变链素研究进展

细菌素是由某些细菌产生的一种抗菌性多肽,变异链球菌产生的细菌素称变链素。目前已有多种变链素被分离纯化,并完成氨基酸序列和基因序列分析。本文介绍了细菌素的新概念和6种不同变链素的研究现状。     

变链素研究进展

细菌素是由某些细菌产生的一种抗菌性多肽，变异链球菌产生的细菌素称变链素。目前已有多种变链素被分离纯化，并完成氨基酸序列和基因序列分析。本文介绍了细菌素的新概念和6种不同变链素的研究现状。     

变形链球菌细菌素免疫蛋白作用及其与密度感应关系的研究进展

细菌素免疫蛋白是细菌为避免受到抗菌剂的影响和自身分泌抗菌多肽抑制所产生的保护性蛋白分子。变形链球菌产生的细菌素称为变链素,是一类具有抗菌活性的多肽。变形链球菌合成的细菌素免疫蛋白和变链素两者间产生协同作用,是细菌耐药性提高和抗药性出现的原因之一,使其能更好地在复杂的口腔环境中生存。本文就变形链球菌细菌素免疫蛋白的研究进展作一综述。     

密度感应相关性变链素及其作用分析

细菌素是由某些细菌在代谢过程中产生的一类具有抗菌活性的蛋白质或多肽,变异链球菌产生的细菌素称为变链素.变链素可能与口腔生物膜中变异链球菌的致龋性及其在牙面的定植有关.目前已有多种变链素被分离、纯化并完成了基因序列和氨基酸序列的测定,变链素与密度感应调控系统的关系及在新型抗菌制剂研发中的应用价值已受到人们关注.本文就密度...     

利用特异分子探针DNA分析证实变形链球菌细菌素的多态性

变形链球菌产生的细菌素(变链素)在龋病的发生、发展中扮演重要角色。按抑菌谱及交叉免疫反应不同,不同菌株变链素又可分为24个相似的亚群。通过蛋白纯化和氨基酸序列分析可鉴定一些细菌素,而DNA杂交可获得不同亚群初级结构的相似性。本研究旨在应用变链素的编码基因     

血链球菌细菌素对伴放线聚集杆菌和白色念珠菌生物膜作用的研究

目的:研究血链球菌细菌素分别对单独培养及混合培养的伴放线聚集杆菌(A.a)和白色念珠菌(C.a)生物膜的最小抑菌浓度(MIC)。利用激光共聚焦显微镜研究血链球菌细菌素对A.a及混合培养的A.a和C.a生物膜活性的影响。方法:通过低温高速离心,细胞破碎,盐析等方法提取血链球细菌素—血链素。采用二倍稀释法,测定血链素对单独和混合培养的A.a及C.a的MIC;血链素作用于A.a及混合培养的A.a和C.a后,利用激光共聚焦显微镜分别在2 h、6 h、12 h、24 h、48 h、72 h观察生物膜活性的变化。结果:血链素对单独培养的A.a的MIC为0.25 g/L;血链素对单独培养的C.a的MIC为0.125 g/L;血链素对混合培养的A.a及C.a的MIC为0.5 g/L。通过激光共聚焦显微镜观察,血链素对A.a生物膜活性有较强的抑制作用,最显著的时间在72 h;血链素对混合培养的A.a及C.a生物膜活性同样具有较强的抑制作用,最显著的时间在48 h。结论:血链素对A.a及混合培养的A.a及C.a生物膜活性均有抑制作用。     

