Prevalence of salivary Streptococcus mutans in mothers and in their preschool children

Summary. Objectives. To establish the prevalence and possible relationship of oral Streptococcusmutans colonization in mother–child pairs. Design and setting. An analytical cross‐sectional study was carried out at a well‐baby evaluation clinic held at the Public Dental Clinic, Varberg, Sweden. Sample and methods. Two hundred preschool children, 100 of which were 18 months old and the remaining 100 were 3 years old, and their mothers attended the clinic. All mothers were interviewed and their children’s medical history, oral hygiene routines and dietary habits established. All children were clinically examined. The presence and level of S. mutans was estimated in the mother–child pairs with the aid of the Strip mutans chair‐side test. Results. Nearly 50% of mothers exhibited high levels of salivary S. mutans, prevalence among the 18‐month‐ and 3‐year‐olds was 30% and 42%, respectively. A statistically significant (P < 0·01) mother–child relationship was found; a greater presence in mothers led to a higher number of children found harbouring the bacteria. Logistic regression analysis found that high maternal S. mutans levels (P < 0·001), daily sweet intake (P < 0·01) and sugary drinks in feeding bottles (P < 0·05) were significant factors for S. mutans colonization in children. Absence of daily toothbrushing and use of feeding bottles at night failed to fit into the model. Caries prevalence (initial and manifest decayed surfaces) was significantly related to S. mutans colonization (P < 0·01). Conclusion. The results support the concept of vertical transmission (mother–child), emphasizing the importance of the dietary component, and justifying a primary preventive approach with targeted action directed at mothers with high levels of S. mutans colonization.     

Establishment of Streptococcus mutans in infants induces decrease in the proportion of salivary α-haemolytic bacteria

International Journal of Paediatric Dentistry 2012; 22: 139–145 Objective. For paediatric dentists, an indicator to assess caries risk of infants is very important. Conventionally, the number and/or proportions of Streptococcus mutans have been employed as risk indicator; however, because such figures reflect the existing situation, they are not suitable for assessing caries risk of infants that have not yet been infected with S. mutans. Thus, we searched for an indicator for the establishment of S. mutans. Methods. To evaluate the changes caused by the establishment of S. mutans in the microbiota of the infant oral cavity, we monitored changes in the oral microbiota of two pre‐dentate infants over a 3‐year period and in a cross‐sectional study of 40 nursery school‐aged children by cultivation of saliva on nonselective blood agar, Mitis‐Salivarius agar, and Mitis‐Salivarius agar supplemented with bacitracin combined with identification of selected isolates. Results. Two longitudinal observations suggested that the establishment of S. mutans would induce a decrease in α‐haemolytic bacteria in the microbial population of the oral cavity. This suggestion was compensated with the results of cross‐sectional study, and it was revealed that the establishment of 10³ CFU/mL of mutans streptococci in saliva might be predicted by a microbiota comprising less than approximately 55% of α‐haemolytic. Conclusion. Decrease in the proportion of α‐haemolytic bacteria in saliva of infant was found to be applicable as an indicator to predict the establishment of S. mutans and to assess dental caries risk as a background for planning of dental care and treatment in the infants before infection with S. mutans.     

Collagen‐binding proteins of Streptococcus mutans and related streptococci

The ability of Streptococcus mutans to interact with collagen through the expression of collagen‐binding proteins (CBPs) bestows this oral pathogen with an alternative to the sucrose‐dependent mechanism of colonization classically attributed to caries development. Based on the abundance and distribution of collagen throughout the human body, stringent adherence to this molecule grants S. mutans with the opportunity to establish infection at different host sites. Surface proteins, such as SpaP, WapA, Cnm and Cbm, have been shown to bind collagen in vitro, and it has been suggested that these molecules play a role in colonization of oral and extra‐oral tissues. However, robust collagen binding is not achieved by all strains of S. mutans, particularly those that lack Cnm or Cbm. These observations merit careful dissection of the contribution from these different CBPs towards tissue colonization and virulence. In this review, we will discuss the current understanding of mechanisms used by S. mutans and related streptococci to colonize collagenous tissues, and the possible contribution of CBPs to infections in different sites of the host.     

