Bacteria and Lipoteichoic Acid Detected in Post-Endodontic Treatment Infection

Objectives: Bacteria and their virulence factors, including the lipoteichoic acid (LTA) liberated by the Gram-positives, are the main cause of post-treatment apical periodontitis signs and symptoms. The aim of this work was to study in cases of endodontic failure: a) the root canal microbiota composition; b) the LTA levels; c) the relationship between the microbiota and clinical signs and symptoms.
Methods: Ten patients with apical periodontitis and need for endodontic retreatment were selected. Samples were collected from the root canals. The DNA was extracted and subjected to checkerboard analysis to detect 40 bacterial species. For LTA quantification, Enzyme-Linked Immunosorbent Assay (ELISA) method was used. Pearson's Chi-square test was used to test the null hypothesis that there is no association among the bacterial species and between clinical signs and symptoms and the presence of a particular bacterium/LTA levels (p <0.01).
Results: Bacteria were detected in all samples by checkerboard, including Gram-positives and Gram-negatives, facultatives and strict anaerobes, with an average number of 27 species per canal. The most prevalent species belonged to the phyla Firmicutes, Bacteroidetes and Fusobacteria and to the genera Capnocytophaga, Enterococcus, Eubacterium, Fusobacterium, Gemella, Parvimonas, Prevotella, Staphylococcus and Streptococcus . LTA was found in 100% of the samples, with a mean of 618.69 pg/mL per canal. Highly significant positive (n=7) and negative associations (n=11) (p <0.01) were found between the microbial species.
Conclusions: It was concluded that the root canals microbiota in endodontic failure is heterogeneous, presenting LTA in all cases. Regarding the associations, they were found only between microorganisms and not between microorganisms and clinical signs/symptoms.