Genetic Diversity and Evidence for Transmission of Streptococcus mutans by DiversiLab rep-PCR

Intraspecies interactions of Streptococcus mutans impact biofilm architecture and virulence determinants in childhood dental caries

Early childhood dental caries (ECC) is the most common chronic disease among children, especially among low socioeconomic populations. Streptococcus mutans is most frequently associated with initiation of ECC. Although many studies report children with multiple S. mutans strains (i.e., genotypes) have greater odds of developing ECC, studies investigating intraspecies interactions in dental caries are lacking. This study investigates the impact of intraspecies interactions on cariogenic and fitness traits of clinical S. mutans isolates using in vitro and in vivo approaches. Association analysis evaluated if presence of multiple S. mutans genotypes within the first year of colonization was associated with caries. Initially, clinical S. mutans isolates from 10 children were evaluated. S. mutans strains (G09 and G18, most prevalent) isolated from one child were used for subsequent analysis. Biofilm analysis was performed for single and mixed cultures to assess cariogenic traits, including biofilm biomass, intra-polysaccharide, pH, and glucan. Confocal laser scanning microscopy (CLSM) and time-lapse imaging were used to evaluate spatial and temporal biofilm dynamics, respectively. A Drosophila model was used to assess colonization in vivo. Results showed the mean biofilm pH was significantly lower in co-cultured biofilms versus monoculture. Doubling of S. mutans biofilms was observed by CLSM and in vivo colonization in Drosophila for co-cultured S. mutans. Individual strains occupied specific domains in co-culture and G09 contributed most to increased co-culture biofilm thickness and colonization in Drosophila. Biofilm formation and acid production displayed distinct signatures in time-lapsed experiments. This study illuminates that intraspecies interactions of S. mutans significantly impacts biofilm acidity, architecture, and colonization.IMPORTANCEThis study sheds light on the complex dynamics of a key contributor to early childhood dental caries (ECC) by exploring intraspecies interactions of different S. mutans strains and their impact on cariogenic traits. Utilizing clinical isolates from children with ECC, the research highlights significant differences in biofilm architecture and acid production in mixed versus single genotype cultures. The findings reveal that co-cultured S. mutans strains exhibit increased cell density and acidity, with individual strains occupying distinct domains. These insights, enhanced by use of time-lapsed confocal laser scanning microscopy and a Drosophila model, offer a deeper understanding of ECC pathogenesis and potential avenues for targeted interventions.

Plasmalogen, a glycerophospholipid crucial for Streptococcus mutans acid tolerance and colonization

Plasmalogen is a specific glycerophospholipid present in both animal and bacterial organisms. It plays a crucial function in eukaryotic cellular processes and is closely related to several human diseases, including neurological disorders and cancers. Nonetheless, the precise biological role of plasmalogen in bacteria is not well understood. In this study, we identified SMU_438c as the enzyme responsible for plasmalogen production in Streptococcus mutans under anaerobic conditions. The heterologous expression of SMU_438c in a plasmalogen-negative strain, Streptococcus sanguinis, resulted in the production of plasmalogen, indicating that this enzyme is sufficient for plasmalogen production. Additionally, the plasmalogen-deficient S. mutans exhibited significantly lower acid tolerance and diminished its colonization in Drosophila flies compared to the wild-type strain and complemented strain. In summary, our data suggest that plasmalogen plays a vital role in bacterial stress tolerance and in vivo colonization.

IMPORTANCE

This study sheds light on the biological role of plasmalogen, a specific glycerophospholipid, in bacteria, particularly in Streptococcus mutans. Plasmalogens are known for their significant roles in eukaryotic cells and have been linked to human diseases like neurological disorders and cancers. The enzyme SMU_438c, identified as essential for plasmalogen production under anaerobic conditions, was crucial for acid tolerance and in vivo colonization in Drosophila by S. mutans, underscoring its importance in bacterial stress response and colonization. These findings bridge the knowledge gap in bacterial physiology, highlighting plasmalogen's role in microbial survival and offering potential insights into microbial pathogenesis and host-microbe interactions.

