title: Susceptibility of as-yet-uncultivated and difficult-to-culture bacteria to chemomechanical procedures.
abstract: BACKGROUND
  A significant portion of the bacteria taking part of the microbiome associated with apical periodontitis still remain to be cultivated and phenotypically characterized. This molecular study evaluated the prevalence of selected as-yet-uncultivated and difficult-to-culture bacterial taxa in infected root canals and their susceptibility to chemomechanical procedures.
  
  
  METHODS
  Root canals of single-rooted teeth with apical periodontitis were prepared using rotary nickel-titanium instruments and 2.5% sodium hypochlorite as the irrigant. DNA extracts from samples taken before (S1) and after (S2) chemomechanical preparation were surveyed for the presence of 7 as-yet-uncultivated phylotypes and 1 difficult-to-culture species using end-point polymerase chain reaction. Samples were also subjected to quantitative analysis of total bacteria and levels of the 2 most prevalent taxa.
  
  
  RESULTS
  Bacteroidaceae sp. HOT-272 (24%) and Fretibacterium fastidiosum (20%) were the most prevalent taxa in S1. Their mean counts in S1 were 8.25 × 10(3) and 2.13 × 10(3) rRNA gene copies, corresponding to 0.18% and 0.55% of the total bacteria. Chemomechanical debridement promoted a highly statistically significant reduction in total bacterial counts (P < .001), but 64% of the canals were still positive for bacterial presence. Of the target taxa, only Bacteroidaceae sp. HOT-272 and F. fastidiosum were detected in S2 (each one in 1 sample). The reduction in counts of both taxa was also highly significant (P < .001).
  
  
  CONCLUSIONS
  Findings confirmed that several as-yet-uncultivated and difficult-to-grow bacterial taxa can participate in the microbiome associated with apical periodontitis. Two of them were found in relatively high prevalence but rarely as a dominant species. Chemomechanical procedures were highly effective in completely eliminating these taxa or at least substantially reducing their numbers.
authors: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Isabela N
authors: IN
authors: Rôças
authors: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Mônica A S
authors: MA
authors: Neves
authors: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors: José C
authors: JC
authors: Provenzano
authors: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil. Electronic address: jf_siqueira@yahoo.com.
authors: José F
authors: JF
authors: Siqueira
mesh_terms: D001419:Bacteria / Q000145:classification*; D058491:Bacterial Load; D001431:Bacteriological Techniques; D001438:Bacteroidaceae / Q000145:classification / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000032:analysis; D003722:Dental Alloys / Q000737:chemistry; D003786:Dental Pulp Cavity / Q000382:microbiology; D003790:Dental Pulp Necrosis / Q000382:microbiology; D004867:Equipment Design; D006089:Gram-Negative Anaerobic Bacteria / Q000145:classification / Q000302:isolation & purification; D006801:Humans; D045851:Megasphaera / Q000145:classification / Q000302:isolation & purification; D064307:Microbiota; D009532:Nickel / Q000737:chemistry; D010485:Periapical Periodontitis / Q000382:microbiology*; D010641:Phenotype; D016133:Polymerase Chain Reaction / Q000379:methods; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000379:methods*; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D014025:Titanium / Q000737:chemistry
chemical_list: D004269:DNA, Bacterial; D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite
keywords: Apical periodontitis; bacterial reduction; endodontic treatment; molecular microbiology; uncultivated bacteria