title: Microbial Ecosystem Analysis in Root Canal Infections Refractory to Endodontic Treatment.
abstract: BACKGROUND
  The purpose of this study was to combine multiple displacement amplification and checkerboard DNA-DNA hybridization to qualitatively and quantitatively evaluate the microbiota present in infections refractory to endodontic treatment.
  
  
  METHODS
  The subjects of this study were 40 patients presenting with periapical lesions refractory to endodontic treatment. Samples were taken by scraping or filing root canal walls with a #10 K-type hand file. Sample DNA was amplified by multiple displacement amplification, and the levels of 107 bacterial taxa were analyzed by checkerboard DNA-DNA hybridization. The taxa were divided into 3 distinct microbial populations depending on their mean proportion in samples (% DNA probe counts ± standard error of the mean) as follows: dominant (≥3.0%), subdominant (>1.6%-3.0%), and residual (≤1.6%) populations. The significance of differences was determined using the Mann-Whitney test.
  
  
  RESULTS
  The taxa present with the highest mean proportions (constituting the dominant population) were Corynebacterium diphtheriae (8.03 ± 0.98), Porphyromonas gingivalis (5.42 ± 2.09), Streptococcus sobrinus (5.33 ± 0.69), and Stenotrophomonas maltophilia (4.72 ± 1.73). Among the subdominant population were Eubacterium saphenum (3.85 ± 1.06), Helicobacter pylori (3.16 ± 0.62), Dialister pneumosintes (3.12 ± 1.1), Clostridium difficile (2.74 ± 0.41), Enterobacter agglomerans (2.64 ± 0.54), Salmonella enterica (2.51 ± 0.52), Mobiluncus mulieris (2.44 ± 0.6), and Klebsiella oxytoca (2.32 ± 0.66). In the population of bacteria present at the lowest mean proportions (the residual population), Bacteroides ureolyticus (0.04 ± 0.01), Haemophilus influenzae (0.04 ± 0.02), and Prevotella oris (0.01 ± 0.01) were found at the lowest mean proportions. Enterococcus faecalis was detected in the residual population (0.52 ± 0.26).
  
  
  CONCLUSIONS
  The microbial climax community in teeth refractory to endodontic treatment not only harbors medically important species but also contains distinct microbial consortia present with different population levels.
authors.affiliation: Departamento de Odontologia Restauradora, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Luiz Carlos Feitosa
authors.initials: LC
authors.lastname: Henriques
authors.affiliation: Faculdade de Odontologia, Universidade de Itaúna, Itaúna, Minas Gerais, Brazil.
authors.forename: Luciana Carla Neves
authors.initials: LC
authors.lastname: de Brito
authors.affiliation: Departamento de Odontologia Restauradora, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Warley Luciano Faria
authors.initials: WL
authors.lastname: Tavares
authors.affiliation: Periodontology, University of North Carolina at Chapel Hill School of Dentistry, Chapel Hill, North Carolina; Departamento de Bioquímica e Imunologia Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Ricardo Palmier
authors.initials: RP
authors.lastname: Teles
authors.affiliation: Departamento de Bioquímica e Imunologia Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Leda Quércia
authors.initials: LQ
authors.lastname: Vieira
authors.affiliation: Periodontology, University of North Carolina at Chapel Hill School of Dentistry, Chapel Hill, North Carolina; Departamento de Bioquímica e Imunologia Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Flávia Rodrigues
authors.initials: FR
authors.lastname: Teles
authors.affiliation: Departamento de Odontologia Restauradora, Faculdade de Odontologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. Electronic address: sobrinho.bhz@gmail.com.
authors.forename: Antônio Paulino Ribeiro
authors.initials: AP
authors.lastname: Sobrinho
mesh_terms: D001419:Bacteria / Q000302:isolation & purification*; D015342:DNA Probes; D004269:DNA, Bacterial / Q000032:analysis; D003786:Dental Pulp Cavity / Q000382:microbiology*; D003790:Dental Pulp Necrosis / Q000382:microbiology; D006801:Humans; D064307:Microbiota; D009693:Nucleic Acid Hybridization; D010483:Periapical Diseases / Q000382:microbiology*; D012390:Root Canal Therapy
chemical_list: D015342:DNA Probes; D004269:DNA, Bacterial
keywords: Checkerboard DNA–DNA hybridization; endodontic treatment failure; multiple displacement amplification; root canal–treated teeth