Search

Objective To investigate the effect of a new powered toothbrush with tapered bristles on the brush head for the reduction of dental plaque and gingivitis. Methods This was a single-centre, single-group, longitudinal clinical trial. Thirty-two participants who were typical manual toothbrush users were recruited and assigned the sonic-powered brush. Interviews were arranged on the 1st , 4th , and 15th days which represented the baseline (T1 ), middle (T2 ) and final (T3 ) time points, respectively. At each visit, the plaque index (PlI), gingival index (GI), bleeding on probing (BOP) and probing depth (PD) were recorded for the Ramfjord index teeth, gingival crevicular fluid(GCF) samples were collected and the proportions of eight periodontal pathogenic bacteria were analysed. Repeated-measures analysis of variance (ANOVA) was used for comparisons at different time points. Results PlI was significantly reduced by 41.67% from T1 to T2 (p 0.05). Conclusion This research demonstrated the efficacy of the sonic-powered brush handle together with tapered bristles on the brush in reducing plaque and gingivitis within a short time period.

Comprehensive research on ethnic disparities in dental caries in China is limited. The aims of this cross-sectional study were to compare the levels of dental caries in adolescents between the Han ethnic group and ethnic minority groups in China and to explore the risk indicators for dental caries within ethnic subgroups. Data from the Fourth National Oral Health Survey in 2015, which covered all 31 province-level administrative divisions in mainland China, were used. The dental caries status in the permanent dentition of adolescents aged 12, 13, 14, and 15 y was measured using the decayed, missing, and filled teeth (DFMT) score, and sociodemographic characteristics and oral health–related behaviors were also collected. A total of 118,601 adolescents were included, with ethnic minority groups accounting for 13.15%. Of the Han and minority groups, the standardized prevalence of dental caries experience was 40.58% and 47.67%, and the mean DMFT scores were 0.97 and 1.28, respectively. According to the multivariate zero-inflated negative binomial regression analysis, the caries status of minorities was more severe than Han adolescents (adjusted prevalence rate ratio [PRR], 1.14; 95% confidence interval [CI], 1.10–1.18). This disparity was greater among adolescents who lived in rural areas, had mid-level economic status, and frequently consumed sugary beverages. After propensity score matchings, Uygur (PRR, 1.44; 95% CI, 1.25–1.67), Tibetan (PRR, 1.39; 95% CI, 1.3–1.48), and Yi (PRR, 1.24; 95% CI, 1.04–1.48) adolescents were significantly more likely to have caries than Han adolescents. Subgroup analyses revealed that gender, age, location of residence, economic status, region, consumption of sweet snacks and sugary beverages, and dental visit pattern were significantly associated with dental caries within ethnic minorities.

Biofilms lead to approximately 65% of infections, and these infections are hard to treat. Thus, it is crucial to identify effective antibiofilm agents with low cytotoxicity. Peptides with antibiofilm activity have been regarded as promising solutions, and peptides with MBICs (minimal biofilm inhibitory concentrations) that are lower than their minimal inhibitory concentration (MICs) (minimal inhibitory concentrations) are appealing. Therefore, we systematically summarized and classified previously reported peptides with antibiofilm activity. A total of 51 peptides with antibiofilm activity were classified into 14 categories. The MICs and MBICs of these fourteen representative peptides, one selected from each category, were compared against the Gram-positive bacterium Streptococcus mutans, the Gram-negative bacterium Pseudomonas aeruginosa, and the fungus Candida albicans. Six representative peptides (C5-pleurocidin, C6-Pac-525, C9-protegrin-1, C11-TetraF2W-RR, C13-WLBU2, and C14-melittin) showed antibiofilm activity against both bacteria and fungi, and among these 6 representative peptides, 4 peptides (C9-protegrin-1, C11-TetraF2W-RR, C13-WLBU2, and C14-melittin) could prevent biofilm formation with lower MBIC values than their MICs. CLSM (confocal laser scanning microscopy), SEM (scanning electron microscopy), and TEM (transmission electron microscopy) were further used to observe the morphologies of the biofilms after treatment with the peptides. Among the above 4 peptides, WLBU2 and melittin sparsely scattered the biofilms without destroying the bacteria. In conclusion, the currently reported peptides with antibiofilm activity are limited in number, but peptides with lower MBICs than MICs exist as promising candidates against biofilm-related infections and need further study. KEY POINTS: • Antibiofilm peptides could inhibit biofilm formation with MBICs that are lower than MICs. • The mechanism of antibiofilm peptides is not only due to antimicrobial activity.

