A cross-sectional metagenomic analysis of the microbial ecology in symptomatic apical periodontitis - An <i>in vivo</i> study

<h4>Background</h4>Symptomatic apical periodontitis (SAP) is a painful inflammatory disease driven by root canal infection. A detailed understanding of its microbial ecology, compared to a noninfectious baseline, is needed.<h4>Aims</h4>This study aimed to characterize the microbial ecology of SAP using 16S ribosomal (RNA) 16S rRNA metagenomic sequencing and compare it to control teeth undergoing root canal treatment after trauma.<h4>Materials and methods</h4>This cross-sectional study included 10 patients with SAP and 10 control patients. Pulpal samples were collected aseptically. Microbial DNA was extracted, and the full-length 16S rRNA gene was sequenced through Oxford Nanopore Technology. Analysis was performed using QIIME2.<h4>Statistical analysis used</h4>Microbial abundances and diversity indices were compared using an independent samples t-test or Mann-Whitney U-test (P < 0.05 significant).<h4>Results</h4>The SAP microbiome was dysbiotic and enriched in anaerobes. Veillonella parvula was highly abundant in SAP (mean 13.1%) but absent in controls. Species like Dialister pneumosintes and Prevotella melaninogenica were found almost exclusively in SAP. Commensals including Faecalibacterium prausnitzii were significantly reduced.<h4>Conclusion</h4>SAP is associated with a distinct microbial signature defined by the enrichment of anaerobic pathobionts and a loss of commensals, revealing a polymicrobial, dysbiotic community.