Tansmission, diversity and virulence factors of Sreptococcus mutans genotypes

Current appraises of therapeutic applications of nanocurcumin: A novel drug delivery approach for biomaterials in dentistry

Curcumin is a natural herb and polyphenol that is obtained from the medicinal plant Curcuma longa. It's anti-bacterial, anti-inflammatory, anti-cancer, anti-mutagenic, antioxidant and antifungal properties can be leveraged to treat a myriad of oral and systemic diseases. However, natural curcumin has weak solubility, limited bioavailability and undergoes rapid degradation, which severely limits its therapeutic potential. To overcome these drawbacks, nanocurcumin (nCur) formulations have been developed for improved biomaterial delivery and enhanced treatment outcomes. This novel biomaterial holds tremendous promise for the treatment of various oral diseases, the majority of which are caused by dental biofilm. These include dental caries, periodontal disease, root canal infection and peri-implant diseases, as well as other non-biofilm mediated oral diseases such as oral cancer and oral lichen planus. A number of in-vitro studies have demonstrated the antibacterial efficacy of nCur in various formulations against common oral pathogens such as S. mutans, P. gingivalis and E. faecalis, which are strongly associated with dental caries, periodontitis and root canal infection, respectively. In addition, some clinical studies were suggestive of the notion that nCur can indeed enhance the clinical outcomes of oral diseases such as periodontitis and oral lichen planus, but the level of evidence was very low due to the small number of studies and the methodological limitations of the available studies. The versatility of nCur to treat a diverse range of oral diseases augurs well for its future in dentistry, as reflected by rapid pace in which studies pertaining to this topic are published in the scientific literature. In order to keep abreast of the latest development of nCur in dentistry, this narrative review was undertaken. The aim of this narrative review is to provide a contemporaneous update of the chemistry, properties, mechanism of action, and scientific evidence behind the usage of nCur in dentistry.

Genetic variation in the glucosyltransferase-B gene of Streptococcus mutans and its relationship with caries experience in children from Córdoba, Argentina, and with strains from other countries

BACKGROUND

Caries is a worldwide distributed oral disease of multifactorial nature, with Streptococcus mutans being the most commonly isolated bacterial agent. The glycosyltransferases of this bacterium would play an essential role in the aetiology and pathogenesis of caries.

AIM

We explored how the glucosyltransferase-B (gtf-B) gene variability of S. mutans from children in central Argentina correlated with their caries experience and how these strains were genetically related to those of other countries.

DESIGN

Dental examinations were performed on 59 children; dmft and DMFT indexes were calculated. From stimulated saliva, S. mutans was grown and counted (CFU/mL). From bacterial DNA, the gtf-B gene was amplified and sequenced. Alleles were identified and their genealogical relationships established. Clinical, microbiological, and genetic variables were correlated with caries experience. Our sequences were included in a matrix with those from 16 countries (n = 358); genealogical relationships among alleles were obtained. Population genetic analyses were performed for countries with >20 sequences.

RESULTS

The mean dmft + DMFT was 6.45. Twenty-two gtf-B alleles were identified here, which showed low genetic differentiation in the network. Caries experience was correlated with CFU/mL, but not with allele variation. Low differentiation was found among the 70 alleles recovered from the 358 sequences and among the countries analyzed.

CONCLUSION

In this study, caries experience in children was correlated with the number of CFU/mL of S. mutans but not with the gtf-B gene variability. Combined genetic analyses of worldwide strains support the theory that this bacterium experienced population expansions, probably associated with agriculture development and/or food industrialization.

Genetic aspects of dental caries

Dental caries is a common chronic disease affecting humans in all age groups. Various factors can affect the formation of caries including demineralization and remineralization processes with oral flora; dietary and oral hygiene habits; salivary composition, flow rate, pH and buffering capacity; morphological features of the teeth; fluoride exposures, environmental and socioeconomic factors. One of the most important factors causing inter-individual variations in caries susceptibility is the host genetics. Several genes affect individual caries susceptibility. Genes play a role in immune response, development of saliva and tooth enamel. The present review aims to overview the literature focusing on the genetic features of dental caries.

The effect of cranberry juice and a cranberry functional beverage on the growth and metabolic activity of selected oral bacteria

BACKGROUND

The oral microbiota is a significant risk indicator for oral diseases, such as dental caries and periodontal inflammation. Much attention is presently paid to the development of functional foods (e.g. beverages containing cranberry constituents, or foods containing probiotics) that may serve as adjuncts for oral disease treatments (e.g. periodontitis and caries). Cranberry fruit, due to its unique chemical composition and antimicrobial potential, is a possible ingredient of such foods. The study aimed to investigate the effects of cranberry juice (CJ) and a cranberry functional beverage (mixture of 80% v/v apple juice, 20% v/v cranberry juice, and 0.25 g/100 mL ground cinnamon; CFB) on the growth and metabolic activity of selected oral bacteria.

METHODS

Serial dilution pour plate method (SDPP) was used to examine the effect of CJ and CFB on the growth of Actinomyces naeslundii, Streptococcus mutans, and Lactobacillus paracasei subsp. paracasei. 48-h electrical impedance measurements (EIM) during the cultivation of A. naeslundii were applied to evaluate the utility of the method as a rapid alternative for the assessment of the antimicrobial potential of cranberry beverages.

RESULTS

The tested bacteria differed in their susceptibility to the antimicrobial action of CJ and CFB, with L. paracasei subsp. paracasei being least vulnerable to CFB (according to SDPP). Although CJ at a concentration of 0.5 mL/mL, showed a bactericidal effect on the growth of S. mutans, A. naeslundii was more sensitive to CJ (SDPP). Its inhibitory effect on A. naeslundii was seen even at concentrations as small as 0.03125-0.125 mL/mL (SDPP and EIM). On the other hand, S. mutans seemed to be more vulnerable to CFB than A. naeslundii (SDPP).

CONCLUSIONS

CFB may be considered an adjunct in the treatment of oral diseases due to its action against selected oral pathogens, and not against the presumably beneficial L. paracasei subsp. paracasei. Bioelectrical impedance measurements appear to be a quick alternative to evaluating the antimicrobial activity of fruit beverages, but their utility should be confirmed with tests on other bacteria.