Background With the goal to develop high efficiency oral antimicrobial agents to prevent dental caries, a collection of copper(I)-containing small molecule complexes with different substitution were synthesized and characterized. In current research, we screened these complexes and explored their antimicrobial activities, especially against cariogenic bacteria Streptococcus mutans. Methods The characterization and minimum inhibitory concentrations of these complexes have been determined by NMR spectroscopy and standard broth microdilution, respectively. Biofilm formation and morphology were evaluated using crystal violet staining, MTT, confocal laser scanning microscope and scanning electron microscope. Finally, we tested the biocompatibility. Results Cu1 was screened and presented excellent performance, which suggested that the less lipophilic and less steric copper complexes would be effective toward the bacterial. Cu1 also effectively inhibited the formation of S.mutans biofilm at its minimum inhibitory concentration. Conclusions This study demonstrates a high potential of copper(I)-containing small molecule complexes as broad-spectrum inhibitors to treat oral bacterial, especially for diminishing S.mutans biofilm formation.

Objectives This study aimed to measure socioeconomic-related inequality and horizontal inequity in the use of oral health services and decompose this inequality among adults of different age groups in China. Methods In total, 10 973 adults (3669 aged 35-44 years, 3767 aged 55-64 years and 3537 aged 65-74 years) who participated in the 4th National Oral Health Survey (2015-2016) in China were included. Concentration curves and the Erreygers-corrected concentration index (EI) were employed to measure socioeconomic-related inequality in the use of oral health services. Then, inequity in this utilization was measured by the horizontal inequity index (HI). Furthermore, decomposition analyses were conducted for the three groups to explain the contributions of income level, need factors (ie self-assessed oral health and evaluated oral health status), other factors (ie sex, residential location, educational attainment level and type of basic insurance) and a residual term to overall inequality in oral health service utilization. Results The significant positive EI and HI values indicated that pro-rich inequality and inequity in oral health service utilization exist among Chinese adults. Income and type of basic medical insurance contributed the most to socioeconomic-related inequality in the use of oral health services among adults aged 55-64 and 65-74 years. However, the main driving factors of socioeconomic inequality among adults aged 35-44 years in dental care use included income, educational achievement, type of basic medical insurance and residential location. The need variables accounted for a very small proportion of overall socioeconomic-related inequality in oral health service use in all three groups. Conclusions Oral healthcare service utilization was disproportionately concentrated among better-off Chinese adults. The primary determinants of inequality in dental care use in different age groups provide information for policymakers to create more targeted policies to achieve equity in the oral healthcare system in China.

Background: The financial burden of oral diseases is getting more important. The aim of this study was to describe the dental expenditure, analyze its progressivity and horizontal inequality under the general health finance and insurance system, and identify the key social determinants of this inequality for Chinese adults. Methods: A secondary analysis used the data of 13,464 adults from the 4 th National Oral Health Epidemiological Survey (NOHES) in China was undertook. The dental expenditure in the past year divided into out-of-pocket and health insurance payments was collected. Horizontal inequality index and Kakwani index were used to analyze the horizontal inequality and progressivity, respectively. Decomposition of concentration index was made to explore the associated socioeconomic determinants. Results: Mean dental expenditure per capita of Chinese adults was $20.55 (95% Confidence Interval, CI: 18.83,22.26) and for those who used dental service in the past year, the number was $100.95(95%CI: 93.22,108.68). More than 90% of the expenditure was out-of-pocket. Horizontal inequality indices and Kakwani indices were both negative and that indicated inequalities were in favor of the rich. The socioeconomic factors including income, urban or rural area and educational attainment were the main contributors to the inequality of dental expenditure. Conclusion: Dental expenditure for Chinese adults was not too much under a pretty low utilization. The payments of dental expenditure were regressive. People with the most oral health need didn’t meet appropriate dental services. Socioeconomic characteristic including household income, area and education was the main determinant while oral hygiene practice and self-reported oral health were the main individual determinants for the inequality of dental expenditure.

