title: Checkerboard DNA-DNA hybridization analysis of endodontic infections.
abstract: OBJECTIVE
  The purpose of this investigation was to examine the microbiota of infected root canals by using a molecular genetic method.
  
  
  METHODS
  The presence and levels of 42 bacterial species were determined in 28 root canal samples by using whole genomic DNA probes and checkerboard DNA-DNA hybridization. To confirm the presence of bacterial DNA in clinical samples, a polymerase chain reaction with an ubiquitous bacterial primer was undertaken.
  
  
  RESULTS
  The results of the checkerboard DNA-DNA hybridization analysis showed that 22 of the 42 DNA probes tested were reactive with 1 or more samples. The number of bacterial species in the root canal samples ranged from 1 to 17 (mean, 4.7). Seventeen of the 28 root canal samples were positive for at least 1 DNA probe. The most prevalent species found were as follows: Bacteroides forsythus (39. 3% of the cases); Haemophilus aphrophilus (25%); Corynebacterium matruchotii (21.4%); Porphyromonas gingivalis (17.9%); and Treponema denticola (17.9%).
  
  
  CONCLUSIONS
  The microbiologic data of the present investigation indicated that molecular genetic methods can provide significant additional knowledge regarding the endodontic microbiota by detecting bacterial species that are difficult or impossible to culture. In addition, our findings support the current concept that endodontic infections are mixed infections of polymicrobial etiology.
authors.affiliation: Department of Endodontics, School of Dentistry, Estácio de Sá University, Rio de Janeiro, Brazil.
authors.forename: J F
authors.initials: JF
authors.lastname: Siqueira
authors.forename: I N
authors.initials: IN
authors.lastname: Rôças
authors.forename: R
authors.initials: R
authors.lastname: Souto
authors.forename: M
authors.initials: M
authors.lastname: de Uzeda
authors.forename: A P
authors.initials: AP
authors.lastname: Colombo
mesh_terms: D000293:Adolescent; D000328:Adult; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification; D001424:Bacterial Infections / Q000175:diagnosis* / Q000382:microbiology; D015342:DNA Probes; D004269:DNA, Bacterial / Q000235:genetics* / Q000302:isolation & purification; D003786:Dental Pulp Cavity / Q000382:microbiology; D003788:Dental Pulp Diseases / Q000175:diagnosis* / Q000382:microbiology; D006801:Humans; D008875:Middle Aged; D009693:Nucleic Acid Hybridization / Q000379:methods
chemical_list: D015342:DNA Probes; D004269:DNA, Bacterial