Acidogenic and aciduric properties of Streptococcus mutans serotype c according to its genomic variability

Streptococcus mutans (S. mutans) has a wide genetic diversity that contributes to its phenotypic heterogeneity, and may be related to attributes associated with acidogenicity and aciduricity. The aim of this study was to evaluate the acidogenic and aciduric properties of S. mutans serotype c isolates from saliva of schoolchildren according to the genomic variability. S. mutans isolates were identified by polymerase chain reaction. Fifty S. mutans serotype c isolates were genotyped by pulsed field gel electrophoresis and tested for their ability to produce and resist acid. Three specific genotypes were identified in the caries-active group and only one in the caries-free group. Although isolates were similarly acidogenic, an exclusive caries-active genotype had the greatest glycolytic activity. In contrast, isolates exhibited variable aciduricity, and three caries-active genotypes were the least aciduric. We concluded that there is genetic variability within serotype c. Acid production was similar regardless of the caries status but correlated with the number of genotypes. In addition, resistance to acid could be an important characteristic for the establishment and colonisation of specific genotypes in children with caries. However, it is important to evaluate children's intrinsic characteristics and other phenotypic properties to explain the physiopathological behaviour of the different genotypes.

Antimicrobial and Antibiofilm Activity of the Probiotic Strain Streptococcus salivarius K12 against Oral Potential Pathogens

Oral probiotics are increasingly used in the harmonization of the oral microbiota in the prevention or therapy of various oral diseases. Investigation of the antimicrobial activity of the bacteriocinogenic strain Streptococcus salivarius K12 against oral pathogens shows promising results, not only in suppressing growth, but also in eliminating biofilm formation. Based on these findings, we decided to investigate the antimicrobial and antibiofilm activity of the neutralized cell-free supernatant (nCFS) of S. salivarius K12 at various concentrations against selected potential oral pathogens under in vitro conditions on polystyrene microtiter plates. The nCFS of S. salivarius K12 significantly reduced growth (p < 0.01) in Streptococcus mutans Clarke with increasing concentration from 15 to 60 mg/mL and also in Staphylococcus hominis 41/6 at a concentration of 60 mg/mL (p < 0.001). Biofilm formation significantly decreased (p < 0.001) in Schaalia odontolytica P10 at nCFS concentrations of 60 and 30 mg/mL. Biofilm inhibition (p < 0.001) was also observed in Enterobacter cloacae 4/2 at a concentration of 60 mg/mL. In Schaalia odontolytica P10 and Enterobacter cloacae 4/2, the nCFS had no effect on their growth.

The Impact of Photosensitizer Selection on Bactericidal Efficacy Of PDT against Cariogenic Biofilms: A Systematic Review and Meta-Analysis

BACKGROUND

There are investigations on multiple photosensitizers for modulation of caries-related biofilms using PDT. However, much controversy remains about recommended parameters mostly on the selection of an efficient photosensitizer.

OBJECTIVE

The study performed a systematic review to identify the answer to the following question: What photosensitizers present high bactericidal efficacy against cariogenic biofilms?

METHODS

Systematic review with meta-analyses were carried out for English language articles from October to December 2019 (PRISMA standards) using MEDLINE, Scopus, Biomed Central, EMBASE, LILACS, and Web of Science. Information on study design, biofilm model, photosensitizer, light source, energy delivery, the incubation time for photosensitizer, and bacterial reduction outcomes were recorded. We performed two meta-analyses to compare bacterial reduction, data was expressed by (1) base 10 Logarithm values and (2) Log reduction RESULTS: After the eligibility criteria were applied (PEDro scale), the selected studies showed that toluidine Blue Ortho (TBO) and methylene blue (MBO) (5-min incubation time and 5-min irradiation) demonstrated better bacterial reduction outcomes. For the data expressed by Log TBO, MBO, curcumin, and Photogem® presented a significant bacterial decrease in comparison to the control (p = 0.042). For the data represented by Log reduction, the bacterial reduction toward S.mutans was not significant for any photosensitizer (p = 0.679).

CONCLUSION

The lack of methodological standardization among the studies still hinders the establishment of photosensitizer and bactericidal efficiency. TBO, MBO, curcumin, and photogem generate greater PDT-based bacterial reduction on caries-related bacteria.. Further clinical studies are necessary in order to obtain conclusive results.

The enhancing antibiofilm activity of curcumin on Streptococcus mutans strains from severe early childhood caries

BACKGROUND

Streptococcus mutans (S. mutans) is one of the main cariogenic bacteria for caries. It was found that the clinical strains of S. mutans isolated from caries active population have stronger cariogenic ability than the isolates from caries-free (CF) people. Previous studies have found that curcumin can inhibit biofilm formation of S. mutans UA159. The objective of this study is to explore the antibiofilm effect of curcumin on the clinical isolates of S. mutans from severe early childhood caries(SECC).

RESULTS

The isolates from SECC group had more biomass than CF group (t = 4.296, P < 0.001). The acidogenicity and aciduricity of the strains from two groups showed no significant difference. After treatment with curcumin, the viability of biofilm was reduced to 61.865% ± 7.108% in SECC and to 84.059% ± 10.227% in CF group at 24 h (P < 0.05). The net reduction of live bacteria and total bacteria in the SECC group was significantly higher than that of the CF group (live bacteria t = 3.305, P = 0.016; total bacteria t = 2.378, P = 0.045) at 5 min. For 24 h, the net reduction of live bacteria and total bacteria in the SECC group was significantly higher than that of the CF group (live bacteria t = 3.305, P = 0.016; total bacteria t = 2.378, P = 0.045). The reduction of biofilm thickness reduced significantly in 5 min (t = 4.110, P = 0.015) and in 24 h (t = 3.453, P = 0.014). Long-term (24 h) curcumin treatment inhibited the amount of EPS in SECC group from (25.980 ± 1.156) μm³/μm² to (20.136 ± 1.042) μm³/μm², the difference was statistically significant (t = 7.510, P < 0.001). The gene of gtfC, gtfD, ftf, gbpB, fruA and srtA in the CF group and the gtfB, gtfC, gtfD, ftf, gbpB, srtA in SECC group were respectively reduced after 5 min curcumin treatment. After 24 h treatment, the gtfB, gtfC, gtfD, ftf, gbpB, fruA and srtA in both two groups were downregulation, all the differences were statistically significant.