Relationship of quantitative salivary levels of Streptococcus mutans and S. sobrinus in mothers to caries status and colonization of mutans streptococci in plaque in their 2.5-year-old children

Abstract – Objectives: The aim of this study was to assess the relationships of quantitative salivary levels of Streptococcus mutans and S. sobrinus in mothers with the colonization of mutans streptococci (MS) in plaque and caries status in their 2.5‐year‐old children. Furthermore, the dynamics of caries status in the children was evaluated in a 2‐year follow‐up survey. Methods: After oral examination of 54 mother‐and‐child pairs, the saliva samples from the mothers and the plaque samples from the children were collected. The levels (log DNA copies/ml saliva) of S. mutans and S. sobrinus were quantified using real‐time polymerase chain reaction (PCR) assays, while MS in the plaque samples were detected using a cultivation method. In addition, 50 of the 54 children participated in a 2‐year follow‐up survey of caries prevalence. Results: In the 2.5‐year‐old children, the percentage of dft‐positive subjects and mean number of dft were significantly higher in the MS(+) group when compared with the MS(?) group. Findings from the 2‐year follow‐up survey indicated that MS(+) subjects had a persistently higher mean number of dft at 4.5 years. The 2.5‐year‐old children were divided into three groups based on the quantitative levels of salivary S. mutans and S. sobrinus in their mothers: those whose mothers had low levels of S. mutans (<4 log DNA copies/ml) and S. sobrinus (<2) (group 1); those whose mothers had a high level of S. mutans (≥4) and low level of S. sobrinus (<2) (group 2); and those whose mothers had high levels of both (≥4 and ≥2, respectively) (group 3). Among the three groups, the percentages of MS(+) and dft‐positive children were highest in group 3 and lowest in group 1. Furthermore, multiple logistic regression analyses revealed that grouping the mothers based on salivary level of S. mutans and S. sobrinus was an efficient means to predict both MS colonization (OR = 2.96) and prevalence of dental caries (OR = 9.39) in children at 2.5 years of age. Conlusions: In the 54 mother‐and‐child pairs tested, the maternal salivary levels of S. mutans and S. sobrinus determined by real‐time PCR were significantly related to MS colonization in plaque as well as dental caries in their children at 2.5 years of age. Thus, determination of maternal levels of both organisms using the present cut‐off values is proposed as an efficient method to indicate the risks of maternal transmission of MS and childhood dental caries.     

Antibacterial activity of polysaccharide gel extract from fruit rinds of Durio zibethinus Murr. against oral pathogenic bacteria

Aim: The polysaccharide gel (PG) extract from durian fruit rinds (Durio zibethinus Murr. “Monthong”) is a pectic polysaccharide with antibacterial activity. This study aimed to investigate the in vitro antibacterial activity of PG against oral pathogens, Streptococcus mutans (S. mutans) and Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans). Methods: The inhibitory activity of PG at 50, 100, and 150 mg/mL against S. mutans (American Tissue Culture Collection 25175) and A. actinomycetemcomitans (American Tissue Culture Collection 43718) was determined after 1‐ and 5‐min exposure by broth macrodilution susceptibility test and scanning electron microscopy. Normal saline or culture broth medium and 0.1% chlorhexidine were used as negative and positive controls, respectively. Results: For 1‐min exposure, 150 mg/mL PG or 0.1% chlorhexidine significantly possessed bactericidal activity against both tested bacteria (P = 0.037), while PG at 100 mg/mL possessed significant bactericidal activity against S. mutans (P = 0.037) and inhibitory activity against A. actinomycetemcomitans (P = 0.05). Blebs, irregular‐shaped cells, and disrupted cells were found in bacteria treated with either 0.1% chlorhexidine or 50–150 mg/mL PG under scanning electron microscopy. Conclusion: The bactericidal activity of PG at 150 mg/mL against oral bacteria at 1‐min exposure suggests its possibility to be used as a natural antibacterial ingredient in oral hygiene products.     