Intraspecies interactions of Streptococcus mutans impact biofilm architecture and virulence determinants in childhood dental caries

Early childhood dental caries (ECC) is the most common chronic disease among children with a heavy disease burden among low socioeconomic populations. Streptococcus mutans is most frequently associated with initiation of ECC. Many studies report children with multiple S. mutans strains (i.e., genotypes) having greater odds of developing ECC, studies investigating intraspecies interactions in dental caries are lacking. In this study, the impact of intraspecies interactions on cariogenic and fitness traits of clinical S. mutans isolates are investigated using in-vitro and in-vivo approaches. Initially clinical S. mutans isolates of 10 children from a longitudinal epidemiological study were evaluated. S. mutans strains (G09 and G18, most prevalent) isolated from one child were used for subsequent analysis. Association analysis was used to determine if presence of multiple S. mutans genotypes within the first-year of colonization was associated with caries. Biofilm analysis was performed for single and mixed cultures to assess cariogenic traits, including biofilm biomass, intra-polysaccharide, pH, and glucan. Confocal Laser Scanning Microscopy (CLSM) and time-lapse imaging were used to evaluate spatial and temporal biofilm dynamics, respectively. A Drosophila model was used to assess colonization in-vivo. Mean biofilm pH was significantly lower in co-cultured biofilms as compared with monoculture biofilms. Doubling of S. mutans in-vitro biofilms was observed by CLSM and in-vivo colonization in Drosophila for co-cultured S. mutans. Individual strains occupied specific domains in co-culture and G09 contributed most to increased co-culture biofilm thickness and colonization in Drosophila. Biofilm formation and acid production displayed distinct signatures in time-lapsed experiments.

Assessment of Diversity and Fidelity of Transmission of Streptococcus mutans Genotypes in American Indian and Southeast Iowa Mother-Child Dyads

Early childhood caries (ECC) is a common chronic infectious disease of childhood with a complex etiology and many contributing risk factors. Its prevalence is greater in certain racial and ethnic minority groups and populations with low socioeconomic status. Among the species of bacteria that contribute to the progression of dental caries, Streptococcus mutans (SM) has long been considered a primary etiological agent of the disease. We report here on the genotypic diversity, commonality, and fidelity of mother-child transmission of S. mutans in mother-child dyads in two high-risk populations.

Methods

Thirty-eight mother-child dyads from a Southeast Iowa population and 40 dyads from a Northern Plains American Indian Tribe were selected for a comparison of S. mutans genotype profiles within and between populations. S. mutans was isolated from whole mouth plaque samples collected from each subject. DNA was extracted and AP-PCR using OPA2 primer was performed. Amplified DNA was electrophoresed and images of the resulting patterns were compared via GelCompar®IIv6.5 software.

Results

Thirty unique S. mutans genotypes were identified from the 1,638 S. mutans isolates analyzed. Fifteen genotypes (50%) were seen in both cohorts, while 11 were unique to the American Indian (AI) cohort and 4 were unique to the Southeast Iowa (SEI) population. Within the AI cohort, 61.5% (16/26) of the S. mutans genotypes identified were seen in ≥2 individuals and 14 of the 26 (53.8%) were seen in ≥2 dyads. In the SEI cohort, 78.9% (15/19) of the S. mutans genotypes identified were seen in ≥2 individuals and 13 of the 19 (68.4%) were present in ≥2 dyads. Fifty-seven percent of AI children and 23% of SEI children displayed fidelity of mother-child transmission of ≥1 S. mutans genotype.

Conclusion

In comparing the populations, we observed large variation in genotypic diversity and fidelity of mother-child transmission, while the amount of commonality seen in both cohorts was similarly high in both groups. This study furthers our understanding of the genotypic diversity of S. mutans in both of these populations and provides a basis for further comparison to other populations at greater risk for developing ECC.

A Core Genome Multilocus Sequence Typing Scheme for Streptococcus mutans

Streptococcus mutans is one of the primary pathogens responsible for the development of dental caries. Recent whole-genome sequencing (WGS)-based core genome multilocus sequence typing (cgMLST) approaches have been employed in epidemiological studies of specific human pathogens. However, this approach has not been reported in studies of S. mutans Here, we therefore developed a cgMLST scheme for S. mutans We surveyed 199 available S. mutans genomes as a means of identifying cgMLST targets, developing a scheme that incorporated 594 targets from the S. mutans UA159 reference genome. Sixty-eight sequence types (STs) were identified in this cgMLST scheme (cgSTs) in 80 S. mutans isolates from 40 children that were sequenced in this study, compared to 35 STs identified by multilocus sequence typing (MLST). Fifty-six cgSTs (82.35%) were associated with a single isolate based on our cgMLST scheme, which is significantly higher than in the MLST scheme (11.43%). In addition, 58.06% of all MLST profiles with ≥2 isolates were further differentiated by our cgMLST scheme. Topological analyses of the maximum likelihood phylogenetic trees revealed that our cgMLST scheme was more reliable than the MLST scheme. A minimum spanning tree of 145 S. mutans isolates from 10 countries developed based upon the cgMLST scheme highlighted the diverse population structure of S. mutans This cgMLST scheme thus offers a new molecular typing method suitable for evaluating the epidemiological distribution of this pathogen and has the potential to serve as a benchmark for future global studies of the epidemiological nature of dental caries.IMPORTANCE Streptococcus mutans is regarded as a major pathogen responsible for the onset of dental caries. S. mutans can transmit among people, especially within families. In this study, we established a new epidemiological approach to S. mutans classification. This approach can effectively differentiate among closely related isolates and offers superior reliability relative to that of the traditional MLST molecular typing method. As such, it has the potential to better support effective public health strategies centered around this bacterium that are aimed at preventing and treating dental caries.

