Sample Abstracts

Oral Research Sample

Real-Time Quantitative PCR and Culture Analyses of Enterococcus Faecalis in Primary and Refractory Endodontic Infections
J.M. Williams*, M. Trope, M. Heffernan, D.C. Shugars, University of North Carolina, Chapel Hill, NC

Enterococcus faecalis is frequently implicated in endodontic treatment failures. Limited genotype-based quantitative data exist on E. faecalis in primary (PI) and refractory infections (RI). This study sought to develop a real-time quantitative PCR (qPCR) assay to measure E.f. and total bacteria loads in RI and PI, compare qPCR and culture in bacterial quantification and detection, and evaluate endodontic treatment effectiveness on E.f. clearance. Duplicate intracanal samples were collected preinstrumentation (S1), postinstrumentation/irrigation (S2) and post-Ca(OH)₂ treatment (S3) from 15 PI and 14 RI, totaling 29 single-rooted teeth. Samples were cultured on selective and nonselective media in aerobic and anaerobic conditions or analyzed by qPCR using ubiquitous and E.f.-specific primers and fluorogenic probes. qPCR detection range was 101–108 copies/DNA. qPCR was more sensitive than culture in detecting E. faecalis and total bacteria at all time points (McNemar, p<0.05).>E.f. detection was greater using qPCR than culture (time-qPCR/culture: S1-42.8%/14.2%, S2-57%/7.1%, S3-50%/0%; Wilcoxon, p<0.05).>E.f. was detected by qPCR/culture in S1-13%/6.7%, S2-20%/0% and S3-20%/0%. E. faecalis comprised 4% (qPCR)-14% (culture) RI median total bacterial levels at S1 versus 0.03%(qPCR)-3.8% (culture) of PI. Treatment reduced median S1-S3 E.f. counts 10-fold by qPCR and culture in RI; in PI, reduction was detected by culture but not qPCR. E. faecalis detection by qPCR was up to 6-fold more sensitive than culture. E. faecalis was found more frequently and comprised a larger proportion of total bacteria in RI than PI. Following endodontic therapy, E. faecalis and total bacteria were detected in both infection types. Supported b