Quantitative Analysis of Salivary Oral Bacteria Associated with Severe Early Childhood Caries and Construction of Caries Assessment Model

Abstract

To construct a saliva-based caries risk assessment model, saliva samples from 176 severe early childhood caries (S-ECC) children and 178 healthy (H) children were screened by real-time PCR-based quantification of the selected species, including Streptococcus mutans, Prevotella pallens, Prevotella denticola and Lactobacillus fermentum. Host factors including caries status, dmft indices, age, gender, and geographic origin were assessed in their influence on abundance of the targeted species, which revealed host caries status as the dominant factor, followed by dmft indices (both P < 0.01). Moreover, levels of S. mutans and P. denticola in the S-ECC group were significantly higher than those in the healthy group (P < 0.001 for S. mutans and P < 0.01 for P. denticola). Interestingly, the co-occurrence network of these targeted species in the S-ECC group differed from that from the healthy group. Finally, based on the combined change pattern of S. mutans and P. pallens, we constructed an S-ECC diagnosis model with an accuracy of 72%. This saliva-based caries diagnosis model is of potential value for circumstances where sampling dental plague is difficult.

Figure 1

Verification of the specificity of those two Prevotella primers. (A) Specificity of the primer pair targeting P. denticola. Lane 1–9 showed the amplification result of P. denticola primer pair from the genomic DNA of various oral species. Amplification was positive only when using P. denticola DNA as template. (B) Specificity of the primer pair targeting P. pallens. Lane 1–9 showed the amplification result of P. pallens primer pair from the genomic DNA of various oral species. Amplification was positive only when using P. pallens DNA.

Figure 2

The co-occurrence networks of the targeted species in each of the two hosts groups. The connection lines between two nodes indicate positive correlation between the levels of two species, with color representing the degree of correlation. There was a very strong positive correlation among every species in a pair-wise manner in the healthy group (A). In the S-ECC group, however, the correlation between S. mutans and L. fermentum was weakened, and the correlation between S. mutans and P. pallens was no longer present (B).

Figure 3

ROC curves of the caries classification models. The AUC values of models derived from P. denticola alone (0.47; (A)), L. fermentum alone (0.51; (B)), P. pallens alone (0.57; (C)), or from S. mutans alone (0.61; (D)). (E) The model was built from combining P. pallens and S. mutans. It carries an AUC of 0.72, higher than the single-species models.