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Updated: Jan 24, 2026

Exploring the Root Microbiome: Extracting Bacterial Community Data from the Soil, Rhizosphere, and Root Endosphere
Published on: May 2, 2018
Metatranscriptomic Insights into Bacterial Activity, Virulence, and Antimicrobial Resistance in the Root Canal
Larissa O Dantas1, George T M Candeiro2, Ana C B Pereira1
1Department of Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil.
Introduction:
This study employed metatranscriptomics to investigate the endodontic microbiome and resistome in acute apical abscesses (AAA) and asymptomatic apical periodontitis (AAP).
Methods:
Root canal samples were collected from 20 patients, including 10 cases of AAA and 10 cases of AAP. RNA sequencing was conducted using the NovaSeq 6000 system. Taxonomic analysis utilized the expanded Human Oral Microbiome Database (eHOMD) database and functional annotation was executed using the DIAMOND and EGGNOG databases. Resistome analysis was conducted with the Comprehensive Antibiotic Resistance Database (CARD) and BacMet - Antibacterial Biocide and Metal Resistance Database. Differential expression analysis was carried out using DESeq2 from the DESeq2 R package (P < .05).
Results:
Taxonomic analysis showed more gram-negative species in AAA samples (P < .05), particularly from the Bacteroidota phylum. In functional analysis, Tannerella forsythia and Streptococcus anginosus group (SAG) showed the highest transcriptional activity in AAA. T. forsythia displayed high expression of Rag/SusD proteins, suggesting a potential virulence mechanism. The main protein family found in both conditions was the adenosine triphosphate-binding cassette (ABC) transporter. Transcripts possibly involved in resistance against various antibiotics (cephalosporins, fluoroquinolones, lincosamides, macrolides, tetracyclines), metals (silver, chromium, zinc), and disinfectants (phenolic compounds, acids, and bases) were identified.
Conclusions:
T. forsythia and SAG demonstrated high activity within the root canal microbiome in cases of AAA, suggesting their involvement in the pathogenicity of the community associated with acute infections. The ABC transporter may play a significant role in antimicrobial resistance through an antibiotic efflux mechanism and contribute to tolerance against disinfectants and antiseptics.
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