Purpose. Adherence capacity is one of the principal virulence factors of Streptococcus mutans, and adhesion virulence factors are controlled by small RNAs (sRNAs) at the post-transcriptional level in various bacteria. Here, we aimed to identify and decipher putative adhesion-related sRNAs in clinical strains of S. mutans. Methodology. RNA deep-sequencing was performed to identify potential sRNAs under different adhesion conditions. The expression of sRNAs was analysed by quantitative real-time PCR (qRT-PCR), and bioinformatic methods were used to predict the functional characteristics of sRNAs. Results. A total of 736 differentially expressed candidate sRNAs were predicted, and these included 352 sRNAs located on the antisense to mRNA (AM) and 384 sRNAs in intergenic regions (IGRs). The top 7 differentially expressed sRNAs were successfully validated by qRT-PCR in UA159, and 2 of these were further confirmed in 100 clinical isolates. Moreover, the sequences of two sRNAs were conserved in other Streptococcus species, indicating a conserved role in such closely related species. A good correlation between the expression of sRNAs and the adhesion of 100 clinical strains was observed, which, combined with GO and KEGG, provides a perspective for the comprehension of sRNA function annotation. Conclusion. This study revealed a multitude of novel putative adhesion-related sRNAs in S. mutans and contributed to a better understanding of information concerning the transcriptional regulation of adhesion in S. mutans.

Research on the association between dental caries and body mass index (BMI) in children has shown contradictory results; thus we aimed to examine the association between dental caries and the full range of BMI classes among children. We comprehensively searched PubMed, Embase, and the Cochrane Library for studies published prior to March 2017. Articles comparing dental caries among the full range of BMI classes for children below 18 years of both genders were included. Fourteen studies were eligible for this study. Basic information - i.e., first author, published year, study design, country, sample size, age, type of dental caries index and BMI, main results and conclusions, and means and standard deviations of the dental caries indexes used - was pooled. The weighted mean differences and corresponding 95% confidence intervals for dental caries between children with abnormal weight and those with normal weight were analyzed. Generally, no significant differences in caries were found between any abnormal-weight group and the normal-weight group for both primary and permanent teeth. Sensitivity analyses showed that the obese group had more caries than the normal-weight group in their primary teeth. Significantly more caries was found among the overweight and obese children in both primary and permanent teeth in high-income countries, but not in low- and middle-income countries. We recommend that further studies use suitable sample sizes, unify the criteria for BMI categorization and the dental caries index, and investigate the confounding factors that might influence dental caries and BMI.

Streptococcus mutans is a cariogenic bacterium that contributes to dental caries due to its ability to produce lactic acid, which acidifies the local environment. The potential of S. mutans to respond to environmental stress and tolerate low pH is essential for its survival and predominance in caries lesions. Small noncoding RNAs (sRNAs) have been reported to be involved in bacterial stress and virulence. Few studies have investigated the sRNAs of S. mutans and the function of these sRNAs remains to be elucidated. In the present study, the association between sRNA133474 and acid tolerance, including potential underlying mechanisms, were investigated within clinical strains of S. mutans. From pediatric dental plaques, 20 strains of S. mutans were isolated. An acid killing assay was performed to analyze acid tolerance of S. mutans. Expression patterns of sRNA133474 were investigated during various growth phases under various acidic conditions via reverse transcription‑quantitative polymerase chain reaction. RNA predator and Kyoto Encyclopedia of Genes and Genomes analyses were performed to predict target mRNAs of sRNA133474 and to examine the involvement of putative pathways of target mRNAs, respectively. The results of the present study demonstrated that sRNA133474 activity was growth phase‑dependent, and two distinct expression patterns were identified in 10 clinical strains. At pH 5.5 and 7.5 the expression levels of sRNA133474 were significantly different, and high‑acid tolerant strains exhibited reduced expression levels of sRNA133474 compared with low‑acid tolerant strains. A correlation between sRNA133474 expression levels and acid tolerance was observed in 20 clinical isolates of S. mutans (r=‑0.6298, P