CONCLUSIONS

Curcumin has antibiofilm activity on clinical strains of S. mutans, especially for those isolated from SECC.

Formulation and characterization of antibacterial orthodontic adhesive

OBJECTIVE

The objective of this study was to formulate experimental orthodontic bracket adhesives and test their mechanical properties, fluoride release and antibacterial activity.

METHODS

Four experimental antibacterial orthodontic bracket adhesives were prepared with different compositions of synthesized antibacterial monomers replacing total 5% of dental monomers in the control Transbond XT (3M): 5%C11, 3.5%C11+1.5%C2, 5%C16, and 3.5%C16+1.5%C2. Transbond XT alone was used as control. These groups were used to bond premolar brackets to extracted premolars. Shear bond strength (SBS) was tested using an Instron machine. For antibacterial test, disk specimens (10mm diameter, 1mm thick, n=4) were fabricated and incubated with cultures of cariogenic Streptococcus mutans for 48h, and following gentle sonication, S. mutans biofilms in colony-forming-units (CFU) on the disks were enumerated by plating on agar medium. The data were analyzed using ANOVA and Tukey test (α=0.05).

RESULTS

All experimental groups had similar shear bond strength (no significant difference) to the control. All experimental groups showed significant inhibitory effect against S. mutans biofilm formation, when compared to the control, but there was no significant difference between experimental groups.

CONCLUSION

Antibacterial orthodontic adhesive can be fabricated to have similar mechanical properties but better caries-inhibitory effect than current adhesive.

The effect of aging methods on the fracture toughness and physical stability of an oxirane/acrylate, ormocer, and Bis-GMA-based resin composites

PURPOSE

To determine the effect of aging methods on the fracture toughness of a conventional Bis-GMA-based resin composite (Filtek Supreme), an ormocer-based resin composite (Admira), and an experimental hydrophobic oxirane/acrylate interpenetrating network resin system (OASys)-based composite.

METHODS

A 25 × 5 × 2.8-mm stainless-steel mold with 2.5 mm single-edge center notch, following ASTM standards [E399-90], was used to fabricate 135 specimens (n = 15) of the composite materials and randomly distributed into groups. For the baseline group, specimens were fabricated and then tested after 24-h storage in water. For the biofilm challenge, specimens were randomly placed in a six-well tissue culture plate and kept at 37 °C with bacterial growth media (Brain Heart Infusion (BHI); Streptococcus mutans) changed daily for 15 days. For the water storage challenge, specimens were kept in 5 ml of deionized distilled autoclaved water for 30 days at 37 °C. μCT evaluation by scanning the specimens was performed before and after the proposed challenge. Fracture toughness (K_Ic) testing was carried out following the challenges.

RESULTS

μCT surface area and volume analyses showed no significant changes regardless of the materials tested or the challenge. Filtek and Admira fracture toughness was significantly lower after the biofilm and water storage challenges. OASys mean fracture toughness values after water aging were significantly higher than that of baseline. Toughness values for OASys composites after biofilm aging were not statistically different when compared to either water or baseline values.

CONCLUSION

The fracture toughness of Bis-GMA and ormocer-based dental resin composites significantly decreased under water and bacterial biofilm assault. However, such degradation in fracture toughness was not visible in OASys-based composites.

CLINICAL SIGNIFICANCE

Current commercial dental composites are affected by the oral environment, which might contribute to the long-term performance of these materials.

The Biology of Streptococcus mutans

As a major etiological agent of human dental caries, Streptococcus mutans resides primarily in biofilms that form on the tooth surfaces, also known as dental plaque. In addition to caries, S. mutans is responsible for cases of infective endocarditis with a subset of strains being indirectly implicated with the onset of additional extraoral pathologies. During the past 4 decades, functional studies of S. mutans have focused on understanding the molecular mechanisms the organism employs to form robust biofilms on tooth surfaces, to rapidly metabolize a wide variety of carbohydrates obtained from the host diet, and to survive numerous (and frequent) environmental challenges encountered in oral biofilms. In these areas of research, S. mutans has served as a model organism for ground-breaking new discoveries that have, at times, challenged long-standing dogmas based on bacterial paradigms such as Escherichia coli and Bacillus subtilis. In addition to sections dedicated to carbohydrate metabolism, biofilm formation, and stress responses, this article discusses newer developments in S. mutans biology research, namely, how S. mutans interspecies and cross-kingdom interactions dictate the development and pathogenic potential of oral biofilms and how next-generation sequencing technologies have led to a much better understanding of the physiology and diversity of S. mutans as a species.

Genotypic diversity of Streptococcus mutans isolated from preschoolers with and without early dental care

Abstract Introduction Streptococcus mutans (S. mutans) exhibits extensive genotypic diversity, but the role of this variation is poorly understood. Objective To evaluate the genotypic diversity of S. mutans in preschoolers with and without early dental care and to associate it with dental caries experience. Material and method Twenty children, aged five year old, with history of dental care since they were one year old (G1) and 20 children without history of dental care (G2) were included. Their oral health status was assessed by the dmft index. S. mutans samples were isolated from the saliva and analysed by polymerase chain reaction. A total of 339 S. mutans isolates (173 from G1 and 166 from G2) were genotyped by random amplified polymorphic DNA with arbitrary primers OPA-02 and OPA-13. Result The results revealed 75 distinct genotypes of S. mutans in G1 and 73 in G2. Furthermore, G1 and G2 subjects harboured one to eight and one to seven distinct genotypes of S. mutans, respectively. A statistically significant association (P=0.021) and a moderate correlation (r= 0.503) were observed between dental caries experience and genotypic diversity of S. mutans in G1. Conclusion From the limitations of the study design, we just can hypothesize that actions of early dental care carried out by an educative-preventive program can contribute to a distinct oral microbiota.

