Genotypic diversity of Streptococcus mutans in children with and without early childhood caries- A systematic review

Does high sugar intake really alter the oral microbiota?: A systematic review

OBJECTIVES

Diet is one of the main factors influencing the diversity and interactions of the oral microbiota. The purpose of this study is to determine the impact of sugar intake on the microbial diversity and bacteria that predominate under these conditions.

MATERIAL AND METHODS

A systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guide, using the PubMed, Scopus, and Science Direct databases and combinations of the words "microbiota," "microbiology," "bacteria," "sugars," "dysbiosis," "caries," "microbiome," "oral microbial," and "oral microbiota profile pattern." The selection criteria included year, language, type of publication, comparison of microbiota during low and high sugar intake, and bacterial identification by molecular sequencing of the 16S subunit of ribosomal RNA.

RESULTS

Out of a total of 374 papers that came up after the initial search, 8 met the criteria for this review. The papers included research on populations comprising children, young adults, and adults, with most of the studies reporting selection criteria for the participants and using validated instruments to determine sugar intake. Apart from one study, all others reported for high sugar intake conditions a significant decrease in microbial diversity of the oral microbiome and the predominance of several bacterial genera or species, including Streptococcus, Scardovia, Veillonella, Rothia, Actinomyces, and Lactobacillus.

CONCLUSIONS

Sugar-rich diets have a significantly unfavorable effect on the diversity and balance of oral microbiota; however, further studies are required to determine the exact role of sugar in microbial interactions.

Ozone Therapy for Early Childhood Caries (ECC) Treatment: An In Vivo Prospective Study

The present study aimed to evaluate the effectiveness of ozone therapy in (1) increasing the compactness of decayed dentin (main aim), (2) reducing dentin hypersensitivity, (3) decreasing the salivary bacterial count, and (4) improving the quality of life in ECC-affected children during a 3-month follow-up. A total of 20 subjects uncooperative with conventional restorative treatment were treated with a 60 s ozone application/week (OzoneDTA®) for 4 weeks. Patients were evaluated at T0 = baseline; T1 = after ozone cycle and T2, T3, T4 = 1, 2, 3-month follow-up, respectively. Dentin compactness was evaluated according to the Affected Dentine Scale (ADS) proposed by the authors; dentin hypersensitivity was recorded with the Wong–Baker Faces Pain Rating Scale (WBFPRS); salivary bacteria were measured with the Saliva Check Mutans Test and quality of life with the Early Childhood Oral Health Impact Scale (ECOHIS). ADS values and salivary bacteria count results were analyzed using non-parametric tests. Statistically significant differences were detected for both parameters between T0 and T1 (p < 0.01). At T1, dentin hypersensitivity was resolved and quality of life improved. Ozone therapy is a simple and painless approach, which might be useful for controlling caries’ progression in uncooperative children until appropriate cooperation is achieved.

Genotypic and phenotypic characterization of Streptococcus mutans strains isolated from patients with dental caries

Background and Objectives

The oral cavity harbors numerous Streptococcus mutans strains which display remarkable genotypic and phenotypic diversity. This study evaluated the genotypic and phenotypic diversity of 209 S. mutans strains isolated from 336 patients with dental caries and compared with the universal reference strain, UA159.

Materials and Methods

Selective cultivation on mitis-salivaries-bacitracin agar and species-specific polymerase chain reaction (PCR) was carried out to isolate and identify the 209 S. mutans isolates from 336 patients with dental caries. Arbitrarily primed polymerase chain reaction (AP-PCR), PCR amplification of specific gene, acid production and biofilm formation capacity were performed to evaluate the genotypic and phenotypic variation. Student's t-test and Chi-square test were used for analysis of variables and a probability (P) of <0.05 was considered as significant.

Results

Our study revealed a high degree of genotypic and phenotypic variability among the clinical strains. We observed significant differences in colony morphology, generation time, biofilm formation, and acid production while growing in culture medium. All the clinical isolates were able to lower pH while growing in Todd-Hewitt broth. Consistent with phenotypic variations, we also observed genotypic variation by AP-PCR and gene specific PCR. AP-PCR analysis suggested that most of the patients with dental caries have distinct type of S. mutans strains. Genes related to various two component systems were highly conserved among the isolated strains, however, bacteriocin encoding genes such as nlmAB, nlmC were absent in nearly half of the clinical isolates.

Conclusion

Our results support that S. mutans clinical isolates have wide genotypic diversity and show variation in growth kinetics, acid production, acid tolerance and biofilm formation capacity and indicates the presence of diverse mechanism to initiate and establish the biofilm lifestyle which leads to tooth decay.