Objective The aim of this study was to estimate the dental expenditure and the availability of basic medical insurance in dental service for Chinese adults. Horizontal and vertical inequalities were examined and the key social determinants were identified to potentially explain such income-related inequalities in dental expenditure. Materials and Methods A secondary analysis used the data of 13,464 adults from the 4 th National Oral Health Epidemiological Survey (NOHES) in China was undertook. The dental expenditure including out-of-pocket and health insurance payments in the past year and in 13464 participants and 2740 of who used dental service in the past year was collected. Horizontal inequality index and Kakwani index were used to analyze the horizontal and vertical financial inequality, respectively. Decomposition of concentration index was made to explore the associated socioeconomic determinants. Results Mean dental expenditure per capita of Chinese adults was $20.54 (95% CI: 18.83,22.26) and for those who used dental service in the past one year, the number was $100.95(95%CI: 93.22,108.68). More than 90% of the expenditure was out-of-pocket. Horizontal inequality indices and Kakwani indices were both negative and that indicated inequalities were in favor of the rich. The socioeconomic factors including income, urban or rural area and educational attainment were the main contributors to the inequality of dental expenditure. Conclusion Social basic medical insurances hardly work in financial risk control of oral diseases. Deficiency and waste of dental service utilization coexist. The payments of dental expenditure were regressive. Socioeconomic status was the main determinant while oral hygiene practice and oral health status were the main individual determinants for the dental expenditure.

Additional file 2: Oral health questionnaire for parents/caregivers.

Bacterial membrane vesicles (MVs) are used as a tool for intercellular communication and seem essential for bacterial survival. However, few data are available on MVs generated by Streptococcus mutans, which is the main aetiological agent of dental caries. The present study presents an integrated proteomics and metabolomics analysis of MVs isolated from S. mutans at initial pH values of 7.5 and 5.5 and explores their function. The results showed that S. mutans releases more MVs with smaller diameters under acidic conditions than under neutral conditions. Proteomic analysis showed 344 common vesicular proteins, including various virulence factors. The expressions of 140 individual proteins and 37 metabolites were altered as a result of culturing S. mutans at different pH values. Co-analyses of proteomic and metabolomics data indicated that ABC transporters underwent significant changes under acid pressure. We concluded that S. mutans produced MVs at different pH values to carry proteins associated with cariogenesis. Moreover, the alterations of S. mutans MVs under acid pressure were associated with ABC transporters. These results increase our knowledge of S. mutans MVs and imply that S. mutans MVs may play a functional role in carious infection. KEY POINTS: • S. mutans MVs contained virulence factor-related proteins, even at low pH values. • Integrated proteomics and metabolomics analysis showed that S. mutans MVs alterations under acidic conditions were associated with ABC transporters.

