Checkerboard DNA-DNA hybridization analysis of endodontic infections

Objective. The purpose of this investigation was to examine the microbiota of infected root canals by using a molecular genetic method. Study design. The presence and levels of 42 bacterial species were determin ed in 28 root canal samples by using whole genomic DNA probes and checkerbo ard DNA-DNA hybridization. To confirm the presence of bacterial DNA in clin ical samples, a polymerase chain reaction with an ubiquitous bacterial prim er was undertaken. Results. The results of the checkerboard DNA-DNA hybridization analysis sho wed that 22 of the 42 DNA probes tested were reactive with 1 or more sample s. 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: Ba cteroides forsythus (39.3% of the cases); Haemophilus aphrophilus (25%); Co rynebacterium matruchotii (21.4%); Porphyromonas gingivalis (17.9%); and Tr eponema 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 ar e difficult or impossible to culture. In addition, our findings support the current concept that endodontic infections are mixed infections of polymic robial etiology.