DNA probes in the diagnosis of periodontal microorganisms

The need for a rapid and sensitive microbiological assay has become necessary for both research and clinical diagnostic purposes. This need has become clear as a result of extensive documentation linking specific bacterial species and periodontal destruction. DNA probe technology provides both a sensitive and specific assay and alleviates the concern for transport of fastidious microorganisms. The DNA probe procedure includes (1) disruption of bacterial cells with denaturation of DNA, (2) immobilization of DNA onto a nitrocellulose filter, (3) blocking unbound nitrocellulose with non-specific DNA, (4) hybridization of the filter with 32P-labelled probe, (5) washing and detection of bound probe. At our laboratory, microbiological analysis with whole-genomic and cloned DNA probes has been used on thousands of plaque specimens in several large-scale research projects. In one study, levels (greater than or equal to 10(5)) of Actinobacillus actinomycetemcomitans were significantly higher in subjects under 21 yr than in subjects with adult periodontitis (over 21 yr old). In another study, the distribution of periodontal pathogens throughout the mouth was examined. High levels were selectively found at sites with probing depths of 5 mm or more and bleeding on probing, directing specimen collection to these sites. In contrast, random selection of sites for sampling was found to be a poor method for detecting high levels of pathogens. These data suggest appropriate sites for specimen collection for further research and diagnostic purposes.