Streptococcus mutans and Candida albicans are often isolated from plaques associated with early childhood caries. However, there are limited studies examining how these microorganisms interact with one another and how best to manage them. Recent studies have shown that curcumin (CUR), a natural compound, has the potential to independently control both of these microorganisms. The purpose of this study was to investigate how S. mutans and C. albicans respond in mono‐ and dual‐species biofilms challenged with CUR. Quantitative biofilm biomass and viability were first evaluated and supported by live–dead PCR to assess biofilm composition. Confocal laser scanning microscopy (CLSM) was used to evaluate the exopolysaccharide (EPS) content and thickness of the biofilms, and the structure of the biofilms and morphology of the cells were observed by scanning electron microscopy (SEM). Quantitative real‐time PCR (qRT‐PCR) was applied to assess relative gene expression. The 50% minimum biofilm eradication concentration (MBEC50) of CUR against S. mutans and C. albicans was 0.5 mM. The biomass and viability decreased after treatment with CUR both in dual‐species biofilms and in mono‐species biofilm. CUR inhibited S. mutans and C. albicans in both mono‐ and dual‐species biofilms. Streptococcus mutans was more sensitive to CUR in dual‐species biofilm than in mono‐species biofilms, whereas C. albicans was less sensitive in dual‐species biofilms. EPS production was decreased by CUR in both mono‐ and dual‐species biofilms, which coincided with the downregulation of glucosyltransferase and quorum sensing‐related gene expression of S. mutans. In C. albicans, the agglutinin‐like sequence family of C. albicans was also downregulated in dual‐species biofilms. Collectively, these data show the potential benefit of using a natural antimicrobial, CUR, to control caries‐related dual‐species plaque biofilms., Curcumin, a natural compound, can inhibit oral dual‐species biofilms. The results here show that curcumin has not only inhibited the mono‐species biofilms from Streptococcus mutans and Candida albicans, but also the dual‐species biofilm formed by those two species. Exopolysaccharide production was decreased by curcumin treatment in both mono‐ and dual‐species biofilms.

With the goal of developing high-efficiency oral antimicrobial agents to prevent S. mutans biofilm formation, a collection of copper(I)-N-heterocyclic carbenes (NHCs) complexes with different substitutions was synthesized and characterized. Their inhibitory activities of Cu1–Cu7 were screened. It was found that Cu1 provided significant excellent performance, which suggested that the less lipophilic and less sterically hindered copper complexes would be effective towards the bacteria. This study demonstrates the great potential of copper(I)-containing small molecule complexes as broad-spectrum inhibitors to treat oral bacteria, especially for diminishing S. mutans biofilm formation, which opens promising perspectives for the development of new metal-NHCs for controlling the biofilm formation associated with pathogens.

Background: Analysis of emerging data shows that miRNAs, including miR-155, play important roles in tumorigenesis. Several studies have indicated that miR-155 and MIR155HG polymorphisms may be related to cancer risk, but the association was controversial. Therefore, we conducted this first-reported comprehensive meta-analysis of the association of miR-155 and MIR155HG polymorphisms with cancer risk. Materials and Methods: We searched several databases, including PubMed, Embase, and Web of Science, to identify the eligible studies reporting the association of miR-155 and MIR155HG polymorphisms with cancer risk. We calculated the pooled odds ratios (ORs) and 95% confidence intervals (CIs) to analyze the association. Stata software (version 16.0) was used to analyze the data we collected. Results: After being carefully and strictly screened, eight articles reporting on six common single-nucleotide polymorphisms consisting of 6184 cases and 6896 controls were included in this meta-analysis. The six polymorphisms included were rs767649 (T>A), rs928883 (A>G), rs2829803 (G>A), rs1893650 (T>C), rs4143370 (G>C), and rs12482371 (T>C). Our results showed that, in the overall analysis, heterozygotes increased cancer risk, with a marginal P value, compared with wild-type (OR = 1.06, 95% CI = 1.00–1.12, P = 0.062). Subsequent analyses showed that only rs767649 was associated with an increased risk of non-small-cell lung cancer (NSCLC) in an allele model (T vs. A: OR = 1.15, 95% CI = 1.04–1.26, P = 0.007), a homozygote model (TT vs. AA: OR = 1.31, 95% CI = 1.06–1.60, P = 0.011), and a recessive model (TT vs. AT + AA: OR = 1.30, 95% CI = 1.08–1.55, P = 0.005). Conclusion: The present meta-analysis indicates that the rs767649 polymorphism might be a potential factor for NSCLC risk; however, more studies should be conducted to confirm these findings.