血链球菌细菌素对牙龈卟啉单胞菌生长曲线及细胞内钙离子浓度的影响

目的：研究血链球菌细菌素对牙龈卟啉单胞菌（Porphyromonas gingivalis P．g）生长曲线的影响。探讨血链球菌细菌素对牙龈卟啉单胞菌细胞内钙离子浓度的影响。方法：通过低温高速离心，超声破碎等方法提取血链素，使血链素作用P．g，于37℃厌氧培养：采用微量液体对倍稀释法测定血链素对P．g的最小抑菌浓度（MIC）。选用不同浓度的血链素作用P．g，分别于0、4、8、12、16、20、24、48h时测定各组细菌悬液在590nm波长处的A值，并绘制生长曲线。用Fluo-3／AM负载P．g细胞内钙离子，在激光共聚焦显微镜下观察Ca抖荧光强度变化。结果：血链素对P．g有显著抑制作用，其MIC为0．0625g／L。血链素作用后，P．g的生长曲线在8～16h发生显著改变，对数生长期被延迟了8h。血链素作用后，P．g细胞内钙离子浓度显著降低，与对照组相比差异具有统计学意义（P〈0．01）。结论：血链球菌细菌素对牙龈卟啉单胞菌有明显的抑制作用，在本实验范围内，随着血链素浓度的升高其抑制作用逐渐增强。血链球菌细菌素可导致牙龈卟啉单胞菌细胞膜钙离子通透性增强。     

细菌黏附的研究进展

龋病的发生是以致龋菌附着于牙面、集聚、菌斑形成,最后定居于牙面为先决条件的.没有细菌的黏附就不可能有牙面生态膜的形成,也就没有龋病的发生.本文就细菌的黏附现象、黏附机制及对黏附过程产生影响的因素等方面研究进展作一综述.     

血链球菌细菌素对白色念珠菌及热带念珠菌菌体形态影响的研究

目的:研究血链球菌细菌素对白色念珠菌(C.a)及热带念珠菌(C.t)的抑制作用及形态学影响。方法:通过低温高速离心,超声破碎等方法提取血链素,使血链素分别作用于单独及混合培养的C.a及C.t,于37℃下80r/min振荡培养。培养12h时,以平板菌落计数法测定不同浓度血链素的抑菌活性;每2h测1次各组菌悬液的A值,并绘制生长曲线,观察血链素对C.a及C.t生长曲线的影响。在血链素对C.a及C.t的作用过程中,利用光学显微镜及扫描电镜对菌体形态进行观察。结果:单独及混合培养的C.a及C.t在1g/L血链素作用后菌落数低于对照组,差异有统计学意义(P<0.05)。血链素作用后,C.a及C.t的生长曲线在6～14h发生显著改变,对数生长期被推迟8h。血链素作用后,C.a及C.t的孢子及菌丝表面出现"盘状凹陷"形态。结论:血链素对单独及混合培养的C.a及C.t具有显著抑制作用。血链素使C.a及C.t的对数生长期推迟。血链素可导致念珠菌C.a及C.t的菌体形态发生改变。     

血链球菌细菌素对牙龈卟啉单胞菌形貌及力学性质的影响

目的:研究血链球菌细菌素(简称血链素)对牙龈卟啉单胞菌(Porphyromonas gingivalis,P.g)形貌特征及力学性质的影响。方法:1)复苏、传代并鉴定血链球菌标准菌株ATCC10556、牙龈卟啉单胞菌标准菌株ATCC33277。2)将血链球菌低温高速离心、细胞破碎等方法提取血链素,使之作用于P.g,于37 ℃厌氧培养48 h。3)采用原子力显微镜(AFM)的接触模式,观察血链素作用前后P.g菌体的形貌变化。4)利用AFM测定血链素作用前后P.g的力-距离曲线,并计算黏附力及杨氏模量。结果:1)通过AFM的观察:P.g在血链素的作用下,菌体直径缩小、平均粗糙度及平均峰高度增加(P<0.05)。2)通过AFM的观察:血链素作用后,P.g的黏附力、杨氏模量显著降低(P<0.001)。正常P.g的黏附力平均值为(0.70±0.10) nN、杨氏模量平均值为(5.54±0.16) MPa;经血链素作用后P.g的黏附力平均值为(0.50±0.10) nN、杨氏模量平均值为(3.97±0.64) MPa。结论:1)血链素可引起牙龈卟啉单胞菌形貌特征发生改变。2)血链素可导致牙龈卟啉单胞菌的黏附力及杨氏模量降低。     

