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In this work, genomic DNA of Streptococcus pyogenes, S. mutans and S. sobrinus was isolated using two methods: either using the detergent cetyltrimethylammonium bromide (CTAB) at 65ºC; or by applying ultrasound to a mixture of silica and celite in CTAB. The composite method that used ultrasound was the more efficient, allowing the straightforward extraction of genomic DNA from Gram-positive bacteria with good quality and reproducibility.

A cárie dentária é uma doença infecciosa, multifatorial com prevalência na infância, sendo a bactéria Streptococcus mutans principal agente etiológico, existindo uma correlação entre concentração desta na cavidade bucal e incidência da doença. Neste contexto, o trabalho objetivou relacionar incidência clínica da cárie, com concentração da bactéria na saliva de escolares, visando avaliar o risco à doença e implantar ações para seu controle. Foram realizadas avaliações de determinantes sócio-econômicos, dieta, condições clínicas e análise microbiológica da saliva. A partir da concentração de unidades formadoras de colônias (UFC/mL de saliva) em Agar Mitis Salivarius acrescido de sacarose e bacitracina;as crianças foram classificadas como alto, médio ou baixo risco de desenvolvimento à doença. Análise clínica baseada nos índices CPO-D, ceo-d e atividade de cárie foi realizada e os dados confrontados com a análise microbiológica. Um total de 237 crianças, na faixa etária de 5 a 12 anos foi avaliado. A partir dos dados clínicos, observou-se que 73% das crianças apresentaram alta prevalência de cárie, das quais 83,5% apresentaram alta concentração de S. mutans na saliva, verificando correlação bisserial por ponto, significativa entre a detecção do risco e a manifestação clínica da doença. Os resultados forneceram subsídios para ações de intervenção no processo saúde/doença.

The detection of Streptococcus mutans isolates with high genetic variability in different individuals indicates the occurrence of transmissibility. In this context, nine low-income families (40 individuals in total) with similar social conditions were assessed to identify the bioserotypes of S. mutans using both biochemical and RAPD markers and to establish the degree of similarity among the intra-familial isolates. The polymorphism analysis used the coefficient of Jaccard in both a Principal Coordinates Analysis (PCO) and in a UPGMA clustering method. A total of 157 isolates were obtained from salivary samples, using the morphology of colonies recovered using MSB agar as indicators. From those, 64 were characterized biochemically as S. mutans and 10 as S. sombrinus. Genetic variability among isolates based on RAPD markers was not consistent with their intra-familial distribution. In particular, some individuals might have experienced multiple infections given the high genetic variability among their isolates. The occurrence of 4 isolates with 100% genetic similarity is indicative of intra-familial transmission.

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Aim: To characterize the genetic variability of Streptococcus mutans isolates and to correlate this variability with different colonization profiles observed during dental caries in a sample of children. Methods: S. mutans samples were isolated from the saliva of 30 children with varying histories of dental caries, and they were characterized according to morphological and biochemical markers and the sequences of their 16S-23S intergenic spacer region. The genetic variability of the isolates was first assessed using Random Amplified Polymorphic DNA (RAPD) markers. Next, the isolates were differentiated by sequencing a specific region of the gene encoding the enzyme glucosyltransferase B (gtfB). Results: Characterization using RAPD markers uncovered significant genetic variability among the samples and indicated the existence of clusters, which allowed us to reconstruct both the origin and clinical history of the disease. By sequencing the 16S-23S intergenic region, it was found that all of the isolates belonged to the species S. mutans. Based on the genetic similarity of the isolates and pattern of amino acid variations identified by partial sequencing of the gtfB gene, base-pair changes were identified and correlated with different virulence patterns among the isolates. Conclusions: The partial sequencing of the gtfB gene can be a useful tool for elucidating the colonization patterns of S. mutans. As amino acid variations are likely to be correlated with differences in biological risk, molecular characterization, such as that described in this paper, could be the key for assessing the development of dental caries in children.

OBJECTIVE: Caries is a multifactorial infectious disease and the main etiological agent is the bacteria Streptococcus mutans due to its virulence factors, which enable the adherence to dental enamel and favours the formation of dental biofilm through the production of extracellular polysaccharides. The transmission of S. mutans can occur between people, often within families. The present study aimed to evaluate the intrafamily genetic pattern of S. mutans through partial sequencing of the gene that encodes the glucosyltransferase β (gtfB) enzyme.METHODS: We previously analyzed saliva samples from 40 individuals from nine families, and it was obtained 64 isolates biochemically characterized as S. mutans. The isolates were evaluated by random amplification of polymorphic DNA (RAPD). Those with greater similarity were characterized by partial sequence 16S rRNA gene and the gtfB gene sequencing.RESULTS: It was observed genetic similarity among strains isolated from individuals with caries activity; while isolates from individual without caries showed that they are genetically distinct, suggesting a different virulence pattern.CONCLUSION: The present results demonstrated that partial sequencing of the gtfB gene showed to be a potential marker to investigate genetic pattern and virulence of S. mutans, deserving further investigation in order to identify families at risk of caries.