There are signs that amyloid fibers exist in Streptococcus mutans biofilm recently. However, the characteristics of amyloid fibers and fibrillation influencing factors are unknown. In this study, we firstly used transmission electron microscopy (TEM) and atomic force microscopy (AFM) to observe the morphology of amyloid fibers in S. mutans. Then the extracted amyloid fibers from biofilm were studied for their characteristics. Further, the influencing factors, PH, temperature and eDNA, were investigated. Results showed there were mainly two morphologies of amyloid fibers in S. mutans, different in width. Amyloid fibers inhibitor-EGCG obviously destroyed biofilm at different stages, which is dose-dependent. The amount of amyloid fibers positively correlated with biofilm biomass in clinical isolates. Acidic pH and high temperature obviously accelerated amyloid fibrillation. During amyloid fibrillation, amyloid growth morphologies were observed by TEM and results showed two growth morphologies. Amyloid fibers formed complex with eDNA, which we call (a)eDNA. The molecular weight of (a)eDNA was similar to genomic DNA, greatly larger than that of eDNA in matrix. Combined use of DNase I and EGCG was more efficiently in inhibiting amyloid fibers and biofilm biomass. In conclusion, amyloid fibers are the crucial structures for S. mutans biofilm formation, showing two types of morphology. Acidic pH and temperature can obviously accelerate amyloid fibrillation. Amyloid fibers form complex with (a)eDNA and combined use of DNase and amyloid fiber inhibitor is more efficiently in inhibiting S. mutans biofilm formation. Electronic supplementary material The online version of this article (10.1186/s13568-019-0753-1) contains supplementary material, which is available to authorized users.

Additional file 1. Figure S1: The morphology of planktonic S. mutans observed by TEM. Figure S2: The characteristics of the extracted amyloid fibers.

Objective The aim of this study was to evaluate whether individual genetic factors involved in amelogenesis, the immune response and water channel proteins may increase the susceptibility to Molar-Incisor Hypomineralization (MIH) in Chinese children. Design DNA samples were collected from 86 cases with MIH cases and 344 controls. Sixteen single-nucleotide polymorphisms (SNPs) were investigated. Logistic regression analysis was performed to assess association between SNPs and the risk of MIH. Results Our results showed that the risk of MIH in the rs13115627-AA genotype carriers and the rs1784418-TT genotype carriers were significantly higher than that among those with the rs13115627-GG genotype (OR (95 % CI)) = 4.942 (0.658-37.131) and the rs1784418-CT genotype (OR (95 % CI)) = 2.023 (1.63–3.521). The population with the rs1800972‐CC genotype and the rs1800972‐C allele had a higher risk to develop MIH, OR (95 % CI) = 2.284 (1.267–4.115), OR (95 % CI) = 2.427 (1.493–3.953) respectively. In the Aquaporin 5(AQP5) gene, we individually analyzed two SNPs, rs1996315 and rs923911. We found no significant associations between them and MIH. However, in the analysis of the gene-gene interactions, we discovered a significant two‐locus model (P = 0.023) involving rs1996315 and rs923911. Participants with the rs1996315‐AG and rs923911-AC genotypes had the highest MIH risk, compared to participants with the rs1996315‐GG and rs923911-CC genotypes, OR (95 % CI) = 3.603 (1.147–11.318). Conclusion This study showed that genetic variants in the AMBN, MMP20 and DEFB1 genes may contribute to MIH in the permanent dentition of children. Moreover, interactions among AQP5 gene may also increase the MIH susceptibility.