Evaluating Streptococcus mutans Strain Dependent Characteristics in a Polymicrobial Biofilm Community

Aim: The purpose of this study was to investigate strain dependent differences of the cariogenic biofilm forming Streptococcus mutans within both simple and complex communities. Methods: A mono-species containing representative S. mutans clinical isolates (caries and non-caries), and a multispecies in vitro caries biofilm model containing Lactobacillus casei, Veillonella dispar, Fusobacterium nucleatum and Actinomyces naeslundii, and either of two representative S. mutans clinical isolates (caries and non-caries), was developed as a comparison model. Compositional analysis of total and live bacteria within biofilms, and transcriptional analysis of biofilm associated virulence factors were evaluated by live/dead PCR and quantitative PCR, respectively. Scanning electron microscopy (SEM) was used to analyze the architecture of biofilm. One-way analysis of variance and t-tests were used to investigate significant differences between independent groups of data. Results: Within a mono-species biofilm, different S. mutans strains responded similarly to one another during biofilm formation in different carbohydrate sources, with sucrose showing the highest levels of biofilm biomass and galactose showing the lowest. Within the polymicrobial biofilm system, compositional analysis of the bacteria within the biofilm showed that S. mutans derived from a caries-free patient was preferentially composed of both total and viable L. casei, whereas S. mutans derived from a caries patient was dominated by both total and viable S. mutans (p < 0.001). Normalized gene expression analysis of srtA, gtfB, ftf, spaP, gbpB, and luxS, showed a general upregulation within the S. mutans dominant biofilm. Conclusion: We were able to demonstrate that individual strains derived from different patients exhibited altered biofilm characteristics, which were not obvious within a simple mono-species biofilm model. Influencing the environmental conditions changed the composition and functionality S. mutans within the polymicrobial biofilm. The biofilm model described herein provides a novel and reproducible method of assessing the impact on the biofilm microbiome upon different environmental influences.

Relationship between the genetic polymorphisms of vicR and vicK Streptococcus mutans genes and early childhood caries in two-year-old children

Background

The VicRK two-component signalling system regulates virulence and cariogenicity in Streptococcus mutans (S. mutans). The purpose of this study was to explore the genetic polymorphisms of the vicR and vicK genes, which are associated with dental caries in children with S. mutans.

Methods

In this study, 121 (from each group) clinical S. mutans strains were isolated from caries-free children and children with high-severity caries to sequence the vicR and vicK genes. Genomic DNA was extracted from S. mutans strains and amplified using PCR. The PCR products were purified and sequenced. A chi-squared test and ABI Variant Reporter software were used to analyse the sequencing results.

Results

The 242 clinically isolated S. mutans strains contained the full-length vicR and vicK genes. No nucleotide sequence insertions or deletions were observed in the two genes. Four silent point mutations were identified in the vicR genes, and no missense mutations could be detected. Forty-one mutations were identified in the vicK genes. In addition to 32 silent mutations, 9 missense mutations at the 173, 337, 470, 1051, 1132, 1258, 1260, 1277, and 1348 bp positions were found. The distribution frequencies of the missense mutations were not significantly different between the groups, except for the C470T mutation. The frequency of the C470T missense mutation was higher in the high-severity caries group than in the caries-free group.

Conclusions

vicR sequences are highly conserved in S. mutans clinical isolates. The locus 470 missense mutation of the vicK gene may be related to caries in children with S. mutans.

Genotypic characterization and comparison of Streptococcus mutans in American Indian and Southeast Iowa children

Early childhood caries is a complex health care issue that has a multifactorial etiology. One aspect of this etiology is the colonization and propagation of acidogenic bacteria at an early age. There have been several bacterial species associated with caries but 1 common species is Streptococcus mutans. Here, we describe genotypic diversity and commonality of Streptococcus mutans recovered from children representing 2 groups with similar socioeconomic demographics: a Northern Plains American Indian Tribe and a Southeast Iowa population. Forty 36‐month‐old American Indian children were selected from a cohort of 239 mothers and children, and forty 2‐ to 5‐year‐old children from Southeast Iowa were selected to compare the genotypic profiles of Streptococcus mutans recovered from each child's plaque. S. mutans isolates were selected from whole mouth plaque samples; DNA was extracted and amplified via AP‐PCR to show specific genotype patterns. These patterns were compared with GelComparIIv6.5 gel analysis software. We found 18 distinct genotypes from 524 isolates; 13 of which were common between the 2 communities. Five genotypes were unique to only the American Indian children while the Southeast Iowa children harbored no unique genotypes. Although the American Indian children had some genotypes that were not present in the Southeast Iowa children, these were not widely distributed among the community. Furthermore, the levels of genotypic diversity and commonality were similar between the 2 populations. This study sets the groundwork for a comprehensive comparison of genotypes and caries among larger subsections of both populations.

In Vitro and In Vivo Biofilm Formation by Pathogenic Streptococci

This manuscript presents novel approaches to grow and evaluate Streptococcal biofilm formation using the human respiratory pathogen Streptococcus pneumoniae (the pneumococcus) as the main model organism on biological surfaces in vitro and in vivo. Most biofilm models are based on growth on abiotic surfaces, which is relevant for many pathogens whose growth on surfaces or medical devices is a major cause of disease transmission and infections, especially in hospital environments. However, most infections with commensal organisms require biofilm formation on biological surfaces in the host at the site of colonization or infection. In vitro model systems incorporating biological components from the host and taking into account the host environment of the infectious site are not well described.In a series of publications, we have shown that S. pneumoniae form complex biofilms in the nasopharynx of mice and have devised methodology to evaluate the biofilm structure and function in this environment. We have also been able to recapitulate this biofilm phenotype in vitro by incorporating crucial factors associated with the host environment. Although the protocols presented in this manuscript are focused on S. pneumoniae, the same methodology can and has been used for other Streptococcal species that form biofilms on mucosal surfaces.

Effect of silver nanoparticles on the physicochemical and antimicrobial properties of an orthodontic adhesive

OBJECTIVE

This study aimed to incorporate silver nanoparticle solutions (AgNP) in an orthodontic adhesive and evaluate its physicochemical and antimicrobial properties.