Detection of oral streptococci with collagen‐binding properties in saliva specimens from mothers and their children

International Journal of Paediatric Dentistry 2010; 20: 254–260 Background. Approximately 10–20% of Streptococcus mutans strains have been reported to possess collagen‐binding properties, whereas other species in the oral cavity with those properties remain to be elucidated. Aim. To identify strains with collagen‐binding properties and analyse their characteristics in comparison with S. mutans. Design. A total of 110 expectorated saliva specimens were collected from 55 pairs of mothers and their children. Bacterial strains with collagen‐binding properties were isolated and the species specified. In addition, strains with collagen‐binding properties isolated from mother–child pairs were analysed using molecular biological approaches. Results. The detection frequency of strains with collagen‐binding properties was shown to be 40.9%, among which S. salivarius was the most frequently detected, followed by S. mutans. The collagen‐binding activity of the S. mutans group was the highest, followed by S. salivarius. In addition, S. mutans and S. salivarius strains from 3 and 1 mother–child pairs, respectively, were shown to be the same clones. Conclusions. Our results indicate that S. mutans and S. salivarius are major species with collagen‐binding properties in the oral cavity, and that strains with such properties may be related to mother–child transmission.     

Salivary proteins promote proteolytic activity in Streptococcus mitis biovar 2 and Streptococcus mutans

A major function of the salivary pellicle on oral surfaces is to promote colonization of the commensal microbiota by providing binding sites for adherence. Streptococcus mitis is an early colonizer of the oral cavity whereas Streptococcus mutans represents a later colonizer. To survive and grow, oral bacteria produce enzymes, proteases and glycosidases, which allow them to exploit salivary proteins as a nutrient source. In this study, adherence and proteolytic activity of S. mitis biovar 2 and S. mutans were investigated in a flow‐cell model in the presence of different populations of surface‐associated salivary proteins. Streptococcus mitis biovar 2 adhered well to surfaces coated with both a MUC5B‐enriched fraction and a pool of low‐density proteins containing MUC7, amylase, cystatin, gp340, immunoglobulin A, lactoferrin, lysozyme and statherin, whereas adherence of S. mutans to these proteins was poor. In environments of MUC5B or the low‐density proteins, both S. mitis biovar 2 and S. mutans showed high levels of proteolytic activity. For S. mitis in the MUC5B environment, most of this activity may be attributable to contact with the molecules in the fluid phase although activity was also enhanced by adherence to surface‐associated MUC5B. These data suggest that although they differ in their capacity to adhere to surface‐associated salivary proteins, in the natural environment exploitation of saliva as a nutrient source can contribute to survival and colonization of the oral cavity by both S. mitis biovar 2 and S. mutans.     

Genotypic and phenotypic analysis of Streptococcus mutans from different oral cavity sites of caries‐free and caries‐active children

Introduction: Streptococcus mutans exhibits extensive genotypic diversity, but the role of this variation is poorly understood. This study aimed to determine the number and distribution of genotypes of S. mutans isolated from caries‐active and caries‐free children and to evaluate some of their phenotypic traits. Methods: Stimulated saliva, tongue surface and biofilms over sound and carious teeth surfaces were sampled from 10 caries‐free and 11 caries‐active children aged 5–8 years. A total of 339 isolates of S. mutans were genotyped by arbitrarily primed polymerase chain reaction using OPA2 primer. One isolate from each genotype was tested for its acid susceptibility and its ability to form a biofilm. Results: Fifty‐one distinct genotypes were determined, one to three genotypes in each oral sample. A single genotype was detected in seven children, whereas the remaining 14 children exhibited two to seven genotypes. There were no significant differences in the number of genotypes detected in caries‐free and caries‐active children. No correlation was observed between the number of genotypes and the mutans streptococci salivary levels. Five of the six high biofilm‐forming genotypes were obtained from caries‐active children, although the differences in biofilm formation between isolates from caries‐free and caries‐active children were not statistically significant. Genotypes with low susceptibility to acid challenge were statistically more frequent among isolates from caries‐active children than among those from caries‐free children. Conclusion: The present data suggested that there were differences in the distribution of genotypes of S. mutans according to the oral site and that S. mutans populations differ in their acid susceptibility and ability to form biofilms, factors allowing their colonization of sucrose‐rich environments.     

