Plasminogen interaction and activation on Streptococcus mutans surface

A number of pathogenic microorganisms have been previously shown to bind plasminogen. The subsequent activation of plasminogen into plasmin can contribute to their virulence. In this study, we have shown that Streptococcus mutans is able to bind both human plasminogen and plasmin. Binding of plasminogen to S. mutans was inhibited by L-lysine and epsilon-aminocaproic acid, indicating that binding is mediated via lysine-binding sites of plasminogen. S. mutans enhanced the activation of plasminogen by tissue plasminogen activator but not by urokinase. This enhancement turned out to be dependent on cell concentration. Zymogram analysis showed that the plasmin activity acquired after plasminogen binding and activation is the most important proteolytic activity in the strain tested. These results suggest a mechanism involving acquisition of a host protease that might contribute to the infective process of this microorganism.     

某健齿露防龋功能性评价的实验研究

目的　评价某健齿露对龋齿的预防作用。方法　离体试验 :将一定浓度的样品加入变形链球菌培养管中 ,培养一定时间 ,经革兰氏阳性染色和分光光度计测量观察变形链球菌的生长情况 ,测定其百分粘附率 ,并用酸度计测定细菌产酸后pH值。动物试验 :采用变形链球菌建立大鼠龋损模型 ,设立空白对照组 ,低、中、高三个剂量组 ,每日给样 ,连续 4 0天后处理动物 ,观察各组大鼠磨牙患龋情况 ,参照keyes经典龋齿计分标准进行龋齿计分。结果　变形链球菌生长正常 ,但易形成长链 ,粘附率降低。pH值升高 ,大于 6。动物实验表明 :实验组与对照组龋损程度、龋齿计分之间差异有显著性 (P <0 0 1)。结论　该样品能减少龋损的形成 ,有效降低大鼠龋病的发生、发展 ,有一定的防龋功能。其防龋机理在于该样品可促进变形链球菌凝集 ,抑制变形链球菌在玻璃上的粘附 ,降低变形链球菌产酸。     

Current status of a mucosal vaccine against dental caries

The evidence of a specific bacterial cause of dental caries and of the function of the salivary glands as an effector site of the mucosal immune system has provided a scientific basis for the development of a vaccine against this highly prevalent and costly oral disease. Research efforts towards developing an effective and safe caries vaccine have been facilitated by progress in molecular biology, with the cloning and functional characterization of virulence factors from mutans streptococci, the principal causative agent of dental caries, and advancements in mucosal immunology, including the development of sophisticated antigen delivery systems and adjuvants that stimulate the induction of salivary immunoglobulin A antibody responses. Cell-surface fibrillar proteins, which mediate adherence to the salivary pellicle, and glucosyltransferase enzymes, which synthesize adhesive glucans and allow microbial accumulation, are virulence components of mutans streptococci, and primary candidates for a human caries vaccine. Infants, representing the primary target population for a caries vaccine, become mucosally immunocompetent and secrete salivary immunoglobulin A antibodies during the first weeks after birth, whereas mutans streptococci colonize the tooth surfaces at a discrete time period that extends around 26 months of life. Therefore, immunization when infants are about one year old may establish effective immunity against an ensuing colonization attempts by mutans streptococci. The present review critically evaluates recent progress in this field of dental research and attempts to stress the protective potential as well as limitations of caries immunization.     

变形链球菌表面蛋白真核表达质粒pcDNA3/pacA和pcDNA3/pacP在哺乳动物细胞中的表达

目的:研究变形链球菌表面蛋白真核表达质粒pcDNA3/pacA 及pcDNA3/pacP在哺乳动物细胞中的转录及表达情况。方法:利用脂质体介导的转染技术,将真核表达质粒pcDNA3/pacA 及pcDNA3/pacP分别转染COS-7细胞,1mg*ml-1 G418加压筛选获取稳定转染的COS-7细胞之后,采用RT-PCR法、LSAB法、流式细胞术及Western印迹法,对真核表达质粒中插入基因pac-A和pac-P的转录及表达产物进行检测。结果:真核表达质粒pcDNA3/pacA及pcDNA3/pacP的插入基因在导入哺乳动物细胞后具有转录和翻译活性,表达的蛋白质产物可位于胞内、胞膜及胞外。结论:构建的真核表达质粒pcDNA3/pacA 和pcDNA3/pacP能在哺乳动物细胞中表达插入基因所编码的蛋白质,为进一步的动物实验提供了实验依据。     

Prediction of caries activity in children with today''s low caries incidence

One hundred 14-yr-old children were observed over 1 yr to find out if caries incidence and caries progression could be predicted in a low prevalence child population by means of well-known caries related factors. The mean caries incidence was low (0.45, SD 0.70) but, on the other hand, 32% of the children developed at least one new lesion during the test period. In only eight out of 35 children progressing lesions were demonstrated. Independent variables at baseline examination were caries prevalence, sucrose intake, fluoride exposure, oral hygiene, saliva secretion rate, and salivary concentrations of mutans streptococci and lactobacilli. A weak but statistically significant correlation was demonstrated between caries incidence and caries prevalence. No other significant correlations were shown. It was concluded that caries activity could not be predicted in this population. Low disease prevalence was a major reason for the weak correlations.     