MATERIAL AND METHODS

Silver nanoparticle solutions were added to a commercial adhesive in different concentrations (w/w): 0%, 0.11%, 0.18%, and 0.33%. Shear bond strength (SBS) test was performed after bonding metal brackets to enamel. Raman spectroscopy was used to analyze in situ the degree of conversion (DC) of the adhesive layer. The surface free energy (SFE) was evaluated after the measurement of contact angles. Growth inhibition of Streptococcus mutans in liquid and solid media was determined by colony-forming unit count and inhibition halo, respectively. One-way ANOVA was performed for SBS, DC, SFE, and growth inhibition.

RESULTS

The incorporation of AgNP solution decreased the SBS (p<0.001) and DC in situ (p<0.001) values. SFE decreased after addition of 0.18% and 0.33% AgNP. Growth inhibition of S. mutans in liquid media was obtained after silver addition (p<0.05).

CONCLUSIONS

The addition of AgNP solutions to Transbond™ XT adhesive primer inhibited S. mutans growth. SBS, DC, and SFE values decreased after incorporation up to 0.33% AgNP solution without compromising the chemical and physical properties of the adhesive.

Uncovering oral Neisseria tropism and persistence using metagenomic sequencing

Microbial epidemiology and population genomics have previously been carried out near-exclusively for organisms grown in vitro. Metagenomics helps to overcome this limitation, but it is still challenging to achieve strain-level characterization of microorganisms from culture-independent data with sufficient resolution for epidemiological modelling. Here, we have developed multiple complementary approaches that can be combined to profile and track individual microbial strains. To specifically profile highly recombinant neisseriae from oral metagenomes, we integrated four metagenomic analysis techniques: single nucleotide polymorphisms in the clade's core genome, DNA uptake sequence signatures, metagenomic multilocus sequence typing and strain-specific marker genes. We applied these tools to 520 oral metagenomes from the Human Microbiome Project, finding evidence of site tropism and temporal intra-subject strain retention. Although the opportunistic pathogen Neisseria meningitidis is enriched for colonization in the throat, N. flavescens and N. subflava populate the tongue dorsum, and N. sicca, N. mucosa and N. elongata the gingival plaque. The buccal mucosa appeared as an intermediate ecological niche between the plaque and the tongue. The resulting approaches to metagenomic strain profiling are generalizable and can be extended to other organisms and microbiomes across environments.

Genetic polymorphisms of the sortase A gene and social-behavioural factors associated with caries in children: a case-control study

Background

Streptococcus mutans (S. mutans) is the primary etiological agent of dental caries. Sortase is a transpeptidase that anchors several surface proteins to the S. mutans cell wall and has been shown to play a major role in cariogenicity. The purpose of this study was to explore the genetic polymorphisms of the sortase gene (srtA) and the social-behavioural factors associated with dental caries in children with S. mutans.

Methods

In this case–control study, 121 S. mutans strains were separately selected from caries-free children and high-severity caries children for sequencing of the srtA gene. Social and behavioural data were collected by self-administered questionnaires. Genomic DNA was extracted from S. mutans strains and amplified by PCR to obtain the srtA gene. The purified PCR products were sequenced and analysed for mutations with ABI Variant Reporter software. The distribution of missense mutations and the mean of social-behavioural factors were compared between the groups. A multiple logistic regression model was used to control for confounding factors.

Results

The mutation frequencies at loci 168 (P = 0.023) and 470 (P = 0.032) were significantly different between the groups. The best-fitting model showed that greater age, high frequencies of solid sugar consumption, prolonged breastfeeding, a high proportion of visible plaque, and S. mutans with a T at locus 168 of the srtA gene were associated with high-severity caries in children (P < 0.05). Children carrying a G at locus 168 of S. mutans had a decreased risk for high-severity caries (OR = 0.32, 95% CI = 0.12–0.86) compared with those carrying a T.

Conclusions

The present study suggested that the locus 168 missense mutation of the srtA gene may correlate with caries susceptibility in children with S. mutans. In addition, age, duration of breastfeeding, solid sugar consumption, and poor oral hygiene contributed to this complex disease.

Inhibitory Effects of Chrysanthemum boreale Essential Oil on Biofilm Formation and Virulence Factor Expression of Streptococcus mutans

The aim of the study was to evaluate the antibacterial activity of essential oil extracted from Chrysanthemum boreale (C. boreale) on Streptococcus mutans (S. mutans). To investigate anticariogenic properties, and bacterial growth, acid production, biofilm formation, bacterial adherence of S. mutans were evaluated. Then gene expression of several virulence factors was also evaluated. C. boreale essential oil exhibited significant inhibition of bacterial growth, adherence capacity, and acid production of S. mutans at concentrations 0.1-0.5 mg/mL and 0.25-0.5 mg/mL, respectively. The safranin staining and scanning electron microscopy results showed that the biofilm formation was also inhibited. The result of live/dead staining showed the bactericidal effect. Furthermore, real-time PCR analysis showed that the gene expression of some virulence factors such as gtfB, gtfC, gtfD, gbpB, spaP, brpA, relA, and vicR of S. mutans was significantly decreased in a dose dependent manner. In GC and GC-MS analysis, seventy-two compounds were identified in the oil, representing 85.42% of the total oil. The major components were camphor (20.89%), β-caryophyllene (5.71%), α-thujone (5.46%), piperitone (5.27%), epi-sesquiphellandrene (5.16%), α-pinene (4.97%), 1,8-cineole (4.52%), β-pinene (4.45%), and camphene (4.19%). These results suggest that C. boreale essential oil may inhibit growth, adhesion, acid tolerance, and biofilm formation of S. mutans through the partial inhibition of several of these virulence factors.

Children with severe early childhood caries: streptococci genetic strains within carious and white spot lesions

Background and objectives

Mutans streptococci (MS) are one of the major microbiological determinants of dental caries. The objectives of this study are to identify distinct MS and non-MS streptococci strains that are located at carious sites and non-carious enamel surfaces in children with severe early childhood caries (S-ECC), and assess if cariogenic MS and non-cariogenic streptococci might independently exist as primary bacterial strains on distinct sites within the dentition of individual children.

Design

Dental plaque from children (N=20; aged 3–6) with S-ECC was collected from carious lesions (CLs), white spot lesions (WSLs) and non-carious enamel surfaces. Streptococcal isolates (N=10–20) from each site were subjected to polymerase chain reaction (PCR) to identify MS, and arbitrarily primed-PCR for assignment of genetic strains. Primary strains were identified as ≥50% of the total isolates surveyed at any site. In several cases, strains were characterized for acidurity using ATP-driven bioluminescence and subjected to PCR-determination of potential MS virulence products. Identification of non-MS was determined by 16S rRNA gene sequencing.

