AUTHOR=Havsed Kristian , Stensson Malin , Jansson Henrik , Carda-Diéguez Miguel , Pedersen Anders , Neilands Jessica , Svensäter Gunnel , Mira Alex 

TITLE=Bacterial Composition and Metabolomics of Dental Plaque From Adolescents

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.716493

DOI=10.3389/fcimb.2021.716493

ISSN=2235-2988

ABSTRACT=<p>Supragingival dental plaque samples were collected from 40 Swedish adolescents, including 20 with caries lesions (CAR) and 20 caries-free (CF). Fresh plaque samples were subjected to an <italic>ex vivo</italic> acid tolerance (AT) test where the proportion of bacteria resistant to an acid shock was evaluated through confocal microscopy and live/dead staining, and the metabolites produced were quantified by <sup>1</sup>H Nuclear Magnetic Resonance (<sup>1</sup>H NMR). In addition, DNA was extracted and the 16S rRNA gene was sequenced by Illumina sequencing, in order to characterize bacterial composition in the same samples. There were no significant differences in AT scores between CAR and CF individuals. However, 7 out of the 10 individuals with highest AT scores belonged to the CAR group. Regarding bacterial composition, <italic>Abiotrophia</italic>, <italic>Prevotella</italic> and <italic>Veillonella</italic> were found at significantly higher levels in CAR individuals (p=0.0085, 0.026 and 0.04 respectively) and <italic>Rothia</italic> and <italic>Corynebacterium</italic> at significantly higher levels in CF individuals (p=0.026 and 0.003). The caries pathogen <italic>Streptococcus mutans</italic> was found at low frequencies and was absent in 60% of CAR individuals. Random-forest predictive models indicate that at least 4 bacterial species or 9 genera are needed to distinguish CAR from CF adolescents. The metabolomic profile obtained by NMR showed a significant clustering of organic acids with specific bacteria in CAR and/or high AT individuals, being <italic>Scardovia wiggsiae</italic> the species with strongest associations. A significant clustering of ethanol and isopropanol with health-associated bacteria such as <italic>Rothia</italic> or <italic>Corynebacterium</italic> was also found. Accordingly, several relationships involving these compounds like the Ethanol : Lactate or Succinate : Lactate ratios were significantly associated to acid tolerance and could be of predictive value for caries risk. We therefore propose that future caries risk studies would benefit from considering not only the use of multiple organisms as potential microbial biomarkers, but also their functional adaptation and metabolic output.</p>