Influence of VicRK and CovR on the interactions of Streptococcus mutans with phagocytes

Oral Diseases (2012) 18 , 485–493 Objective: Streptococcus mutans are members of the oral microbiota that are implicated in dental caries and infective endocarditis. To adapt to environmental stresses encountered during host colonization, these bacteria employ two‐component regulatory systems, which modulate global changes in gene expression. These include the systems VicRK and CovR. In this study, we investigate the influence of VicRK and CovR in S. mutans interactions with mononuclear and polymorphonuclear (PMN) phagocytes. Methods: Patterns of S. mutans uptake by murine macrophages were determined in strains, which differ in the production of proteins regulated by VicRK and CovR. Bacterial uptake by murine macrophages and by PMN in human blood was analyzed in vicK and covR knockout mutants obtained in strains UA159 and LT11. Results: Inactivation of covR did not affect uptake by macrophages, while vicK inactivation transiently reduced uptake only in LT11 (P < 0.05). In the two strains, inactivation of vicK and covR impaired uptake by PMN for a period of 1 h or more (P < 0.01–0.05). Mutant complementation with vicK or covR restored the PMN uptake phenotypes. Conclusion: This study indicates that VicRK and CovR regulate functions that influence bacterial susceptibility to phagocytosis, suggesting a novel role for these systems in the virulence of S. mutans.     

Low salivary IgA activity to cell‐surface antigens of mutans streptococci related to HLA‐DRB1*04

Background/aims: Mutans streptococci are found in almost all individuals, though there are large differences in colonization levels between individuals. These differences are not readily explained, though several factors are believed to influence the colonization. One factor is the immune response to mutans streptococci, mainly provided by salivary immunoglobulin A (IgA). In a previous study, differences in salivary IgA reactions to oral streptococci were observed between human leukocyte antigen (HLA)‐DR4‐positive and DR4‐negative individuals. A lower salivary IgA activity to Streptococcus mutans in particular was most pronounced for two DR4 subgroups, DRB1*0401 and *0404. The main purpose of this study was to further investigate, in a larger study group, the salivary IgA activity to antigens of three oral streptococci in relation to different HLA‐DRB1*04 alleles. Methods: Stimulated saliva was collected from 58 HLA‐DRB1*04‐positive individuals. Whole cell antigen extracts from S. mutans, Streptococcus sobrinus and Streptococcus parasanguis and the streptococcal antigen (SA) I/II were separated in SDS‐PAGE, transblotted and detected with diluted saliva (Western blot), and analyzed in a computer program. All distinct immunoblot bands over 100 kDa were recorded and compared in relation to DRB1*04. Results: The immunoblots revealed lower salivary IgA reactions to S. mutans, S. sobrinus and SA I/II, but not to S. parasanguis, for the DRB1*0401‐ and *0404‐positive individuals compared to other DRB1*04 types. For the *0401 subgroup there was a significant association with a lower IgA response to S. mutans. Conclusion: The results confirm earlier observations and may also support previous demonstrated association between colonization by mutans streptococci and the serologically defined HLA‐DR4.     

Streptococcus mutans strains recovered from caries-active or caries-free individuals differ in sensitivity to host antimicrobial peptides

Antimicrobial peptides (AMPs) are among the repertoire of host innate immune defenses. In the oral cavity, several AMPs are present in saliva and have antimicrobial activities against oral bacteria, including Streptococcus mutans, a primary etiological agent of dental caries. In this study, we hypothesized that unique S. mutans strains, as determined by DNA fingerprinting from sixty 13‐year‐old subjects with or without experience of caries, would have different susceptibilities to α‐defensins‐1–3 (HNP‐1–3), β‐defensins‐2–3 (HBD‐2–3) and LL‐37. The salivary levels of these peptides in subjects were also measured by enzyme‐linked immunosorbent assays. We found that S. mutans strains from children with active caries showed greater resistance to salivary HNP‐1–2, HBD‐2–3 and LL‐37 at varying concentrations than those from caries‐free subjects. In addition, combinations of these peptides increased their antimicrobial activity against S. mutans either additively or synergistically. The salivary levels of these peptides were highly variable among subjects with no correlation to host caries experience. However, the levels of a number of these peptides in saliva appeared to be positively correlated within an individual. Our findings suggest that the relative ability of S. mutans to resist host salivary AMPs may be considered a potential virulence factor for this species such that S. mutans strains that are more resistant to these peptides may have an ecological advantage to preferentially colonize within dental plaque and increase the risk of dental caries.     

