Clinical parameters of individuals with periodontitis and Diabetes Mellitus reveals signatures of the minority microbiota in saliva / Los parámetros clínicos de las personas con periodontitis y diabetes mellitus revelan firmas de la microbiota minoritaria en la saliva / Parâmetros clínicos de indivíduos com periodontite e diabetes mellitus revelam assinaturas da microbiota minoritária na saliva

Aims: This pilot study aimed to describe the majority and minority microbiota of saliva from individuals with advanced periodontitis, with or without type 2 diabetes mellitus (T2D), correlating the relative abundance of microorganisms with clinical parameters. Material/Methods: Six individuals diagnosed with periodontitis were included and classified according to their diagnosis of T2D. Salivary pH, number of teeth with active caries lesions, number of remaining teeth, periodontal and glycemic parameters were evaluated. V4 region amplicons of the 16S rRNA from salivary DNA were sequenced at Ion PGM. Amplicon sequence variants (ASVs) were compared according to the clinical parameters. Results: Correlation showed eight low-abundant bacteria significantly correlated with co-variables, either positively or negatively. The periodontitis-associated bacteria followed the increasing pH and number of remaining teeth. Conclusions: This survey provided potential minority microbiota correlations with clinical parameters, such as number of remaining teeth, FBG, and salivary pH. The ubiquity of some low abundant microorganisms in individuals with advanced periodontitis, exposed or not to type 2 DM, can reveal microbial signatures not yet explored.

Presence of Archaea in dental caries biofilms.

OBJECTIVE: Although the prevalence and functions associated with members of Bacteria are well known in dental caries, the role of Archaea in cariogenic biofilms has not been studied yet. DESIGN: To detect the presence of Archaea in dental caries, a triplicate of carious dentine samples and duplicate of supragingival biofilms were collected, total microbial DNA was extracted and the composition of the microbiota was investigated. Total DNA was submitted to 16S rRNA gene amplification using universal prokaryotic primers; amplicons were sequenced by high-throughput DNA sequencing. As a second strategy to detect Archaea, a representative sample of caries was chosen and other PCR reactions were performed using specific primers targeting the archaeal 16S rRNA gene; amplicons were cloned and sequenced. Annotation of sequences was performed using SILVA database and the relative abundance of genus level OTUs was calculated. RESULTS: The high-throughput sequencing method detected archaeal sequences in all samples (identified as group I.1c of the phylum Thaumarchaeota), although in a very low abundance (≤0.03 % of the total sequences). For the second strategy, 14 archaeal clones were detected, with an OTU affiliated to Methanocella clade, and another one affiliated to group I.1b of the phylum Thaumarchaeota. CONCLUSIONS: Archaeal sequences were detected in dental caries and biofilms from surfaces without caries lesions. DNA sequences of Thaumarchaeota were also identified, showing that overall archaeal diversity in the human oral cavity could be currently underestimated and not restricted to methanogens.