Diversity and Sources of Enterococcus Spp in Endodontic Infections

Objectives: Enterococci, especially E.faecalis, have long been associated with persistent endodontic infections. The prevalence of Enterococcus spp in endodontic infections is reported to be about 12-80%. The purpose of this study was to compare diversity and prevalence of enterococci in endodontic infections at various stages of treatment by clonal analysis of 16S rDNA sequences amplified with ubiquitous bacterial primers and by using genus specific primers.

Methods: Tooth surface (that has been disinfected) and root canal (pre-operative, post instrumentation and post-medication) specimens were aseptically obtained from 40 patients with primary (N=26) or persistent (N=14) root canal infection. DNAs were extracted from the specimens according to the protocol described for the QIA Amp DNA mini kit. PCR with ubiquitous 16S rDNA bacterial primers was performed and the products were cloned and sequenced.  Genus specific PCR was done by using primers specific for bacterial tuf gene and identified by direct sequencing followed by phylogenetic analysis.

Results: Fifteen different enterococcal phylotypes were identified from the patient samples with broad range primers. The prevalence of enterococci in pre-operative specimens was 32% by cloning and sequencing and 68% by specific PCR analysis. After endodontic instrumentation, enterococci was more prevalent in primary infections than in persistent infections. The most prevalent phylotypes in the patient samples identified by broad range primers were E.casseliflavus/ flavescens/gallinarum (43%) and E.faecalis (26%); whereas E.casseliflavus (63%) was the most predominant phylotype identified by specific primers.

Conclusions: Enterococcus spp are very prevalent and diverse in endodontic infections and may persist in root canals despite antibacterial protocols used in contemporary endodontic treatment (Supported by grant DE014476 from NIDCR).