Overestimation of Early Childhood Caries Using the dmfs Index

Purpose: The preferred epidemiological caries assessment method is the decayed, missing, and filled surfaces (dmfs) score, which records all crowned/missing primary teeth's surfaces as carious. The purpose of this study was to evaluate the dmfs score's accuracy in capturing caries-affected (versus treated) surfaces of crowned/extracted teeth. Methods: A high-caries risk cohort of children, eight to 18 months old at baseline, were recruited from a nonfluoridated, rural, minority, and low-income community. Oral examinations occurred every 12 months for five years, identifying children with at least one caries-related crown/extraction (N equals 45). Observed scoring counted all crowned/extracted surfaces as carious. Private dentists' clinical records were also reviewed to determine how many surfaces were carious at crown/extraction appointments (53 actual scores for n equals 19). Differences in actual and observed scoring were evaluated (sign test; α equals 0.05 with two-tailed P-values). Results: Most children in the study group had more than one crown/extraction. Actual scoring revealed two to three fewer carious surfaces per tooth than observed scoring; cumulatively, observed scoring added two to 27 more surface counts per participant (P<0.001). Conclusions: Observed scoring exaggerated early childhood caries burdens when crowns/extractions were prevalent. Modified dmfs scoring, individualized or population-corrected crown/extraction counts, could more accurately estimate disease.

Caries-Associated Biosynthetic Gene Clusters in Streptococcus mutans

Early childhood caries (ECC) is a chronic disease affecting the oral health of children globally. This disease is multifactorial, but a primary factor is cariogenic microorganisms such as Streptococcus mutans. Biosynthetic gene clusters (BGCs) encode small molecules with diverse biological activities that influence the development of many microbial diseases, including caries. The purpose of this study was to identify BGCs in S. mutans from a high-caries risk study population using whole-genome sequencing and assess their association with ECC. Forty representative S. mutans isolates were selected for genome sequencing from a large-scale epidemiological study of oral microbiology and dental caries in children from a localized Alabama population. A total of 252 BGCs were identified using the antiSMASH BGC-mining tool. Three types of BGCs identified herein-butyrolactone-like, ladderane-like, and butyrolactone-ladderane-like hybrid (BL-BGC)-have not been reported in S. mutans. These 3 BGCs were cross-referenced against public transcriptomics data, and were found to be highly expressed in caries subjects. Furthermore, based on a polymerase chain reaction screening for core BL genes, 93% of children with BL-BGC had ECC. The role of BL-BGC was further investigated by examining cariogenic traits and strain fitness in a deletion mutant using in vitro biofilm models. Deletion of the BL-BGC significantly increased biofilm pH as compared to the parent strain, while other virulence and fitness properties remained unchanged. Intriguingly, BL-BGC containing strains produced more acid, a key cariogenic feature, and less biofilm than the model cariogenic strain S. mutans UA159, suggesting the importance of this BL-BGC in S. mutans-mediated cariogenesity. The structure of any BL-BGC derived metabolites, their functions, and mechanistic connection with acid production remain to be elucidated. Nevertheless, this study is the first to report the clinical significance of a BL-BGC in S. mutans. This study also highlights pangenomic diversity, which is likely to affect phenotype and virulence.

Advanced DNA fingerprint genotyping based on a model developed from real chip electrophoresis data

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Mapping chip electrophoresis distortion based on real data measurement.

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Determining the transformation function for the adaptive correction of band size deviation.

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Improving the ability to distinguish closely related DNA fingerprints.

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Using hierarchical clustering to adjust the global band position.

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Genotyping all DNA fingerprints from multiple runs at once.

