title: Comparison of Bacterial Community Composition of Primary and Persistent Endodontic Infections Using Pyrosequencing.
abstract: BACKGROUND
  Elucidating the microbial ecology of endodontic infections (EIs) is a necessary step in developing effective intracanal antimicrobials. The aim of the present study was to investigate the bacterial composition of symptomatic and asymptomatic primary and persistent infections in a Greek population using high-throughput sequencing methods.
  
  
  METHODS
  16S amplicon pyrosequencing of 48 root canal bacterial samples was conducted, and sequencing data were analyzed using an oral microbiome-specific and a generic (Greengenes) database. Bacterial abundance and diversity were examined by EI type (primary or persistent), and statistical analysis was performed by using non-parametric and parametric tests accounting for clustered data.
  
  
  RESULTS
  Bacteroidetes was the most abundant phylum in both infection groups. Significant, albeit weak associations of bacterial diversity were found, as measured by UniFrac distances with infection type (analyses of similarity, R = 0.087, P = .005) and symptoms (analyses of similarity, R = 0.055, P = .047). Persistent infections were significantly enriched for Proteobacteria and Tenericutes compared with primary ones; at the genus level, significant differences were noted for 14 taxa, including increased enrichment of persistent infections for Lactobacillus, Streptococcus, and Sphingomonas. More but less abundant phyla were identified using the Greengenes database; among those, Cyanobacteria (0.018%) and Acidobacteria (0.007%) were significantly enriched among persistent infections. Persistent infections showed higher phylogenetic diversity (PD) (asymptomatic: PD = 9.2, standard error [SE] = 1.3; symptomatic: PD = 8.2, SE = 0.7) compared with primary infections (asymptomatic: PD = 5.9, SE = 0.8; symptomatic: PD = 7.4, SE = 1.0).
  
  
  CONCLUSIONS
  The present study revealed a high bacterial diversity of EI and suggests that persistent infections may have more diverse bacterial communities than primary infections.
authors.affiliation: Department of Endodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece. Electronic address: gtzanet@dent.uoa.gr.
authors.forename: Giorgos N
authors.initials: GN
authors.lastname: Tzanetakis
authors.affiliation: Department of Cell Biology and Physiology and Microbiome Core Facility, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina.
authors.forename: M Andrea
authors.initials: MA
authors.lastname: Azcarate-Peril
authors.affiliation: Laboratory of Health Physics, Radiobiology and Cytogenetics, NCSR "Demokritos", Athens, Greece.
authors.forename: Sophia
authors.initials: S
authors.lastname: Zachaki
authors.affiliation: Department of Endodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Panos
authors.initials: P
authors.lastname: Panopoulos
authors.affiliation: Department of Endodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Evangelos G
authors.initials: EG
authors.lastname: Kontakiotis
authors.affiliation: Department of Periodontology, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Phoebus N
authors.initials: PN
authors.lastname: Madianos
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina.
authors.forename: Kimon
authors.initials: K
authors.lastname: Divaris
mesh_terms: D000208:Acute Disease; D000328:Adult; D002908:Chronic Disease; D003786:Dental Pulp Cavity / Q000382:microbiology*; D005260:Female; D006115:Greece; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods; D006801:Humans; D008297:Male; D064307:Microbiota / Q000235:genetics; D011671:Pulpitis / Q000382:microbiology*
keywords: Bacterial diversity; oral microbiome; persistent infection; primary endodontic infection; pyrosequencing