ABSTRACT: Microbial diversity in primary and therapy-resistant endodontic infections

Microbial diversity in primary and therapy-resistant endodontic infections

A. FOUAD, University of Maryland, Baltimore, USA, B.J. PASTER, The Forsyth Institute, Boston, MA, USA, R. NANDAKUMAR, University of Maryland Dental School, Baltimore, USA, and S. BARBUTO, Forsyth Institute, Boston, MA, USA

Objectives: The purpose of this study was to perform an extensive analysis of microbial diversity in primary and persistent root canal infections, before and after treatment procedures, using a 16S rDNA clonal analysis.

Methods: Forty-seven endodontic specimens were included: 33 from cases with necrotic pulps and 14 from cases requiring retreatment for persistent disease. Eleven and 5 patients reported having significant symptoms in primary and persistent cases, respectively. Specimens were obtained prior to treatment, after chemomechanical preparation as well as after medication with Ca(OH)2 and final irrigation. PCR with broad range 16S rDNA bacterial primers was performed, and the products were cloned into the vector pCR 2.1-TOPO TA and transformed into E. coli One-Shot TOP10. Plasmid DNA from clones was purified and sequenced. Phylogenetic analysis was performed to reach final identity. Sequences with less than 98% similarity with published sequences were excluded.

Results: Analysis was completed on 3116 clones, with the following mean number of clones per specimen / mean number of phylotypes per specimen:

	Pre-operative	Post-instrumentation	Post-medication
Primary	43/9	28/10	40/10
Persistent	49/12	44/8	46/9
Symptomatic	44/10	19/10	45/10
Asymptomatic	49/10	30/8	41/9

A total of 318 different phylotypes were identified. Over 100 clones each were identified from: Lactococcus lactis, Micrococcus sp. EF114312, Enterococcus casseliflavus, Bacteroidetes sp. X083 and Actinomyces israelii. Only 55 phylotypes had more than 10 clones in the database, and 125 phylotypes were identified from only one clone. Thirty one percent of cases did not have detectable bacteria in one or both post-operative specimens. However, in cases where bacteria persisted, the identified phylotypes were different from pre-operative profiles in all groups.

Conclusions: Endodontic infections contain a large diversity of bacteria, and treatment procedures result in a change in the phylotypes identified (Supported by grant DE015320-01-A1 from NIDCR)

Seq #150 - Infection Control
9:00 AM-10:30 AM, Friday, July 4, 2008
Metro Toronto Convention Centre Room 714A

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