The mutacins of Streptococcus mutans: regulation and ecology

Streptococcus mutans is generally recognized as a causative agent of human dental caries. The production of mutacins (bacteriocins) by S. mutans is considered to be an important factor in the colonization and establishment of S. mutans in the dental biofilm. Two types of mutacins have been characterized: the lantibiotics and the non‐lantibiotics. The lantibiotics generally have a wider spectrum of activity than the non‐lantibiotics, which make them attractive targets for development into new antimicrobial modalities. The non‐lantibiotics are much more prevalent among strains of S. mutans and play a significant role in both community‐level and population‐level interactions in the dental biofilm. These interactions are directly mediated through the ComCDE two‐component system and the newly characterized LytTR Regulation Systems HdrRM and BrsRM. These systems coordinate natural competence development and mutacin production as a means to acquire transforming DNA either by killing closely related streptococcal species in the vicinity of S. mutans, or through an altruistic suicide mechanism among a subpopulation of competent cells within the S. mutans community. As more S. mutans strains are sequenced, it is anticipated that additional mutacins with novel functions will be discovered, which may yield further insights into the ecological role of mutacins within the oral biofilm.     

Genotypic diversity of Streptococcus mutans and Streptococcus sobrinus in 3-4-year-old children with severe caries or without caries

International Journal of Paediatric Dentistry 2011; 21: 422–431 Background. The genotypic diversity of both Streptococcus mutans and Streptococcus sobrinus in children with different caries experience remains unclear. Aim. To investigate the genotypic diversity of S. mutans and S. sobrinus in children with severe early childhood caries (SECC) and in caries‐free (CF) children. Methods. Stimulated saliva of 87 SECC and 91 CF children aged 3–4 years was collected and submitted to cultivation, and MS colonies were enumerated. The genomic fingerprint analysis of S. mutans and S. sobrinus was carried out using AP‐PCR. Results. One to five genotypes of S. mutans were colonized in an oral cavity of SECC and CF children; 85.5% SECC children and 57.9% CF children harboured more than one genotype of S. mutans. One to three genotypes of S. sobrinus were detected from each SECC child; 31.25% SECC children harboured more than one genotype of S. sobrinus. And one genotype was colonized in each CF child. S. mutans isolates from different individuals displayed distinctive DNA fingerprints. Conclusions. DNA fingerprints of S. mutans and S. sobrinus isolates from 3‐ to 4‐year‐old children displayed genetic polymorphism, and S. mutans has greater genetic diversity than S. sobrinus. SECC children harboured more genotypes of S. mutans and S. sobrinus than CF children.     

PCR detection of Streptococcus mutans and Streptococcus sobrinus in plaque samples from Mongolian mother-child pairs