Results

Sixty-four independent MS or non-MS streptococcal strains were identified. All children contained 1–6 strains. In many patients (N=11), single primary MS strains were identified throughout the dentition. In other patients (N=4), primary MS strains were identified within CLs that were distinct from primary strains found on enamel. Streptococcus gordonii strains were identified as primary strains on enamel or WSLs in four children, and in general were less aciduric than MS strains.

Conclusions

Many children with S-ECC contained only a single primary MS strain that was present in both carious and non-carious sites. In some cases, MS and non-cariogenic S. gordonii strains were found to independently exist as dominant strains at different locations within the dentition of individual children, and the aciduric potential of these strains may influence susceptibility in the development of CLs.

An innovative approach to treating dental decay in children. A new anti-caries agent

The aim of this work is to evaluate the antimicrobial and cytotoxic activity of a formulation containing silver nanoparticles and chitosan, provisionally called nano silver fluoride (NSF), against Streptococcus mutans in comparison to chlorhexidine and silver diamine fluoride (SDF). The product was characterised by transmission electron microscopy and UV-Vis absorption spectroscopy. The minimum inhibition concentration (MIC) was evaluated by the spectrophotometric microdilution method and turbidity. The minimum bactericide concentration (MBC) was evaluated in brain heart infusion plates, and cytotoxicity was evaluated by haemolytic activity. The MIC and MBC for NSF were, respectively, 33.54 ± 14.52 and 50.32 µg/mL; for SDF were 33.33 ± 14.43 and 50.0 µg/mL, respectively; and for CHX were 3.3 ± 0.5 and 6 µg/mL, respectively. An ANOVA for MIC gave P = 0.032, and for MBC P = 0.035. The cytotoxic effect of NSF compared to SDF demonstrated a statistically significant difference in the MIC value (t test P < 0.05). The NSF formulation may be effective against S. mutans with much lower doses, may have lower toxicity than SDF, and may not stain teeth.

Factors associated with colonization of Streptococcus mutans in 8- to 32-month-old children: a cohort study

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 < 0.001), and those with a higher proportion of visible plaque (p = 0.020 and p = 0.041) were more likely to be colonized by S. mutans.

CONCLUSIONS

Streptococcus mutans colonization in young children was associated with gender, tooth enamel hypoplasia, low birth weight, frequent consumption of sweets and poor oral hygiene.

The effect of a silver nanoparticle polysaccharide system on streptococcal and saliva-derived biofilms

In this work, we studied the antimicrobial properties of a nanocomposite system based on a lactose-substituted chitosan and silver nanoparticles: Chitlac-nAg. Twofold serial dilutions of the colloidal Chitlac-nAg solution were both tested on Streptococcus mitis, Streptococcus mutans, and Streptococcus oralis planktonic phase and biofilm growth mode as well as on saliva samples. The minimum inhibitory and bactericidal concentrations of Chitlac-nAg were evaluated together with its effect on sessile cell viability, as well as both on biofilm formation and on preformed biofilm. In respect to the planktonic bacteria, Chitlac-nAg showed an inhibitory/bactericidal effect against all streptococcal strains at 0.1% (v/v), except for S. mitis ATCC 6249 that was inhibited at one step less. On preformed biofilm, Chitlac-nAg at a value of 0.2%, was able to inhibit the bacterial growth on the supernatant phase as well as on the mature biofilm. For S. mitis ATCC 6249, the biofilm inhibitory concentration of Chitlac-nAg was 0.1%. At sub-inhibitory concentrations, the Streptococcal strains adhesion capability on a polystyrene surface showed a general reduction following a concentration-dependent-way; a similar effect was obtained for the metabolic biofilm activity. From these results, Chitlac-nAg seems to be a promising antibacterial and antibiofilm agent able to hinder plaque formation.

Characteristics of Streptococcus mutans genotypes and dental caries in children

This longitudinal cohort study evaluated the diversity, commonality, and stability of Streptococcus mutans genotypes associated with dental caries history. Sixty-seven 5- and 6-yr-old children, considered as being at high caries risk, had plaque collected from baseline through 36 months for S. mutans isolation and genotyping using repetitive extragenic palindromic-PCR (4,392 total isolates). Decayed, missing, or filled surfaces (dmfs (primary teeth)/DMFS (secondary teeth)) for each child were recorded at baseline. At baseline, 18 distinct genotypes were found among 911 S. mutans isolates from 67 children (diversity), and 13 genotypes were shared by at least two children (commonality). The number of genotypes per individual was positively associated with the proportion of decayed surfaces (p-ds) at baseline. Twenty-four of the 39 children who were available at follow-up visits maintained a predominant genotype for the follow-up periods (stability) and this was negatively associated with the p-ds. The observed diversity, commonality, and stability of S. mutans genotypes represent a pattern of dental caries epidemiology in this high-caries-risk community, which suggests that fewer decayed surfaces are significantly associated with lower diversity and higher stability of S. mutans genotypes.

Kaurenoic Acid from Aralia continentalis Inhibits Biofilm Formation of Streptococcus mutans

We isolated a single chemical compound from A. continentalis and identified it to be kaurenoic acid (KA) and investigated the influence of anticariogenic properties. Inhibitory effects of KA on cariogenic properties such as growth, acid production, biofilm formation, and the adherence of S. mutans were evaluated. Furthermore, real-time PCR analysis was performed to evaluate the influence of KA on the genetic expression of virulence factors. KA significantly inhibited the growth and acid production of S. mutans at 2–4 μg/mL and 4 μg/mL of KA, respectively. Furthermore, the adherence onto S-HAs was inhibited at 3-4 μg/mL of KA and biofilm formation was significantly inhibited when treated with 3 μg/mL KA and completely inhibited at 4 μg/mL. Also, the inhibitory effect of KA on biofilm formation was confirmed by SEM. In confocal laser scanning microscopy, bacterial viability gradually decreased by KA in a dose dependent manner. Real-time PCR analysis showed that the expressions of gtfB, gtfC, gbpB, spaP, brpA, relA, and vicR were significantly decreased in S. mutans when it was treated with KA. These results suggest that KA from A. continentalis may be a useful agent for inhibiting the cariogenic properties of S. mutans.