牙菌斑生物膜的细菌生长抑制因子

牙菌斑生物膜中的细菌是龋病发生的先决条件,而口腔内存在多种细菌生长的抑制因子,它们对细菌的生长或菌斑的形成起一定抑制作用。细菌生长的抑制因子主要来自宿主和细菌本身产生的细菌素以及其他代谢产物,本文就致龋菌生长抑制因子的种类及作用的研究进展作一综述。     

Caries-related bacteria and cytokines induce CXCL10 in dental pulp

Marked infiltration of inflammatory cells, such as activated T-cells, is observed in the progression of pulpitis; however, little is known about the mechanism of their recruitment into pulpal lesions. It has been recently demonstrated that CXC chemokine ligand 10 (CXCL10) chemoattracts CXC chemokine receptor 3 (CXCR3)-positive activated T-cells. We therefore examined whether CXCL10 is involved in the pathogenesis of pulpitis. CXCL10 mRNA expression levels in clinically inflamed dental pulp were higher than those in healthy dental pulp. Immunostaining results revealed that CXCL10 was detected in macrophages, endothelial cells, and fibroblasts in inflamed dental pulp, and that CXCR3 expression was observed mainly on T-cells. Moreover, cultured dental pulp fibroblasts produced CXCL10 after stimulation with live caries-related bacteria, peptidoglycans, and pro-inflammatory cytokines. In contrast, heat-killed bacteria did not induce CXCL10 secretion. These findings suggest that CXCL10-CXCR3 may play an important role in the pulpal immune response to caries-related bacterial invasion. Abbreviations: CXCL10, CXC chemokine ligand 10; CXCR3, CXC chemokine receptor 3; IFN, interferon; FBS, fetal bovine serum; LTA, lipoteichoic acid; PGN, peptidoglycan; IL, interleukin; TNF, tumor necrosis factor; PBS, phosphate-buffered saline; ELISA, enzyme-linked immunosorbent assay; CCL, C-C chemokine ligand; TLR, Toll-like receptor; NOD, nucleotide oligomerization domain; HDPF, human dental pulp fibroblasts.     

Bacteriocinogeny and the properties of some bacteriocins of streptococcus mutans

Of 143 strains of Streptococcus mutans investigated, 98 (70 per cent) were bacteriocinogenic on one or more of a series of indicator strains. The bacteriocins were active not only against other streptococcal species such as Strep. pyogenes, Strep. pneumoniae and enterococci but also against a number of unrelated Gram-positive bacteria. However, the two Gram-negative strains tested were not attacked. Many strains appeared to produce more than one type of bacteriocin and the diversity among these types was evidenced by differences in host-range patterns, sensitivity to heat, chloroform and proteolytic enzymes and, ability to diffuse through membranes. It was clear, however, from an assessment of these characteristics that bacteriocins of both the low and high molecular weight types were produced by various strains of Strep. mutans. On a world-wide basis, strains of serological type c are common and certainly predominate among local isolates. The high incidence of bacteriocinogeny among strains of this serotype, coupled with the fact that most other strains either produced or were sensitive to Strep. mutans bacteriocins, indicated that a bacteriocin typing scheme might be valuable as an epidemiological tool.     

Outcomes associated with dentists' risk assessment

OBJECTIVE: To examine retrospectively the caries-related restorative experience of at-risk individuals who received fluoride-based preventive interventions to determine if the intervention resulted in fewer caries-related procedures. METHODS: Administrative data from two dental health plans were used to determine the relationship between caries risk assessment (CRA) scores, preventive treatment and caries-related treatment procedures. We identified 45 693 adults who were consecutively enrolled for at least 1 year before and 2.5 years after the CRA. Variables representing the number of teeth with any caries-related treatment procedure and receipt of preventive treatment were created. RESULTS: The outcome variable of interest was having at least one tooth with a caries-related procedure in the 2-year follow-up period. In plan A, the recommendation for home-use fluoride was not significantly related to caries-related treatment procedures in the follow-up period for individuals at low, moderate or high risk (P > 0.300). In plan B, application of in-office fluoride was associated with having at least one tooth with a caries-related treatment procedure in the follow-up period (P < 0.001). CONCLUSIONS: We found incomplete compliance with guidelines for recommendation or administration of preventive treatment for patients at elevated risk for caries. We were also unable to identify any significant reductions in caries-related procedures for individuals receiving a fluoride intervention, compared with those who did not, when stratified by risk level.     

