Genotypic Diversity and Virulence Traits of Streptococcus mutans

The aim of this study was to compare the genotypic diversity and virulence traits of Streptococcus mutans isolated from carious dentin before and after partial dentin caries removal (PDR) and sealing. Carious dentin samples were obtained three months before and after the PDR and cavity sealing. Up to seven isolates of each morphological type of S. mutans were selected and strain identity was confirmed using gtfB primer. Genotyping was performed by arbitrary primer-PCR (AP-PCR). Acidogenesis and acidurance of the genotypes were evaluated as virulence traits. A paired t-test and a Wilcoxon test were used to compare the virulence of genotypes. A total of 48 representative S. mutans isolates were genotyped (31 before and 17 after the sealing). At least one of the genotypes found before the sealing was also found on dentin after the sealing. The number of genotypes found before the sealing ranged from 2 to 3 and after the sealing from 1 to 2 genotypes. No difference was observed in the acidogenesis and acidurance between genotypes isolated before and after the sealing. In conclusion, genotypic diversity of S. mutans decreased after the PDR and sealing, but the virulence traits of S. mutans remained unchangeable

The role of Candida albicans in root caries biofilms: an RNA-seq analysis

Objective: This study sought to analyze the gene expression of Candida albicans in sound root surface and root caries lesions, exploring its role in root caries pathogenesis. Methodology: The differential gene expression of C. albicans and the specific genes related to cariogenic traits were studied in association with samples of biofilm collected from exposed sound root surface (SRS, n=10) and from biofilm and carious dentin of active root carious lesions (RC, n=9). The total microbial RNA was extracted, and the cDNA libraries were prepared and sequenced on the Illumina Hi-Seq2500. Unique reads were mapped to 163 oral microbial reference genomes including two chromosomes of C. albicans SC5314 (14,217 genes). The putative presence of C. albicans was estimated (sum of reads/total number of genes≥1) in each sample. Count data were normalized (using the DESeq method package) to analyze differential gene expression (using the DESeq2R package) applying the Benjamini-Hochberg correction (FDR<0.05). Results: Two genes (CaO19.610, FDR=0.009; CaO19.2506, FDR=0.018) were up-regulated on SRS, and their functions are related to biofilm formation. Seven genes ( UTP20 , FDR=0.018; ITR1 , FDR=0.036; DHN6 , FDR=0.046; CaO19.7197 , FDR=0.046; CaO19.7838 , FDR=0.046; STT4 , FDR=0.046; GUT1 , FDR=0.046) were up-regulated on RC and their functions are related to metabolic activity, sugar transport, stress tolerance, invasion and pH regulation. The use of alternative carbon sources, including lactate, and the ability to form hypha may be a unique trait of C. albicans influencing biofilm virulence. Conclusions: C. albicans is metabolically active in SRS and RC biofilm, with different roles in health and disease

Microbial load after selective and complete caries removal in permanent molars : a randomized clinical trial

O objetivo deste ensaio clínico randomizado foi comparar os microrganismos remanescentes após tratamentos baseados em remoção total de tecido cariado e selamento e a remoção seletiva de tecido cariado e selamento. Pacientes com lesões de cárie ativas em molares permanentes foram divididos aleatoriamente em dois grupos: grupo teste (remoção seletiva de tecido cariado-SCR; n=18), e grupo de controle (remoção total de tecido cariado-CCR; n=18). Amostras de dentina foram obtidas após a remoção da tecido cariado e após 3 meses de selamento das cavidades. Streptococcus spp., Streptococcus mutans, Lactobacillus spp. e microrganismos viáveis totais foram cultivados para contagem de células e frequência de isolamento de espécies. CCR resultou em menores contagens totais de microorganismos viáveis (p≤0,001), Streptococcus spp. (p≤0,001) e Lactobacillus spp. (p≤0,001) inicialmente. Entretanto, após o selamento, uma redução significativa nas contagens totais de microrganismos viáveis, Streptococcus spp. e Lactobacillus spp. resultou em nenhuma diferença entre os grupos após 3 meses. Conclui-se que a remoção seletiva de cárie é tão seletiva quanto a remoção completa de cárie na redução da infecção dentinária após três meses com selamento da lesão.The aim of this randomized clinical trial was to compare the remaining microbial load after treatments based on complete and selective caries removal and sealing. Patients with active carious lesions in a permanent molar were randomly allocated into 2 groups: a test group (selective caries removal-SCR; n=18) and a control group (complete caries removal - CCR; n=18). Dentin samples were collected following the excavation and three months after sealing. Streptococcus species, Streptococcus mutans, Lactobacillus species, and total viable microorganisms were cultured to count the viable cells and frequency of species isolation. CCR resulted in significant lower total viable microorganisms counts (p≤0.001), Streptococcus species (p≤0.001) and Lactobacillus species (p≤0.001) initially. However, after sealing, a decrease in total viable microorganisms, Streptococcus species, and Lactobacillus species in the SCR resulted in no difference between the groups after 3 months. In conclusion, selective caries removal is as effective as complete caries removal in reducing dentin bacterial load 3 months after sealing