Streptococcus mutans (S. mutans)has been proved to be the main aetiological factor in dental caries. Curcumin, a natural product, has been shown to exhibit therapeutic antibacterial activity, suggesting that curcumin may be of clinical interest. The objective of this study is to evaluate the inhibitory effects of curcumin on metabolism and biofilm formation inS. mutansusing a vitro biofilm model in an artificial oral environment.S. mutansbiofilms were treated with varying concentrations of curcumin. The biofilm metabolism and biofilm biomass were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and the crystal violet assay. Confocal laser scanning microscopy was used to analyse the composition and extracellular polysaccharide content ofS. mutansbiofilm after curcumin treatment. The biofilm structure was evaluated using a scanning electron microscope. The gene expression of virulence-related factors was assessed by real-time PCR. The antibiofilm effect of curcumin was compared with that of chlorhexidine. The sessile minimum inhibitory concentration (SMIC50%) of curcumin againstS. mutansbiofilm was 500 μM. Curcumin reduced the biofilm metabolism from 5 min to 24 h. Curcumin inhibited the quantity of live bacteria and total bacteria in both the short term (5 min) and the long term. Moreover, curcumin decreased the production of extracellular polysaccharide in the short term. The expression of genes related to extracellular polysaccharide synthesis, carbohydrate metabolism, adherence, and the two-component transduction system decreased after curcumin treatment. The chlorhexidine-treated group showed similar results. We speculate that curcumin has the capacity to be developed as an alternative agent with the potential to reduce the pathogenic traits ofS. mutansbiofilm.

To monitor the longitudinal changes in oral microbial diversity of children with severe early childhood caries (S-ECC) compared to caries free (CF) controls.Dental plaque samples of 12 children in each group at 8, 14, 20, 26 and 32 months of age were analysed. Total microbial genomic DNA was isolated from each sample, and PCR-denaturing gradient gel electrophoresis (DGGE) analyses were carried out.The number of bands was significantly higher in the CF group (18.17±4.91 bands) than in the S-ECC group (14.54±5.56 bands) at 32 months of age (P0.05). A total of 21 genera were identified in all subjects, and there were no significant differences between the two groups at genus level. DGGE profiles showed that most of the clusters were constructed from one individual over time in the both groups.The onset of S-ECC is accompanied by a decrease in microbial diversity. The overall composition of the microbiota is highly similar within an individual over time.

Streptococcus mutans (S. mutans) is the major clinical pathogen responsible for dental caries. Its acid tolerance has been identified as a significant virulence factor for its survival and cariogenicity in acidic conditions. Small RNAs (sRNAs) are recognized as key regulators of virulence and stress adaptation. Here, we constructed three libraries of sRNAs with small size exposed to acidic conditions for the first time, followed by verification using qRT-PCR. The levels of two sRNAs and target genes predicted to be bioinformatically related to acid tolerance were further evaluated under different acid stress conditions (pH 7.5, 6.5, 5.5, and 4.5) at three time points (0.5, 1, and 2 h). Meanwhile, bacterial growth characteristics and vitality were assessed. We obtained 1879 sRNAs with read counts of at least 100. One hundred and ten sRNAs were perfectly mapped to reported msRNAs in S. mutans. Ten out of 18 sRNAs were validated by qRT-PCR. The survival of bacteria declined as the acid was increased from pH 7.5 to 4.5 at each time point. The bacteria can proliferate under each pH except pH 4.5 with time. The levels of sRNAs gradually decreased from pH 7.5 to 5.5, and slightly increased in pH 4.5; however, the expression levels of target mRNAs were up-regulated in acidic conditions than in pH 7.5. These results indicate that some sRNAs are specially induced at acid stress conditions, involving acid adaptation, and provide a new insight into exploring the complex acid tolerance for S. mutans.

Objective To explore and compare the genetic polymorphisms of the sortase A (srtA) gene found in Streptococcus mutans ( S. mutans ) infecting two-year-old children suffering early childhood caries to those found in caries-free children through molecular identification methods. Methods Clinical S. mutans strains were isolated from the dental plaques of two-year-old children. Fifteen strains of S. mutans from the caries-active group and 15 strains of S. mutans from the caries-free group were collected. Genomic DNA was extracted from the S. mutans isolates. DNA fragments, including the srtA gene, were amplified by PCR. The PCR products were purified, sequenced and analyzed. A chi-square test and BioEdit software were used to analyze the sequencing results. Results All 30 clinically isolated S. mutans strains had a 741 base pair (bp) srtA gene. There were no nucleotide sequence insertions or deletions observed in the srtA genes. Twenty mutations were identified in the srtA genes that taken from the 30 clinical strains. There were 10 silent point mutations at the 78, 99, 150, 165, 186, 222, 249, 261, 312, and 636 bp positions. The other 10 mutations were point mutations resulting in a missense mutation at the 23, 34, 36, 47, 112, 114, 168, 176, 470, and 671 bp positions. None of the positions were enzyme-activity sites of srt A. The missense mutation rates of the two groups did not exhibit statistically significant differences. Conclusion There were no genetic polymorphisms of the sortase A gene associated with early childhood caries in two-year-old children.