Large-scale comparative studies of DNA fingerprints prefer automated chip capillary electrophoresis over conventional gel planar electrophoresis due to the higher precision of the digitalization process. However, the determination of band sizes is still limited by the device resolution and sizing accuracy. Band matching, therefore, remains the key step in DNA fingerprint analysis. Most current methods evaluate only the pairwise similarity of the samples, using heuristically determined constant thresholds to evaluate the maximum allowed band size deviation; unfortunately, that approach significantly reduces the ability to distinguish between closely related samples. This study presents a new approach based on global multiple alignments of bands of all samples, with an adaptive threshold derived from the detailed migration analysis of a large number of real samples. The proposed approach allows the accurate automated analysis of DNA fingerprint similarities for extensive epidemiological studies of bacterial strains, thereby helping to prevent the spread of dangerous microbial infections.

Complete Genome Sequence of Streptococcus mutans Strain LAB761, Which Harbors Several Bacteriocin Loci, Isolated from a Caries-Active Child in Canada

Streptococcus mutans LAB761 has been isolated from dental plaque collected from a child with severe caries. We report here the complete genome sequence of S. mutans strain LAB761, which has a chromosome of 2.0 Mb.

Streptococcus mutans LAB761 has been isolated from dental plaque collected from a child with severe caries. We report here the complete genome sequence of S. mutans strain LAB761, which has a chromosome of 2.0 Mb. The genome sequence reported herein contains several loci encoding double-glycine-motif peptides and lantibiotic and nonlantibiotic bacteriocins.

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.

Transmission patterns of Streptococcus mutans demonstrated by a combined rep-PCR and MLST approach

OBJECTIVE

Clinical typing methods of the oral pathogen Streptococcus mutans with molecular analysis can be very specific, but expensive. Repetitive extragenic palindromic PCR (rep-PCR) is a relatively inexpensive pre-screening alternative for isolate selection for additional analyses. This study evaluated the prediction accuracy of using rep-PCR to identify S. mutans multilocus sequence typing (MLST) sequence types (ST) among children and their family members. Potential S. mutans strain sources were evaluated for evidence of transmission.

MATERIAL AND METHODS

Ten dendrograms (rep-PCR), with 20 isolates each of the 10 most common S. mutans genotypes, were generated from different subjects. Using a cut-off of 98% similarity, 7-11 isolates of each genotype were selected for MLST analysis to determine ST match/no-match.

RESULTS

Overall, rep-PCR was 75% effective at determining MLST ST match/no-match and 90% effective when applied to related individuals. Most genotypes were further differentiated by MLST. MLST ST diversity was greatest for one genotype (genotype 12, G12) and evidence of transmission among children and their family members was identified by rep-PCR and MLST. Younger children (6 months to 4 years old) shared ST with their mothers but 50% of older children (5-9 years old) had ST not identified in their mother. Six ST were shared between different families and probable source members were identified.

CONCLUSION

This study confirms that rep-PCR offers an affordable option to predict diverse isolates for downstream applications.

CLINICAL RELEVANCE

Using a combined rep-PCR and MLST approach, it is possible to track probable transmission and strain sources for S. mutans genotypes.

Genotypic diversity and phenotypic traits of Streptococcus mutans isolates and their relation to severity of early childhood caries

BACKGROUND

Early childhood caries (ECC) is an aggressive condition that can affect teeth of young children. This study aimed to evaluate genotypic diversity and phenotypic traits of S. mutans isolated from dental biofilms of children with different caries status in comparison with caries free (CF) children.

METHODS

Streptococcus mutans strains were isolated from supragingival biofilm samples of CF, ECC and severe-ECC (S-ECC) children and genotyped by arbitrary-primer polymerase chain reaction - AP-PCR. S. mutans genotypes were tested for their ability to reduce the suspension pH through glycolysis, to tolerate extreme acid challenge and by their ability to form biofilm. Response variables were analyzed by ANOVA/Tukey or Kruskal-Wallis/Mann-Whitney tests at a 5% of significance.

RESULTS

There was an increase in the prevalence of Streptococcus mutans in biofilms with the severity of dental caries. No differences in genotypic diversity and in acidogenicity of genotypes were found among CF, ECC and S-ECC children. S mutans strains with genotypes more characteristic for ECC and S-ECC children formed more biofilms than those identified in CF children. The strains isolated from S-ECC children were highly acid tolerant.

CONCLUSION

Although S. mutans genotypic diversity was similar among the groups of children, phenotypic traits of S. mutans, especially the acid tolerance response, could explain the severity of early childhood caries.