Analysis of difference of saliva microbiome between caries-free and caries-active individuals before and after sucrose treatment

Objective To investigate, before and after sucrose challenge, the difference of saliva microbiome between caries-free (CF) and caries-active (CA) individuals, and to explore the potential key microorganisms that is more susceptible to sucrose challenge. Methods Eighteen systemic healthy volunteers, among which 8 were caries-free and 10 were caries-active, were recruited. Saliva samples were collected pre-treatment and at 30 min and 2 h after the sucrose treatment. Microbial diversity and community structure were analyzed and compared using Illumina sequencing platform. Results The diversity and abundance of saliva samples from caries-free individuals was similar to that from caries-active individuals before sucrose treatment. After 2 h of treatment, the microbial diversity of the CA group was significantly higher than that of the CF group (P<0.05). The results of Beta diversity analysis showed no significant difference between the two groups. The dominant species, which were represented as Pseudomonas, Streptococcus, Prevotella, Alloprevotella, Neisseria and Veillonella, in the two groups were similar but different in abundance. There was no significant change in the abundance difference of Veillonella between CF and CA before and after treatment. The abundance differences of Prevotella and Alloprevotella between CF and CA increased and the abundance difference of Neisseria decreased after sucrose treatment. The results of LEfSe analysis showed that Prevotella, as one of the dominant bacteria in the two groups, was significantly more abundant in the CA group than in the CF group after sucrose treatment, suggesting its potential biomarker role. Conclusion The diversity and composition of saliva microbiome changes subject to sucrose challenge, which is more significant in caries-affected individuals. The response of salivary microbe to sucrose challenge is different between caries-free and caries-active individuals. Prevotella is a potential biomarker of caries.