Early childhood caries results in a considerable burden of pain and suffering as well as poorer general health. Streptococcus mutans (serotypes c, e and f ) and Streptococcus sobrinus (serotype d and g) are the species closely associated with dental caries. The exact age at which their colonization occurs in children is controversial. The objective of this study was to detect S. mutans and S. sobrinus in plaque samples of Mongolian mother-child pairs by PCR and to compare their presence with the caries status. Dental examination and caries risk assessment using the Cariostat^® carried out on 320 children aged 6–30 months and their mothers. The presence of S. mutans and S. sobrinus was checked by PCR. The caries prevalence and DEFT scores of mothers enrolled in the present study were 98% and 11.5±0.7, respectively. In children, the prevalence and deft scores of the 6–18-month-olds were 29% and 1.3±0.2 while those of the 19–30-month-olds were 59% and 3.4±0.4 correspondingly. Twenty nine percent of the 6–18-months old children of high-risk mothers and 53.1% of the 19–30-months old children of high-risk mothers had high caries risk (P<0.001). There was a statistically significant correlation between caries risk of 19–30 month-old children and their mothers (P<0.001). In mothers, the prevalence of S. mutans and S. sobrinus was 79% and 33%, respectively; 54% harbored S. mutans alone, 8% harbored S. sobrinus alone, 25% harbored both strains. In children, 45% were positive for S. mutans alone, 9% were positive for S. sobrinus alone, 18% were positive for both strains. Either or both strains were detected in 67.3% of 6–18-months old children and 76.5% of 19–30-months old children. In conclusion, our results showed that S. mutans and/or S. sobrinus first colonized infants’ teeth from 6–18 months, and the colonization increased with increasing age, so that by 30 months of age, 76.5% of children harbored the bacteria.     

Mutacin production in Streptococcus mutans genotypes isolated from caries‐affected and caries‐free individuals

Relationships between genetic diversity and mutacin production in Streptococcus mutans were evaluated in 319 clinical isolates from eight caries‐affected and eight caries‐free individuals. The isolates were submitted to mutacin typing and AP‐PCR (arbitrarily primed polymerase chain reaction) assay. The mutacin production was detected for 12 Streptococcus sp. indicator strains. Results showed significant variations in the mutacin production profiles and the inhibitory spectra of both groups. A possible association was seen between mutacin activity and the distinct patterns of Streptococcus sp. colonization in the two groups. Genotyping by AP‐PCR using the primers OPA‐02 and OPA‐13 revealed 101 distinct genotypes against 48 phenotypes identified by mutacin typing. No correlation was observed between the inhibitory spectra of mutacin and genotypic similarities based on AP‐PCR analyses. According to our results, strains of the same S. mutans genotype showed different mutacin profiles, suggesting a high degree of interstrain diversity. In conclusion, mutacin production seems to be of clinical importance in the colonization of S. mutans and is highly diversified in the S. mutans species.     

Salivary IgA antibody responses to Streptococcus mitis and Streptococcus mutans in preterm and fullterm newborn children

ObjectivesThe intensities and specificities of salivary IgA antibody responses to antigens of Streptococcus mutans, the main pathogen of dental caries, may influence colonization by these organisms during the first 1.5 year of life. Thus, the ontogeny of salivary IgA responses to oral colonizers continues to warrant investigation, especially with regard to the influence of birth conditions, e.g. prematurity, on the ability of children to efficiently respond to oral microorganisms. In this study, we characterised the salivary antibody responses to two bacterial species which are prototypes of pioneer and pathogenic microorganisms of the oral cavity (Streptococcus mitis and Streptococcus mutans, respectively) in fullterm (FT) and preterm (PT) newborn children.MethodsSalivas from 123 infants (70 FT and 53 PT) were collected during the first 10 h after birth and levels of IgA and IgM antibodies and the presence of S. mutans and S. mitis were analysed respectively by ELISA and by chequerboard DNA–DNA hybridization. Two subgroups of 24 FT and 24 PT children were compared with respect to patterns of antibody specificities against S. mutans and S. mitis antigens, using Western blot assays. Cross-adsorption of 10 infant's saliva was tested to S. mitis, S. mutans and Enterococcus faecalis antigens.ResultsSalivary levels of IgA at birth were 2.5-fold higher in FT than in PT children (Mann–Whitney; P < 0.05). Salivary IgA antibodies reactive with several antigens of S. mitis and S. mutans were detected at birth in children with undetectable levels of those bacteria. Adsorption of infant saliva with cells of S. mutans produced a reduction of antibodies recognizing S. mitis antigens in half of the neonates. The diversity and intensity of IgA responses were lower in PT compared to FT children, although those differences were not significant.ConclusionThese data provide evidence that children have salivary IgA antibodies shortly after birth, which might influence the establishment of the oral microbiota, and that the levels of salivary antibody might be related to prematurity.     