Mutans streptococci genetic strains in children with severe early childhood caries: follow-up study at one-year post-dental rehabilitation therapy

Background

Genotypic strains of cariogenic mutans streptococci (MS) may vary in important virulence properties. In previous published studies, we identified 39 MS strains from pediatric patients undergoing full-mouth dental rehabilitation, including the removal and/or repair of carious lesions and application of antimicrobial rinse and fluoride varnish.

Objectives

The objectives of this current 1-year follow-up study are to assess the variability of MS strains that occur at 1-year post-rehabilitation and characterize the xylitol-resistance properties of MS strains that predominate.

Methods

Plaque from five children with severe early childhood caries was collected 1-year post-rehabilitation. MS isolates were subjected to arbitrarily primed-polymerase chain reaction (AP-PCR) for identification of genetic strains and in vitro xylitol-inhibition experiments. To more precisely define strain distributions within each patient, we isolated large numbers of isolates per patient.

Results

MS strains diminished from several strains pre-rehabilitation, to one dominant strain at 1-year post-rehabilitation, with several new emergent strains. The majority of the clinical MS strains, as well as the Streptococcus mutans laboratory strains ATCC 25175 and 35668, were predicted to undergo 50% inhibition with 2.48–5.58% xylitol, with some clinical MS strains being significantly more resistant in vitro.

Conclusions

Our follow-up study using patients from the original cohort demonstrates that specific MS strains are dominant at 1-year post-dental rehabilitation. Most of the clinical MS strains are similar in xylitol resistance to the attenuated S. mutans ATCC control strains, with some strains being more resistant to xylitol in vitro.

Role of DNA base excision repair in the mutability and virulence of Streptococcus mutans

The oral pathogen, Streptococcus mutans, possesses inducible DNA repair defences for protection against pH fluctuations and production of reactive oxygen metabolites such as hydrogen peroxide (H(2) O(2) ), which are present in the oral cavity. DNA base excision repair (BER) has a critical role in genome maintenance by preventing the accumulation of mutations associated with environmental factors and normal products of cellular metabolism. In this study, we examined the consequences of compromising the DNA glycosylases (Fpg and MutY) and endonucleases (Smx and Smn) of the BER pathway and their relative role in adaptation and virulence. Enzymatic characterization of the BER system showed that it protects the organism against the effects of the highly mutagenic lesion, 7,8-dihydro-8-oxo-2'-deoxyguanine (8-oxo-dG). S. mutans strains lacking a functional Fpg, MutY or Smn showed elevated spontaneous mutation frequencies; and, these mutator phenotypes correlated with the ability of the strains to survive killing by acid and oxidative agents. In addition, in the Galleria mellonella virulence model, strains of S. mutans deficient in Fpg, MutY and Smn showed increased virulence as compared with the parent strain. Our results suggest that, for S. mutans, mutator phenotypes, due to loss of BER enzymes, may confer an advantage to virulence of the organism.

Horizontal transmission of Streptococcus mutans in schoolchildren

Objetive: The aim of this study was to analyze possible horizontal transmission patterns of S. mutans among 6-7-yr-old schoolchildren from the same class, identifying genotypes and their diversity and relationship with caries disease status. Study Design: Caries indexes and saliva mutans streptococci and lactobacilli counts were recorded in 42 schoolchildren. Mutans streptococci colonies were identified by means of biochemical tests and all S. mutans strains were genotyped by arbitrarily primed polymerase chain reaction. A child was considered free of S. mutans when it could not be isolated in 3 samples at 1-week intervals. Results: S. mutans was isolated in 30 schoolchildren: 20 having one genotype and 10 two genotypes. Higher mutans streptococci and caries index values were found in those with two genotypes. Five genotypes were isolated in more than 1 schoolchild and one of these was isolated in 3 schoolchildren. Our results suggest that horizontal transmission may take place. Conclusion: Schoolchildren aged 6-7 yrs may be the source of mutual transmission of S. mutans.

Key words:Streptococcus mutans, Horizontal transmission, AP-PCR, genotyping

Effect of mode of delivery and feeding practices on acquisition of oral Streptococcus mutans in infants

OBJECTIVE

It is a well-established fact that colonization of S. mutans occurs early in life. The purpose of this study is to determine the correlation between mode of delivery and other associating factors with colonization of oral S. mutans in the infants.

METHODS

The newborns were divided into two groups according to the mode of delivery: Infants who were delivered by either caesarean section (Group-C) or vaginally (Group-V). A total number of 60 mother-infant pairs were included and followed for 1 year. The swab samples were collected for the detection of S. mutans.

RESULTS

Analysis of data demonstrated the possible influence of prolonged bottle feeding (P = 0.007), socioeconomic status (P = 0.00030) and tasting of food by the mothers (P = 0.0065) on the initial acquisition of S. mutans in the oral cavity of infants.

CONCLUSION

The causes for initial acquisition of oral S. mutans in infants were postnatal factors like feeding and oral hygiene practices.

Bactericidal capacity of silver nanoparticles associated with Gantrez S-97 on Streptococcus mutans

Dental caries is a worldwide public health problem. S mutans plays an important role in the etiology of caries. There have been studies that showed the antimicrobial properties of silver nanoparticles are an effective agent to diminish S. mutans. The objective of this study was to evaluate the bactericidal and bacteriostatic effects of silver nanoparticles in addition to the Gantrez S-27 copolymer, on S mutans.

METHOD

We performed an in vitro experimental study using the liquid microdilution method in order to find the minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) with the subcultures obtained. The mixture was obtained by preparing 98 microg/mL of silver nanoparticles (10(3)mol) with Gantrez S-27 2%, in distilled water The readings were performed 24 hours after incubation and on 3 consecutive days. The results showed an average MTC of 6.12 microg /mL and MBC of 6.12 microg /mL.

CONCLUSION

The addition of Gantrez 2% to silver nanoparticles does not alter its antimicrobial effect.

