Abstract
Dynamic alterations in oral microbiota are closely related to the development of dental caries;however, changes in salivary microbiota during this process have not been extensively studied. In addition, increasing evidence suggests that oral microbiome profiles differ according to dentition stages, but it is unclear whether they change with age during the same dentition, such as deciduous dentition. These two aspects were investigated in a 2-year follow-up study, and caries-free preschool children with complete deciduous dentition were enrolled. Saliva was collected and oral examination was conducted at the beginning of this trial, and then every subsequent 6 months for a total of five time points (T0, T1, T2, T3, and T4). Based on the clinical examination of teeth at the end of the trial, subjects were divided into health-to-health (H-H, N = 11) and health-to-caries (H-C, N = 12) groups at every time point. A total of 115 saliva samples from 23 subjects was detected by sequencing 16S rDNA V3-V4 hypervariable regions with the Illumina MiSeq platform to obtain microbiome profiles, and 100 samples finally passed quality control for further analyses. A total of 4,328,852 high-quality sequencing reads passed quality-control testing, representing 14 phyla, 27 classes, 43 orders, 67 families, and 127 genera. An α diversity analysis showed that salivary microbial diversity was similar in all groups, and a β diversity analysis showed that salivary microbial community structure changed with dental caries. Linear discriminant analysis effect size (LEfSe) analysis revealed that the abundance of the genera Atopobium, Megasphaera, and Veillonella increased significantly, while that of the genera Shuttleworthia and Rothia decreased significantly with the development of dental caries. Megasphaera and Veillonella were enriched at the early stage of deciduous dentition whereas Peptococcus, Rothia, and Treponema were enriched at the later stage. The core microbiome in the H-H and H-C groups comprised 26 and 29 genera, respectively, with statistical differences observed in 11 shared core genera. These results provide new insights into variations in the salivary microbiome related to dental caries and age in the deciduous dentition period.
Highlights
Microbes reside in different parts of the human body, and the number of them to human cells is found to be much closer to 1:1, rather than at least 10:1 as commonly reported (Sender et al, 2016)
We studied variations in the salivary microbiota related to caries by comparing H-H and H-C groups, while looking at changes in the salivary microbiota with age during the deciduous dentition period by comparing H-H groups between T0 and T4 time points
Different hypervariable regions (V1-V9) of bacterial 16S rRNA gene can be analyzed for accuracy and reliability; it was previously found that the V3-V4 and V4-V5 regions yielded the most accurate results, regardless of sequencing technology and quality (Claesson et al, 2010)
Summary
Microbes reside in different parts of the human body, and the number of them to human cells is found to be much closer to 1:1, rather than at least 10:1 as commonly reported (Sender et al, 2016). The oral cavity is one of the most important habitats for microorganisms and considerable efforts have been made to characterize human oral microbiotas (He and Shi, 2009). The mouth is a constantly changing habitat for microbes, in part due to the emergence and later replacement of deciduous teeth, as well as diet, environment, and host genetics, among other factors (Human Microbiome Project, 2012). Studies have shown that oral microbial community composition changes throughout life, from neonates to primary dentition, mixed dentition, and permanent dentition of young adults, adults, and the elderly (Crielaard et al, 2011; Lif Holgerson et al, 2015; Xu et al, 2015; Shi et al, 2016). Agerelated changes in the oral microbiome for a given dentition status, such as deciduous dentition, have not been adequately addressed
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