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. 2016 Sep 30;11(9):e0162887.
doi: 10.1371/journal.pone.0162887. eCollection 2016.

Microbiome in the Apical Root Canal System of Teeth with Post-Treatment Apical Periodontitis

José F Siqueira Jr  1 , Henrique S Antunes  1   2 , Isabela N Rôças  1 , Caio T C C Rachid  3 , Flávio R F Alves  1
Affiliations

Microbiome in the Apical Root Canal System of Teeth with Post-Treatment Apical Periodontitis

José F Siqueira Jr et al. PLoS One. .

Abstract

Introduction: Bacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis. This study used a next-generation sequencing approach to identify the bacterial taxa occurring in cryopulverized apical root samples from root canal-treated teeth with post-treatment disease.

Methods: Apical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. DNA was extracted from the powder and the microbiome was characterized on the basis of the V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device.

Results: All samples were positive for the presence of bacterial DNA. Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity. Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. In general, these 4 phyla accounted for approximately 80% of the distinct OTUs found in the apical root samples. Proteobacteria was the most abundant phylum in 6/10 samples. Fourteen genera had representatives identified in all cases. Overall, the genera Fusobacterium and Pseudomonas were the most dominant. Enterococcus was found in 4 cases, always in relatively low abundance.

Conclusions: This study showed a highly complex bacterial community in the apical root canal system of adequately treated teeth with persistent apical periodontitis. This suggests that this disease is characterized by multispecies bacterial communities and has a heterogeneous etiology, because the community composition largely varied from case to case.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Average relative abundance of bacterial phyla composition in root apex samples from teeth with post-treatment apical periodontitis.
Fig 2
Fig 2. Taxonomic assignment (phylum level) of the operational taxonomic units found in root apex samples from teeth with post-treatment apical periodontitis.
Fig 3
Fig 3. Relative abundance of bacterial phyla composition in each one of the 10 root apex samples from teeth with post-treatment apical periodontitis.
Fig 4
Fig 4. Average relative abundance of the top most abundant bacterial genera (left bars), and proportion of occurrence among the root apex samples from teeth with post-treatment apical periodontitis (right bars).
Fig 5
Fig 5. Relative abundance of the top most abundant bacterial genera in each one of the 10 root apex samples from teeth with post-treatment apical periodontitis.
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Grants and funding

This study was supported by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Brazilian Governmental Institutions.

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