Genetic Profiling of the Microbiota Associated With Root Caries

Objectives: Many studies have used cultivation methods to study the microbiota of root caries lesions. However, the number of uncultivable bacteria is high and they can only be investigated by using culture-independent methods. We tested the hypothesis that the composition of the microbial community associated with active root caries, inactive root caries and sound exposed root surfaces are different. Methods: Four different sample types were examined: plaque from the sound root surface in patients with (I) and without (II) root caries, dentine from leathery (inactive) lesions (III) and soft (active) lesions (IV). Denaturing gradient gel electrophoresis (DGGE) was used to analyse the 16S rRNA-genes of Actinomyces spp., Streptococcus spp., Prevotella spp., Firmicutes and Fusobacterium spp. with universal and taxon-specific primers. The DGGE band patterns were compared and the species diversity analysed. Results: Significant differences in the number of bands were found in the DGGEs obtained with universal primers (I: 14.5 ± 1.0SE, II: 14.0 ± 1.0SE, III: 16.3 ± 1.4SE, IV: 19.2 ± 1.4SE), taxon-specific primers for Actinomyces spp. (I: 3.0 ± 0.5SE, II: 5.3 ± 0.7SE, III: 6.6 ± 1.0SE, IV: 3.7 ±0.8SE) and Lactobacillus spp. which were only detected in soft lesions. The Actinomyces DGGE fingerprinting profiles showed sample-specific band patterns although the diversity within each sample type was up to 50%. Species identification also revealed many novel phylotypes in each taxon and a high diversity between patients with the same sample type but no specific microbiota was associated with sample type. Conclusion: This study indicated that there is no specific microbiota associated with root caries although in soft lesions Lactobacillus spp. increased while many other taxa were present. The demineralisation process associated with root caries may increase the diversity but each individual harboured his own microbiota. Funded by King's College London.