Metagenomic analysis of oral microbiome in young children aged 6-8 years living in a rural isolated Chinese province.

BACKGROUND

The mixed dentition is an important transition period from primary teeth to permanent teeth. However, the caries prevalence of first permanent molar in mixed dentitions was about 30%, which almost represent the caries rate of permanent teeth in this period of time. Therefore, we assessed the oral bacterial profiles in young children (age 6-8) with mixed dentition with or without first molar caries for providing the research basis of caries etiology.

METHODS

We collected samples of supragingival plaque and saliva from the children living in Guizhou, a rural isolated province in China. Then, we performed DNA extraction and purification followed by 454 pyrosequencing of the V1-V3 hypervariable regions of the 16S rRNA and compared our results with those of previous research.

RESULTS

(i) We analyzed 48,320 unique sequences that represented 18 phyla, 29 classes, 44 orders, 74 families, 129 genera, 15,003 species-level OUT in plaque and saliva samples; (ii) longitudinally, there was the "healthy core microbiome" between healthy deciduous dentition and early mixed dentition, for example, Neisseria, Porphyromonas, Selenomonas etc.; (iii) horizontally, there also existed the "healthy core microbiome" in early mixed dentition, for example, Neisseria, Streptococcus, Prevotella etc.; (iv) the dominant bacteria detected by Lefse in caries group including Actinomycetaceae, Streptobacillus (p < 0.05) and those in caries-free group including Gammaproteobacteria, Pasteurellaceae, Aggregatibacter, Chloroflexi, (p < 0.05).

CONCLUSIONS

The oral cavity is a highly heterogeneous ecosystem with the "healthy core microbiome" in children, although microbial composition shifts along with aging. In addition, the abundance and diversity of microbiota vary between caries and caries-free groups verify the ecological plaque hypothesis.