International Journal of Paediatric Dentistry 2011; 21: 58–67 Background. In China, there is a massive rural–urban migration and the children of migrants are often unregistered residents (a ‘floating population’). Aim. This pilot study aimed to profile the oral health of migrant children in South China’s principal city of migration and identify its socio-demographic/behavioural determinants. Design. An epidemiological survey was conducted in an area of Guangzhou among 5-year-old migrant children (n = 138) who received oral examinations according to the World Health Organization criteria. Parents’ oral health knowledge/attitude, child practices, and impact of children’s oral health on their quality-of-life (QoL) were assessed. Results. The caries rate and mean (SD) dmft were 86% and 5.17 (4.16), respectively, higher than those national statistics for both rural and urban areas (P

Streptococcus mutans (S. mutans) is the major aetiological agent of dental caries, and the transpeptidase Sortase A (SrtA) plays a major role in cariogenicity. The T168G and G470A missense mutations in the srtA gene may be linked to caries susceptibility, as demonstrated in our previous studies. This study aimed to investigate the effects of these missense mutations of the srtA gene on SrtA enzyme activity in S. mutans. The point mutated recombinant S.mutans T168G and G470A sortases were expressed in expression plasmid pET32a. S. mutans UA159 sortase coding gene srtA was used as the template for point mutation. Enzymatic activity was assessed by quantifying increases in the fluorescence intensity generated when a substrate Dabcyl-QALPNTGEE-Edans was cleaved by SrtA. The kinetic constants were calculated based on the curve fit for the Michaelis-Menten equation. SrtA△N40(UA159) and the mutant enzymes, SrtA△N40(D56E) and SrtA△N40(R157H), were expressed and purified. A kinetic analysis showed that the affinity of SrtA△N40(D56E) and SrtA△N40(R157H) remained approximately equal to the affinity of SrtA△N40(UA159), as determined by the Michaelis constant (K m ). However, the catalytic rate constant (k cat ) and catalytic efficiency (k cat /K m ) of SrtA△N40(D56E) were reduced compared with those of SrtA△N40(R157H) and SrtA△N40(UA159), whereas the k cat and k cat /K m values of SrtA△N40(R157H) were slightly lower than those of SrtA△N40(UA159). The findings of this study indicate that the T168G missense mutation of the srtA gene results in a significant reduction in enzymatic activity compared with S. mutans UA159, suggesting that the T168G missense mutation of the srtA gene may be related to low cariogenicity.

Background The factors involved in Streptococcus mutans colonization in young children are not clear. The aim of this study was to determine the factors associated with S. mutans colonization in 8- to 32-month-old children. Methods A group of 225 caries-free 8-month-old children was recruited for the study. They were examined every six months until they were 32 months old to investigate their environmental factors, host factors and bacterial transmission factors. At baseline and during each examination, their teeth were checked for the presence of dental plaque and developmental defects of enamel, and S. mutans plaque status was assessed using a real-time PCR test. Results Eight children (3.6%) showed S. mutans colonization by the age of 8 months. The percentages of colonization were 6.0% at 14 months, 16.2% at 20 months, 26.7% at 26 months, and 33.5% at 32 months. The results showed that females (p = 0.006), children with enamel hypoplasia (p = 0.024), children with low birth weights (p = 0.005), those who consume more sweets (p