Molecular Identification of Cultivable Bacteria From Infected Root Canals Associated With Acute Apical Abscess

The objective of this study was to investigate the bacterial composition present in root canals of teeth associated with acute apical abscess by molecular identification (16S rRNA) of cultivable bacteria. Two hundred and twenty strains isolated by culture from 20 root canals were subjected to DNA extraction and amplification of the 16S rRNA gene (PCR), followed by sequencing. The resulting nucleotide sequences were compared to the GenBank database from the National Center of Biotechnology Information through BLAST. Strains not identified by sequencing were submitted to clonal analysis. The association of microbiological findings with clinical features and the association between microbial species were also investigated. Fifty-nine different cultivable bacteria were identified by 16S rRNA gene sequencing, belonging to 6 phyla, with an average number of 6 species per root canal. Molecular approaches allowed identification of 99% of isolates. The most frequently identified bacteria were Prevotella spp., Pseudoramibacter alactolyticus, Parvimonas micra, Dialister invisus, Filifactor alocis, and Peptostreptococcus stomatis. Positive association was found between Prevotella buccae and Pseudoramibacter alactolyticus and between Parvimonas micra and Prevotella nigrescens (both p<0.05). It was concluded that the microbiota of infected root canals associated with acute apical abscess is diverse and heterogeneous, composed mainly of anaerobic Gram-negative bacteria, with the great majority belonging to the phyla Firmicutes and Bacteroidetes.