有桑白皮(Morus alba)、藿香(Agastache rugosa)、豨莶草(Siegesbeckia orientalis)、槐角(Sophora japonica)的抑菌效果比较明显。将pH 值调至7.0±0.04后, 采用二倍梯度稀释法测定这4种中草药的最低抑菌浓度(Minimal Inhibitory Concentration, MIC)和最小杀菌浓度(Minimal Bactericidal Concentration, MBC), 结果显示, 桑白皮抑杀无乳链球菌的效果最好, MIC和MBC均为0.3906 mg·mL-1; 豨莶草抑杀无乳链球菌的效果次之, MIC为0.3906 mg·mL-1, MBC为0.7813 mg·mL-1; 藿香、豨莶草、槐角抑杀海豚链球菌的效果最好, MIC和MBC均为0.3906 mg·mL-1。     

无乳链球菌耐药性及分子分型方法的研究进展

无乳链球菌(Streptococcus agalactiae)是链球菌属最主要的致病菌之一,又被称为B群链球菌(group B Streptococcus,GBS)。S. agalactiae致病性主要由毒力因子和表面蛋白引起,毒力因子包括荚膜多糖、溶血素、菌毛岛屿、透明质酸酶、磷酸甘油激酶和CAMP因子,表面蛋白是αC蛋白、表面免疫相关蛋白、黏附蛋白、纤维蛋白原结合蛋白、层黏连蛋白结合蛋白和纤溶酶受体蛋白。近8年的S. agalactiae耐药情况统计数据发现,S.agalactiae已对19种抗菌抗药物产生耐药,检出20个耐药基因和12种毒力因子。国内外S. agalactiae分子分型方法主要致力于血清型、多位点序列、脉冲场凝胶电泳、菌毛岛屿和细菌前噬菌体基因分型。本文阐述了S.agalactiae生物学特性、流行性致病信息、耐药性研究现状和分子分型方法研究进展,以期为进一步探明S.agalactiae耐药机制、开发治疗S. agalactiae的新型药物提供参考。     

酿脓链球菌Cas9核酸酶的重组表达、分离纯化及酶学特性

【背景】Cas9核酸酶是一种RNA引导的核酸内切酶,可与单链向导RNA (single-guide RNA,sgRNA)形成稳定的核糖核蛋白复合物,识别和切割特定的核苷酸片段。由于其具备高灵活性和高效率的特点,目前已经成为基础科学研究领域和临床治疗方法中使用最广泛的基因编辑工具。【目的】为Cas9核酸酶的合理开发和利用提供理论依据。【方法】利用大肠杆菌表达系统表达野生型酿脓链球菌(Streptococcus pyogenes) Cas9核酸酶,经硫酸铵沉淀和镍柱亲和层析两步纯化获得较高纯度表达产物,并对其热稳定性、pH稳定性、金属离子的影响等酶学特性进行研究。【结果】经高密度发酵后,大肠杆菌湿菌重达191.0 g/L。纯化后酿脓链球菌Cas9核酸酶的比酶活达641.29 U/mg,纯化倍数为16.02,收率为46.40%。Cas9核酸酶在25-42°C保温2 h后剩余酶活保持在65%以上,而在45°C保温15 min后全部失活;其在pH 6.0-10.0范围内稳定性较高,剩余酶活大于68%,在pH9.0时稳定性最高;0.5-20.0mmol/L浓度范围内的Mg²⁺...     

牛源无乳链球菌长尾噬菌体的特性

【目的】分离鉴定噬菌体,对其生物学特性进行研究,并筛选候选毒株为防控牛源无乳链球菌的感染提供依据。【方法】分别采用从牛奶或环境中分离、溶原菌诱导两种方法分离鉴定无乳链球菌噬菌体,利用双层琼脂平板法纯化。将新分离鉴定毒株与前期已分离鉴定的源自乳腺炎牛奶的无乳链球菌噬菌体JX01进行分析和比较,包括噬菌体透射电镜形态观察、对55株无乳链球菌和其他细菌的宿主谱鉴定、噬菌体基因Eco R I、Sal I、Xba I或Pst I的酶切图谱、最适MOI、吸附曲线和一步生长曲线、不同保存条件下的稳定性等。【结果】分离鉴定的3株噬菌体LYGO9、HZ04和p A11(诱导自牛源菌株HAJL2011070601)与JX01比对分析,结果显示,4株噬菌体均为长尾噬菌体;Eco R I、Sal I、Xba I、Pst I的酶切图谱分获4、3、3或2种带型,显示4株噬菌体为不同毒株;均特异性裂解牛源无乳链球菌,对42株牛源无乳链球菌的裂解率如下:LYGO9为28.6%(12/42)、p A11为31%(13/42)、HZ04为47.6%(20/42)、JX01为54.8%(23/42);同时,LYGO9与p A11、HZ04和JX01分别有共同宿主11、12和11株;HZ04与JX01有共同宿主18株,提示它们具有同源性。LYGO9感染宿主的潜伏期短,仅5 min,平均裂解量为30。分离株在SM液中4°C至少可保存1个月。【结论】分离鉴定的3株牛源无乳链球菌噬菌体均为长尾噬菌体,其中LYGO9潜伏期短、裂解量较大。     