Trends in dental health among Icelandic urban children

Caries experience, oral hygiene and caries-related salivary parameters were recorded in a 20% representative sample of 12-year-old schoolchildren in Reykjavik, Iceland in 1991. The majority of the children was re-examined 3 years later in 1994. Trends in prevalence of caries and salivary bacteria were assessed by comparison with an analogous earlier longitudinal study (1984–87). Mean DPS values for 12-year-olds were 12.1 and 4.1, for 15-year-olds 23.3 and 11.3 in the earlier and later study, respectively. Reduction in DPS was 66% and 52% for the respective age groups. The decline was most pronounced in the group with low caries prevalence. Trends in caries experience were paralleled by salivary bacteria. The mean caries scores and frequency distributions of 15-year-olds in 1994 closely resembled those of 12-year-olds a decade earlier, suggesting a delay rather than a true fall in caries prevalence.     

Pilot study of rapid caries treatment needs screening--a brief communication

Objective: To evaluate a newly developed screening method for caries-related treatment needs. Methods: The Rapid Caries Treatment Needs Screening (RCTNS) Index includes five ordinal nominal scores. Comparisons with conventional examinations were conducted among 565 young Israeli adults (aged 23  ±  5.3 years) by the same dentist. Results: According to conventional examination, 79.5 percent demonstrated caries-related treatment needs as compared to 54.9 percent according to RCTNS. The sensitivity of RCTNS was 68.1 percent; specificity was 96.5 percent; positive predictive value was 98.7 percent; and negative predictive value was 43.9 percent. The calculated percentage of explained variance ( R ²) of the conventional examination results according to RCTNS was 55.6 percent. Conclusions: The data reveal the relevance of a rapid visual screening method for caries-related treatment needs. This is a pilot study that demands further methodological refinement. Preliminary results revealed a potential, which should be further investigated.     

Diverse activity spectra of bacteriocin-like inhibitory substances having activity against mutans streptococci

Mutans streptococci (MS) are known to be causative agents of dental caries. It has been suggested that these cariogenic bacteria could be eliminated from dental plaque by application of bacteriocins or bacteriocin-like inhibitory substances (BLIS). In the present study 272 bacterial strains of the genera Streptococcus, Enterococcus and Staphylococcus were tested for their production of BLIS activity against MS by use of a deferred antagonism test on agar media supplemented with either whole blood or yeast extract. Although only 14.3% of the test strains displayed anti-MS activity, the inhibitory agents produced by these strains were characterised by considerable diversity in the range of their inhibitory action against both MS and other common oral streptococcal species. It is suggested that combinations of relatively specifically targeted anti-MS BLIS may have potential application to the prevention of dental caries.     

Validation of a simple approach to caries risk assessment

OBJECTIVE: This study examined the predictive validity of a simple subjective method promoted to dentists for assessing their patients' caries risk. METHODS: Data from two large group practices that have used guideline-assisted caries risk assessment (CRA) for several years were analyzed retrospectively to determine the receipt of caries-related treatment following a CRA. Patient age and receipt of caries preventive treatment subsequent to the CRA were control variables in logistic regressions to determine the likelihood of caries-related treatment for low, moderate, and high risk groups. RESULTS: Among 45,693 individuals in the two plans, those categorized as being at high caries risk were approximately four times as likely to receive any caries-related treatment as those categorized as being at low caries risk. Those categorized as at moderate risk were approximately twice as likely to receive any treatment. In addition, for those at elevated risk who required any treatment, the number of teeth requiring treatment was larger. CONCLUSION: The results of this study provide the first large-scale, generalizable evidence for the validity of dentists' subjective assessment of caries risk.