Comparative oral metagenome insight into acute and chronic root canal infections

Abstract

Background: In the dynamic progression of root canal infections, the resultant change in environmental conditions directs the adaptation of the microbiome in terms of richness, evenness, and diversity. Objective: The goal of this study is to contrast the interradicular bacterial community structures of teeth in acute and chronic stages and investigate potential microorganisms associated with persistent apical periapical infections. Methods: Interradicular samples were collected from 10 teeth in the apical periodontitis group and 10 teeth in the chronic apical periodontitis group. High-throughput next-generation sequencing (NGS)–based microbial identification through the Illumina platform was used to characterize the complex intraradicular microbial communities in acute and chronic root canal infections. Results: Bacteria were the major domain, with a prevalence of >97% (acute cases: 98.11% and chronic cases: 97.6%) compared to eukaryotes and archaea. Bacterial diversity was relatively higher in acute compared to chronic conditions under 10 and 9 phyla, 79 and 64 genera, and 172 and 135 species, respectively. These endodontically infecting bacteria belonged to Firmicutes (47.21%), Bacteroidetes (20.07%), and Proteobacteria (10.72%) in acute conditions, while in the chronic stage, Firmicutes (40.85%), Proteobacteria (27.80%), and Actinobacteria (14.79%) were abundant. The phylum Candidatus Saccharibacteria was exclusively found in acute samples. Spirochaetes and Synergistetes were found predominantly in acute infections compared to chronic infections. Bacillus and Lactobacillus were found in equal and highest abundance under the phylum Firmicutes in both conditions. Conclusion: This study provides information on the differential microbial community present in the apical root canal system of teeth with acute and chronic apical periodontitis and contributes to new approaches or channels for future research on preventive measures and therapeutic protocols during disease progression and treatment. However, functional characterization and detection of antimicrobial resistance in these two clinical conditions can supplement these findings for deciding routine drug treatment for periodontal infections.