The Oral Microbiome In The Elderly With Root And Coronal Caries

Background: Dental caries has been a significant oral health issue in humans with a polymicrobial etiology.With the aging of the population,the elderly have increasingly suffered from dental caries in recent years.The oral microbiota are closely related to the initiation and progression of dental caries.A comprehensive study of the oral microbiome is required to understand its polymicrobial etiology.The results of previous studies are limited and remain controversial.Objective: To gain thorough knowledge of the microbiological etiology of elderly individuals with caries,and to investigate the change of bacteria and fungi in different sites and status.It is expected to provide novel methods for its prevention and treatment.Methods: Subjects meet the inclusion criteria were recruited after a comprehensive oral examination.Samples were collected from dental plaque and carious lesion.The bacterial 16 S rDNA and fungal ITS DNA were respectively amplified using PCR and sequenced by Illumina MiSeq high-throughput sequencing.Results:1?The analysis of bacterial community structure: A total of 32 phyla,67 classes,133 orders,232 families,431 genera and 738 species were detected from all the samples.The predominant phyla were Proteobacteria,Bacteroidetes,Firmicutes,Fusobacteria,Actinobacteria and Saccharibacteria.The bacterial compositions were largely consistent in different groups,but different relative abundances could be observed,with higher abundances of Streptococcus,Actinomyces,and Propionibacterium in caries groups.The Venn diagram showed 306 unique bacteria in root carious lesion,while the core microbiome was defined with 247 bacteria shared among other groups.Alpha diversity showed no significant difference in bacterial richness but decreased diversity in root caries.Beta diversity analysis was performed by PCA,showing gradually diffuse trend in coronal caries and a quite different distribution in root carious lesion.The biomarkers of different groups were defined by LEfSe analysis to identify potential caries-related and health-related bacteria.The network analysis revealed positive interactions among predominant genera.The functional prediction was performed by PICRUSt,indicating vigorous microbial metabolism in the oral bacterial community.2?The analysis of fungal community structure: Fungi were detected only in a small part of samples,and most of them were collected from root caries patients.Candida albicans was the absolute predominant fungus,occupying 98% of all the fungi detected.Beta diversity analysis showed clear distinction between coronal and root caries.The Venn diagram demonstrated many unique fungal species in root carious lesion.The network analysis showed even more complex relationships among fungi.Conclusion: The oral microbiome in the elderly with caries in different sites or status showed different microbial community structures and diversity.Healthy controls showed higher bacterial diversity and more stable community structure,while root caries showed significant changes in microbiol community.Different carious sites or status showed similar compositions but different relative abundances among groups.The abundances of some bacteria may be closely related to the process of caries in the elderly.Fungi,especially Candida albicans,were also potentially corresponded to caries process.Oral microbiota exhibited complex interactions and vigorous metabolism.