Diverse bacterial profile in extraradicular biofilms and periradicular lesions associated with persistent apical periodontitis.

AIM To characterize the bacterial community present in the extraradicular biofilm and periradicular lesions associated with persistent apical periodontitis. METHODOLOGY Eighteen adult patients who presented with persistent periradicular lesions after root canal treatment and scheduled for endodontic surgery were selected. During surgery, extraradicular samples of biofilms and periradicular lesions were collected. Ten pairs of periradicular lesions and extraradicular biofilm samples were randomly selected for ribosomal 16S rRNA cloning and sequencing. A Wilcoxon's rank-sum test was used to compare total bacterial counts and the levels of individual genera and species between the two groups (P < 0.05). RESULTS Overall, seventy-three phylotypes belonging to 6 different phyla were identified from 1000 sequenced clones. M. timidum, S. intermedius and E. faecalis predominated in both extraradicular biofilm and periapical lesions. P. propionicus, A. adiacens, P. prevotii, C. gracilis and P. aeruginosa were found in significantly higher levels in the extraradicular biofilm than periapical lesions, while P. micra and A. rimae were more abundant in periapical lesions (P < 0.05). CONCLUSIONS The microbial profile of extraradicular biofilms differed from periapical lesions, indicating the presence of diverse bacterial populations in these regions. Several genera and species were significantly associated with the formation of extraradicular biofilm.