Genetic diversity of plaque mutans streptococci with rep-PCR

Mutans streptococci (MS) are key organisms associated with the etiology of dental caries. Using probabilities that were tested by oversampling, we designed this study to determine the minimal number of MS isolates from an individual required to evaluate diversity of genotypes. MS isolates were genotyped by repetitive extragenic palindromic-polymerase chain-reaction (rep-PCR). Analysis of 20 isolates from individuals resulted in a mean of 1.6 and 2.4 genotypes in children (N = 12) and adults (N = 10), respectively. In a follow-up study, reducing the number of isolates to 7-10 resulted in a theoretical probability of up to 78% for detecting up to 4 genotypes. A mean of 1.5 genotypes was found in 35 children and 10 adults. These findings provide evidence for the design of studies of MS genotyping that can serve as a model for the analysis of genotypes within individuals.

Examination of the hdrRM regulon yields insight into the competence system of Streptococcus mutans

Previous studies have identified the hdrRM operon as a novel regulatory system induced by conditions of high cell density. Little is known about the genes under the control of this system, but a variety of important phenotypes are associated with either hdrR overexpression or mutation of hdrM. To characterize the regulatory function of the HdrRM system in Streptococcus mutans we used a microarray approach to compare the transcriptional profiles of an hdrR overexpression strain with an hdrM mutant. Both strains exhibited almost identical profiles, which included all of the known late competence genes as well as a variety of competence-induced bacteriocins. Through a combination of real-time reverse transcription-polymerase chain reaction (PCR), reporter gene analysis and random amplification of complementary DNA ends PCR, we confirmed the role of comX as a central intermediate regulator of numerous genes in the hdrRM regulon. Through these studies, we also identified novel comX-regulated genes required for natural competence. Taken together, our results suggest that the primary function of the HdrRM system is to regulate the late competence genes together with various bacteriocins. This occurs independently of the ComCDE system, even though both systems regulate nearly identical genes. This suggests that S. mutans has multiple parallel input sensory systems that control the same output response: the induction of natural competence and concurrent production of bacteriocins.

The Streptococcus mutans IrvR repressor is a CI-like regulator that functions through autocleavage and Clp-dependent proteolysis

Previous work has shown that irvR is required for the proper regulation of genetic competence and dextran-dependent aggregation due to its ability to repress the transcription regulator irvA. In this study, we determined the mechanism used to relieve the repression of irvA. We demonstrate that IrvR is a "LexA-like" protein with four conserved amino acid residues likely required for IrvR autocleavage activity. Furthermore, recombinant IrvR protein purified from Escherichia coli was competent to undergo autocleavage in vitro. Using several truncated IrvR constructs, we show that the amino acids adjacent to the autocleavage site are essential for relieving irvA repression and engaging the irvA-dependent regulatory pathway primarily through the ClpXP and ClpCP proteases. By extending the IrvR C terminus with an epitope derived from the autocleavage site, we were also able to create a constitutive Clp-dependent degradation of the full-length IrvR protein. This suggests that the derepression of irvA occurs through a two-step mechanism involving the initial autocleavage of IrvR and exposure of a proteolytic degradation sequence followed by Clp-dependent degradation of the IrvR DNA binding domain. Thus, irvA derepression is highly analogous to the genetic switch mechanism used to regulate lysogeny in bacteriophages.

Genotypic Diversity of Streptococcus mutans in Caries-Free and Caries-Active Preschool Children

Aim. The aim of the present paper was to evaluate the genotypic diversity of S. mutans in caries-free and caries-active preschool children in Brazil. Design. Twenty-eight preschool children were examined regarding caries experience by the dmft index. DNA from 280 isolates of S. mutans was extracted. S. mutans evaluated using to the PCR method, with primers for the glucosyltransferase gene. The genetic diversity of S. mutans isolates was analyzed by arbitrary primed-PCR (AP-PCR) reactions. The differences between the diversity genotypic and dmft/caries experience were evaluated by χ2 test and Spearman's correlation. Results. The Spearman correlation test showed a strong association between genotypic diversity and caries experience (r = 0.72; P < .001). There were more S. mutans genotypes in the group of preschool children with dental caries, compared with the caries-free group. Among the children with more than 1 genotype, 13 had dental caries (2 to 5 genotypes) and 4 were caries-free (only 2 genotypes). Conclusion. Our results support the previous findings of genetic diversity of S. mutans in preschool children being associated with dental caries. The investigation of such populations may be important for directing the development of programs for caries prevention worldwide.

Knowledge and attitude of parents or caretakers regarding transmissibility of caries disease

Dental caries is a transmissible infectious disease in which mutans streptococci are generally considered to be the main etiological agents. Although the transmissibility of dental caries is relatively well established in the literature, little is known whether information regarding this issue is correctly provided to the population. The present study aimed at evaluating, by means of a questionnaire, the knowledge and usual attitude of 640 parents and caretakers regarding the transmissibility of caries disease. Most interviewed adults did not know the concept of dental caries being an infectious and transmissible disease, and reported the habit of blowing and tasting food, sharing utensils and kissing the children on their mouth. 372 (58.1%) adults reported that their children had already been seen by a dentist, 264 (41.3%) answered that their children had never gone to a dentist, and 4 (0.6%) did not know. When the adults were asked whether their children had already had dental caries, 107 (16.7%) answered yes, 489 (76.4%) answered no, and 44 (6.9%) did not know. Taken together, these data reinforce the need to provide the population with some important information regarding the transmission of dental caries in order to facilitate a more comprehensive approach towards the prevention of the disease.

Streptococcal Infections

The streptococci are a large heterogeneous group of gram-positive spherically shaped bacteria widely distributed in nature. They include some of the most important agents of human disease as well as members of the normal human flora. Some streptococci have been associated mainly with disease in animals, while others have been domesticated and used for the culture of buttermilk, yogurt, and certain cheeses. Those known to cause human disease comprise two broad categories: First are the pyogenic streptococci, including the familiar β-hemolytic streptococci and the pneumococcus. These organisms are not generally part of the normal flora but cause acute, often severe, infections in normal hosts. Second are the more diverse enteric and oral streptococci, which are nearly always part of the normal flora and which are more frequently associated with opportunistic infections.