具有拮抗无乳链球菌能力乳杆菌的筛选及抑菌特性

目的 从罗非鱼(Nile tilapia)肠道中筛选出具有抑菌作用的乳杆菌,测定其对无乳链球菌(Streptococcus agalactiae)的抑菌效果,分析乳杆菌抑制无乳链球菌的有效成分,并利用分子生物学手段对筛选的乳杆菌菌种进行鉴定。 方法 采用双层平板法对具有抑制无乳链球菌的乳杆菌进行筛选,牛津杯法对抑菌效果进行测定,酶蛋白敏感性测定、热处理、有机酸处理等方法分析抑菌活性物质有效成分,16S rDNA分子标记对乳杆菌进行鉴定。 结果 从罗非鱼肠道中筛选出14株乳杆菌,其中菌株RS2对无乳链球菌具有明显的抑菌效果;不同蛋白酶种类、pH处理对乳杆菌无细胞培养液均有不同的影响,经80 ℃处理的乳杆菌无细胞培养液,其抑菌效果未显著改变(t=0.169 2,P=0.873 8)。此外,此株乳杆菌对猪霍乱沙门菌(Salmonella choleraesuis)、大肠埃希菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和志贺菌(Shigella sp.)等病原菌具有良好的抑制作用。经鉴定,该乳杆菌为植物乳杆菌(Lactobacillus plantarum)。 结论 从罗非鱼肠道中分离得到的植物乳杆菌菌株RS2对无乳链球菌等致病菌具有一定的抑制作用,推断其抑菌有效成分为细菌素类物质。此项研究对开发抗生素替代产品,提高食品的品质具有一定价值。     

围产期无乳链球菌携带状况及耐药性分析

目的 探讨新疆乌鲁木齐市围产期无乳链球菌携带状况及耐药性,为临床合理使用抗菌药物提供依据。方法 回顾性分析2014年1月—2016年11月围产期6 003例泌尿生殖道分泌物标本,采用法国梅里埃Vitek 2 Compact全自动细菌鉴定和药敏系统检测,从中检出151株无乳链球菌,分析药敏、查阅其病历基本信息、新生儿出生状况等。结果 6 003例围产期泌尿生殖道标本中检出151株无乳链球菌,检出率为2.52%,其中≤35岁、>35岁孕产妇中无乳链球菌感染率分别为2.55%、2.26%,两者相比差异无统计学意义（P>0.05）;民族中,汉族、维吾尔族、回族、哈萨克族中无乳链球菌感染率分别为2.70%、2.63%、2.18%、1.73%,相比差异无统计学意义（P>0.05）;>37周感染无乳链球菌101例且诊断胎膜早破有76例;孕1次感染无乳链球菌有90例,孕3次感染无乳链球菌有33例,且有20例曾有流产史;新生儿宫内感染中有1例感染无乳链球菌属于早发型。药敏结果中,无乳链球菌对氨苄西林、青霉素G敏感率分别为97.97%、98.63%;对红霉素、四环素、克林霉素和左氧氟沙星耐药率较高,分别为77.46%、72.85%、58.94%和54.30%。结论 临床应重视在围产期对无乳链球菌的检测和耐药情况,合理使用抗生素,可有效地预防和治疗该菌的感染。     

围产期孕妇泌尿生殖道无乳链球菌耐药性分析及临床意义

目的 了解围产期孕妇泌尿生殖道无乳链球菌感染及耐药分布为临床合理用药提供依据,并提出预防措施,以引起临床重视.方法 对门诊、住院围产期孕妇送检的泌尿生殖道标本进行培养鉴定,并对分离的无乳链球菌进行药敏试验,并用WHONET 5.5软件分析.结果 260株无乳链球菌药敏结果显示,对万古霉素、利奈唑胺、青霉素和头孢曲松的耐药率最低,对红霉素、克林霉素、左氧氟沙星的耐药率较高,分别为61.5％、57％和49.3％.结论 临床医生应重视对围产期孕妇无乳链球菌的检测,实验室应准确报告无乳链球菌药敏结果,对临床合理用药治疗无乳链球菌感染具有重要指导意义并可预防其危害性.     

A note on bile tolerance in Streptococcus agalactiae

Streptococcus agalactiae strains isolated from humans were found to be able to grow in the presence of high levels of bile but not in media containing levels of bile salts or surfactants commonly considered equivalent to bile in selective media.     