壳寡聚糖对变形链球菌黏附的影响

目的:研究壳寡聚糖对变形链球菌蔗糖依赖性黏附的影响。方法:使用不同浓度的壳寡聚糖与变形链球菌S.mutansATCC25175共同培养,计算壳寡聚糖对变形链球菌的黏附抑制率的影响,同时扫描电镜下观察变形链球菌在玻片的形态学特征。结果:变形链球菌对玻片的黏附率随培养基中壳寡聚糖浓度的升高而下降。扫描电镜图片显示壳寡聚糖组细菌间基质少,菌细胞清晰。而空白组细菌则包裹有较多的胶冻状基质。结论:壳寡聚糖可以有效抑制变形链球菌的蔗糖依赖性黏附。     

绿原酸防龋的实验研究

目的 研究绿原酸对龋病发生发展的抑制效果。方法 制备不同浓度绿原酸,采用液体稀释法检测其体外抑制变形链球菌和远缘链球菌的效果;建立SD大鼠人工龋模型,分别用绿原酸溶液、甲硝唑洗必泰溶液和蒸馏水给大鼠施药,采用Keyes记分法观察绿原酸对大鼠口腔内龋齿发生发展的抑制效果。结果 绿原酸溶液对变形链球菌ATCC10449株和远缘链球菌OMZ65株的最小抑菌浓度均为2.5 mg/mL,最小杀菌浓度分别为7.5 mg/mL和5 mg/mL。在人工龋大鼠模型中,与蒸馏水相比,绿原酸组龋齿计分明显降低,而与甲硝唑洗必泰组相近。结论 绿原酸对变形链球菌和远缘链球菌生长有明显抑制作用,并可有效抑制大鼠龋齿的发生。     

高龋及无龋儿童变形链球菌分离株的蔗糖粘附能力比较

目的:探讨高龋和无龋儿童变形链球菌(变链菌)临床分离株的蔗糖依赖性粘附能力。方法:选取本实验室从10例高龋儿童和10例无龋儿童(3￣5岁)牙菌斑内分离、鉴定所得的60株变链菌临床分离株进行研究。采用紫外分光光度计,检测来自高龋儿童(dmfs≥6)的39株和无龋儿童(dmfs=0)的21株变链菌在含糖培养基中对玻壁的粘附情况。采用SPSS12.0软件包进行单因素方差分析,比较高龋儿童和无龋儿童之间牙菌斑内变链菌分离株的玻壁粘附能力。结果:在含1%蔗糖的培养基中,高龋组变链菌分离株对玻壁的粘附比平均值为(55.49+26.16)%,无龋组变形链球菌分离株对玻壁的粘附比平均值为(27.01+18.39)%,2组间差异具有显著性,P<0.01。结论:在含蔗糖环境中,分离自高龋儿童牙菌斑的变链菌株对玻壁的粘附能力高于来自无龋儿童的变链菌分离株,提示变链菌临床分离株的粘附能力与其致龋力相关。     

基于唾液s.mutans、s.sobrinus定量值的儿童龋病Logistic预测模型研究

目的：为了进一步了解儿童乳牙龋病活性与口腔变形链球菌和乳酸杆菌（s.mutans、s.sobrinus）数更精确的量化关系,尝试建立新的可行的基于唾液s.mutans、s.sobrinus定量值的儿童龋病Logistic预测模型。方法：建立s.mutans、s.sobrinus的定量检测方法-FQ PCR法,对203名3～5岁儿童进行龋病调查,同时采用FQ PCR方法检测其口腔唾液s.mutans、s.sobrinus数量。6个月后回访检查,根据调查结果建立儿童龋病Logistic回归分析模型,对儿童龋病危险性进行评估分析。结果：3～5岁儿童患龋率和s.mutans、s.sobrinus检出率都随年龄的增加而上升;龋病组和龋活跃组唾液s.mutans、s.sobrinus检出率、数量明显高于健康组和龋不活跃组;本实验选择相关性最好的3个指标（唾液s.mutans、s.sobrinus计数对数值、龋失补牙面数）建立的儿童龋病Logistic回归模型的特异性为92.78%,灵敏性为81.52%,总体正确率达89.24%,显示了很好的预测效果。结论：基于FQ PCR构建的儿童龋病预测模型,预测准确率、特异性、灵敏性均优于其它预测模型,显示了较好的临床实用性。     

Serotype‐specific polysaccharide of Streptococcus mutans contributes to infectivity in endocarditis

Streptococcus mutans and other viridans streptococci have been implicated as major etiological agents of infective endocarditis. The serotype‐specific rhamnose‐glucose polysaccharide (RGP) of S. mutans has several biological functions that appear to be essential for the induction of infective endocarditis. The aim of this study was to examine the contribution of RGP to the infectivity of S. mutans in infective endocarditis using a rat model. The RGP‐defective mutant of S. mutans showed reduced ability to induce infective endocarditis compared to the parental strain. The ability of S. mutans to induce infective endocarditis was not consistent with the binding capacity of the organism to extracellular matrix proteins. The results suggest that S. mutans containing whole RGP is more virulent than the RGP‐defective mutant, and the RGP has an important role for the induction of infective endocarditis by S. mutans.