Identification of bacteria enduring endodontic treatment procedures by a combined reverse transcriptase-polymerase...

This study identified the bacterial taxa enduring endodontic treatment procedures by using a combined 16S ribosomal RNA-based reverse-transcriptase polymerase chain reaction (RT-PCR) and reverse-capture checkerboard hybridization approach.

Samples were taken from infected canals of 15 teeth with apical periodontitis before treatment (S1), after chemomechanical preparation with NaOCl as the irrigant (S2), and after interappointment medication with a calcium hydroxide paste (S3). Bacterial presence was first screened by a DNA-based single PCR assay. RNA extracts were subjected to RT-PCR, and the resulting products were surveyed for the presence of 28 targeted taxa by using the checkerboard method.

Bacteria were found in all S1 samples. Detectable levels of bacterial ribosomal RNA, used as an indicator of viability, were observed in 60% of the cases after chemomechanical preparation and 53% after intracanal medication. The most prevalent taxa in S1 were Olsenella uli (67%), Pyramidobacter piscolens (60%), Streptococcus species (53%), and Bacteroidetes clone X083 (53%). Streptococcus species (47%), Fusobacterium nucleatum (40%), and O. uli (33%) prevailed in S2, whereas Streptococcus species (47%), Propionibacterium acnes (27%), and O. uli (27%) were the most frequent taxa in S3.

The present study with a combined molecular approach revealed that bacterial diversity was overall markedly reduced by treatment procedures. Although bacterial taxa more frequently identified in post-treatment samples emerge as potential risk factors for persistent disease, this remains to be determined by longitudinal studies.