Identification of oral Actinomyces species using DNA probes

Abstract

Oral Actinomyces comprise a major segment of both the supra- and subgingival microbiota; however, little is known about the distribution of individual species in different sites or clinical conditions. The purpose of the present investigation was to develop DNA probes for suggested species and genotypes of oral Actinomyces. Whole genomic DNA probes to 12 human oral species and/or serotypes were labeled with digoxigenin and used to seek cross-reactions among the taxa using the checkerboard DNA-DNA hybridization assay. The Actinomyces formed three distinct groups: 1) Actinomyces georgiae, Actinomyces meyeri and Actinomyces odontolyticus serotypes I and II; 2) Actinomyces viscosus and Actinomyces naeslundii serotypes I, II, III and WVA 963; and 3) Actinomyces gerencseriae and Actinomyces israelii. Cross-reactions among taxa were detected and minimized by increasing the temperature of the post-hybridization high-stringency wash to 80 degrees C. Despite the elevation in high stringency wash temperature, cross-reactions among strains of the A. naeslundii/A. viscosus group persisted. Probes for two of the three currently recognized genospecies in this group were prepared by removing the DNA in common between cross-reacting species using subtraction hybridization and polymerase chain reaction. Nine species and genospecies could be clearly separated by a combination of whole genomic and subtraction hybridization probes and by increasing the high-stringency wash temperature. A total of 195 fresh isolates of Actinomyces were grouped in a blind study using DNA probes and separately by SDS-PAGE protein profiles. Concordance between the two methods was 97.3%. The probes and hybridization conditions were tested for their ability to detect the Actinomyces species and genospecies in samples of supragingival and subgingival plaque from periodontitis subjects using checkerboard DNA-DNA hybridization. The probes detected the species in samples of supragingival and subgingival plaque. We concluded that whole genomic and subtraction hybridization DNA probes facilitate the detection and enumeration of species and genospecies of Actinomyces in plaque samples.

Life as an endodontic pathogen

“…Identification of Actinomyces species has been hampered by problems with traditional biochemical methods of characterization. Although some studies have applied DNA hybridization methods (120, 189–191), these are not readily applicable and reproducible from one lab to another. The partial characterization of the 16S rRNA gene (192) has facilitated the development of probes suited to widespread application (193–195).…”

Actinomyces and Related Organisms in Human Infections

“…A. odontolyticus has been shown to be one of the predominant Actinomyces species in developing biofilms on tooth surfaces in subjects of all ages, and the proportions found were not related to periodontal disease status (31). In a study characterizing 195 fresh Actinomyces isolates collected from supra-and subgingival plaque samples of five adults with chronic periodontitis, A. oris (formerly A. viscosus serotype II) was the isolate most commonly identified, followed by A. gerencseriae, A. naeslundii, A. georgiae, and A. israelii; A. meyeri was not found (32). In general, members of the genus Actinomyces are not considered to play a pathogenic role in periodontitis.…”

Application of MLST and Pilus Gene Sequence Comparisons to Investigate the Population Structures of Actinomyces naeslundii and Actinomyces oris

“…Previous studies have also reported on the intra- and inter-species diversities of A. naeslundii and A. oris , as A. naeslundii genospecies 1 and 2 using DNA fingerprinting [11], ribotyping [5], [12], amplified 16S ribosomal DNA restriction analysis (ARDRA) [4], [13], DNA probes [14], sequence analysis of fimA genes [9] and REP-PCR amplicons analysis [10]. All these studies have demonstrated extensive heterogeneity within each taxon.…”