In-vivo shift of the microbiota in oral biofilm in response to frequent sucrose consumption

Abstract

Caries is associated with shifts of microbiota in dental biofilms and primarily driven by frequent sucrose consumption. Data on environmentally induced in vivo microbiota shifts are scarce therefore we investigated the influence of frequent sucrose consumption on the oral biofilm. Splint systems containing enamel slabs were worn for 3 × 7 days with 7-day intervals to obtain oral biofilm samples. After a three-month dietary change of sucking 10 g of sucrose per day in addition to the regular diet, biofilm was obtained again at the end of the second phase. The microbiota was analysed using Illumina MiSeq amplicon sequencing (v1-v2 region). In addition, roughness of the enamel surface was measured with laser scanning microscopy. The sucrose phase resulted in significant differences in beta-diversity and significantly decreased species richness. It was marked by a significant increase in abundance of streptococci, specifically Streptococcus gordonii, Streptococcus parasanguinis and Streptococcus sanguinis. Enamel surface roughness began to increase, reflecting initial impairment of dental enamel surface. The results showed that frequent sucrose consumption provoked compositional changes in the microbiota, leading to an increase of non-mutans streptococci, hence supporting the extended ecological plaque hypothesis and emphasizing the synergy of multiple bacterial species in the development of caries.

Figure 1

Splint system with bovine enamel slabs used to collect oral biofilm samples (f = frontal; m = mesial; b = buccal).

Figure 2

Study design. Samples of dental biofilm grown on enamel slabs embedded in splint systems were collected 3 times (a–c) in two phases (I, II). During phase I (grey), the 11 study participants kept their regular diet while in phase II (pink), frequent sucrose consumption was introduced for 3 months.

Figure 3

Relative average abundances (%) of the different phyla and the most abundant genera (>2% abundance among all samples) of the 11 study participants in phases I and II.

Figure 4

Relative average abundance (%) of the different Streptococcus species of the 11 study participants in phases I and II. Streptococcus spp. refers to those OTUs which could not be unambiguously assigned to one of the oral Streptococcus species.

Figure 5

Species richness and beta-diversity in oral biofilm from 11 study participants in phases I and II. (A) Box plot depicting the decrease in species richness of all 33 samples in phase II. (B) NMDS plot depicting the beta-diversity in phases I and II. Samples from the second phase with radically altered microbial composition are displayed individually. Those outliers were mainly dominated by members of the phylum Proteobacteria.

Figure 6

Box plots of the abundance of different taxa in oral biofilm that increase in phase II. The bottom and top of the box indicate the first and third quartiles, the line inside the box the median and the ends of the whiskers the 10th and 90th percentile values. Outliers are plotted as circles. Significant increases were detected in relative abundances of the phylum Firmicutes, the genus Streptococcus and the species S. gordonii, S. sanguinis and S. parasanguinis respectively.

Figure 7

Box plots of the abundance of different taxa in oral biofilm that decrease in phase II. The bottom and top of the box indicate the first and third quartiles, the line inside the box the median and the ends of the whiskers the 10th and 90th percentile values. Outliers are plotted as circles. Significant decreases were found in relative abundances of the phylum Proteobacteria, the family Pasteurellaceae, the class Bacteroidia, and the genus Porphyromonas.

Figure 8

Arithmetic average of the roughness profile (Ra) [µm] of the enamel specimens for each week in phases I and II.