Salivary antimicrobial proteins associate with age‐related changes in streptococcal composition in dental plaque

Secretion of antimicrobial proteins (AMPs) and salivary antibodies can modify biofilm formation at host body surfaces. In adolescents, associations have been reported between dental caries and salivary AMPs. AMPs demonstrate direct antimicrobial effects at high concentrations, and at lower more physiological concentrations they mediate changes in host cell defenses, which may alter the local environment and indirectly shape local biofilm formation. The expression of salivary AMPs in preschool children, at an age when the oral bacteria are known to change, has not been investigated. We sought to investigate salivary AMP expression in the context of previously well‐documented changes in the oral cavities of this age group including salivary immunoglobulin A (IgA), oral bacteria and dental caries. Dental plaque and saliva were collected from 57 children aged 12–24 months at baseline, of whom 23 children were followed‐up at 3 years of age. At each time, saliva was assessed for LL37, human neutrophil peptides 1–3, calprotectin, lactoferrin, salivary IgA, total plaque bacteria and Streptococcus mutans. Over time, concentrations of AMPs, S. mutans and bacteria‐specific salivary IgA increased. Caries experience was also recorded when children were 3 years old. Concentrations of AMPs were highest in the saliva of 3‐year‐old children with the greatest burden of S. mutans. These data suggest that salivary AMPs are variable over time and between individuals, and are linked with bacterial colonization. At follow up, the majority of children remained caries free. Larger longitudinal studies are required to confirm whether salivary AMP levels are predictive of caries and whether their modulation offers therapeutic benefit.     

Phenotypic characterization of the foldase homologue PrsA in Streptococcus mutans

Streptococcus mutans is generally considered to be the principal etiological agent for dental caries. Many of the proteins necessary for its colonization of the oral cavity and pathogenesis are exported to the cell surface or the extracellular matrix, a process that requires the assistance of the export machineries. Bioinformatic analysis revealed that the S. mutans genome contains a prsA gene, whose counterparts in other gram‐positive bacteria, including Bacillus and Lactococcus, encode functions involved in protein post‐export. In this study, we constructed a PrsA‐deficient derivative of S. mutans and demonstrated that the prsA mutant displayed an altered cell wall/membrane protein profile as well as cell‐surface‐related phenotypes, including auto‐aggregation, increased surface hydrophobicity and abnormal biofilm formation. Further analysis revealed that the disruption of the prsA gene resulted in reduced insoluble glucan production by cell surface localized glucosyltransferases, and mutacin as well as cell surface‐display of a heterologous expressed GFP fusion to the cell surface protein SpaP. Our study suggested that PrsA in S. mutans encodes functions similar to those identified in Bacillus, and so is likely to be involved in protein post‐export.     

Novel method for the depletion of cariogenic bacteria using dextranomer microspheres

Streptococcus mutans is recognized as one of the key contributors to the dysbiotic state that results in dental caries. Existing treatment strategies reduce the incidence of tooth decay, but they also eliminate both the cariogenic and beneficial microbes. Here we introduce a novel treatment alternative using Sephadex, cross‐linked dextranomer microspheres (DMs), typically used for gel filtration chromatography. In addition DM beads can be used for affinity purification of glucosyltransferases (GTFs) from S. mutans. In this study we take advantage of the native pathogenic mechanisms used by S. mutans to adhere, form a biofilm and induce dental caries through the expression of surface‐associated GTFs. We demonstrate that planktonic and biofilm‐grown (adhered to hydroxyapatite‐coated pegs to mimic the tooth surface) S. mutans, specifically and competitively attach to DMs. Further investigation demonstrated that DMs are a specific affinity resin for S. mutans and other cariogenic/pathogenic oral streptococci, whereas other commensal and probiotic strains failed to readily adhere to DMs. Using antimicrobial cargo loaded into the DM lumen, we demonstrate that when in co‐culture with non‐binding to even modestly binding commensal species, S. mutans was selectively killed. This proof of concept study introduces a novel means to safely and effectively reduce the pool of S. mutans and other pathogenic streptococci in the oral cavity with limited disturbance of the necessary commensal (healthy) microbiota when compared with current oral healthcare products.