Prevalence of IgA receptors in clinical isolates of Streptococcus pyogenes and Streptococcus agalactiae; Serologic distinction between the receptors by blocking antibodies

Abstract Group A and B streptococci ( Streptococcus pyogenes and Streptococcus agalactiae ) are the only known bacterial pathogens expressing IgA Fc-receptors. However, the IgA binding proteins of the two species have been found genetically unrelated. In the present investigation the binding of human IgA among clinical isolates of group A and group B streptococci was studied and the respective IgA-binding epitopes were compared serologically. Surface binding of radiolabelled, monoclonal human IgA1 occurred in 38% of 115 unselected group A streptococcal isolates. Comparing four predominant T-types, IgA-binding was found in 77% and 85%, respectively, of types T4 and T28 strains but only in 5% and 25%, respectively, of T1 and T12 strains. In group B streptococci, 70% of 58 type Ib strains but only 2% of 399 strains of other serotypes bound IgA. Using rabbit immune sera raised to the two streptococcal species it was found that strains exhibiting IgA Fc-receptors often induced antibodies blocking the binding of IgA to bacteria. Furthermore, the blocking shown by an individual serum was restricted to the streptococcal group used for immunization showing that also the IgA-binding epitopes in group A and B streptococci are conformationally distinct. Though infections with serotypes often binding IgA, compared to other types, are not known to differ, it is assumed that the non-immune binding of IgA might favour mucosal colonization of the organisms.     

食品中金黄色葡萄球菌肠毒素的快速检测方法

采用反向被动乳胶凝集法 (RPLA)和mini VIDAS (ELFA)两种方法对 42份金黄色葡萄球菌阳性样品进行了肠毒素检测。结果RPLA法的金葡菌肠毒素检出率为 61.9% (P<0.05 )要高于ELFA法的检出率 50.0% (P <0.05 ) ,但检测时间长 ( 20h)。在实验中我们还发现 ,血浆凝固酶阴性的葡萄球菌也可产生肠毒素 ,其原因有待进一步的研究。     

Stabilization and polysaccharide storage in group A Streptococcus pyogenes

Water-shock treatment of group A Streptococcus pyogenes released a mixture of nucleotide-like substances and small amounts of protein. The amount of protein was much less than found with osmotic shock of Gram-negative bacteria. In group A S. pyogenes the osmolytes released exhibited as much as a 6-fold change in respect to different growth phases. Osmolyte release was dependent on the stabilization agent used and independent of cellular metabolic activity. The released osmolytes were found to be required for optimal intracellular iodophilic polysaccharide (IPS) storage. Stabilization of washing solutions, and IPS storage medium with metabolically inert non-ionic organic compounds prevented osmolyte loss and enhanced IPS storage. Polyvinyl pyrrolidone and polyethyleneglycol (MW greater than 1000) exhibited the same protective effects as found with calf serum. Smaller non-ionic organic compounds provided similar protective action but the bacteria were more susceptible to osmotic stress.     

A selective-differential medium for detection of Streptococcus agalactiae

A practical culture medium which allows direct plating of milk samples for detection and differentiation of Streptococcus agalactiae within 48 hours is described. Most other micro-organisms likely to be present in these samples are inhibited. Although some strains of Staphylococcus species and ofStreptococcus faecalis are able to grow, they may be differentiated on the basis of reaction in the medium surrounding the colonies.     

Rapid, Direct Fluorescent-Antibody Method for the Detection of Salmonellae in Food and Feeds

An improved immunofluorescent-antibody (FA) method for the detection of salmonellae in foods and feeds was developed. This FA method combines a rapid cultural phase and a serological phase that allow for propagation of salmonellae in a minimum time, employing the industrial 8-hr work day as a guide. Two hundred fifty naturally contaminated human food and animal feed samples, representing 647 trials, were tested by the FA method. A total of 18 different food and feed samples was used. The method used by the Association of Official Analytical Chemists (AOAC) for the detection of salmonellae was the control method. The percent agreement when comparing the FA slide method to the AOAC method ranged from 87.1 to 95.3%, depending upon the conjugated antisera used in comparative studies.     

Effect of Streptococcus pyogenes on Tissue Cells

Human tissue cell lines from each of the three primary germinal sources, ectoderm (conjunctiva and carcinoma of the buccal mucosa), entoderm (intestine and liver), and mesoderm (heart and monocytes) were inoculated with group A Streptococcus pyogenes, Staphylococcus aureus, and group D streptococci and were then observed. In addition, the effect of these bacteria on mouse fibroblasts was studied. All of the cell lines appeared to be equally susceptible to damage, but damage to the cells by S. pyogenes occurred only when living, actively multiplying bacteria were in contact with the tissue cells. Streptococcal products in the form of "used" growth medium had no observable effect on the cells. Cytopathogenic effects were first noticed about the time one would expect the bacteria to have reached the end of the log phase of growth. No damage to the tissue cells was noted when group A streptococci were separated from the cells by membrane filter diffusion chambers or dialyzing membranes, but a membrane did not protect cells from deleterious effects of staphylococci or group D streptococci. Group A streptococci survived in the tissue culture medium, but multiplication did not occur unless living tissue cells were present.