Development of amplified 16S ribosomal DNA restriction analysis for identification of Actinomyces species and comparison with pyrolysis-mass spectrometry and conventional biochemical tests.

Identification of Actinomyces spp. by conventional phenotypic methods is notoriously difficult and unreliable. Recently, the application of chemotaxonomic and molecular methods has clarified the taxonomy of the group and has led to the recognition of several new species. A practical and discriminatory identification method is now needed for routine identification of clinical isolates. Amplified 16S ribosomal DNA restriction analysis (ARDRA) was applied to reference strains (n = 27) and clinical isolates (n = 36) of Actinomyces spp. and other gram-positive rods. Clinical strains were identified initially to the species level by conventional biochemical tests. However, given the low degree of confidence in conventional methods, the findings obtained by ARDRA were also compared with those obtained by pyrolysis-mass spectrometry. The ARDRA profiles generated by the combination of HaeIII and HpaII endonuclease digestion differentiated all reference strains to the species or subspecies level. The profiles correlated well with the findings obtained by pyrolysis-mass spectrometry and by conventional tests and enabled the identification of 31 of 36 clinical isolates to the species level. ARDRA was shown to be a simple, rapid, cost-effective, and highly discriminatory method for routine identification of Actinomyces spp. of clinical origin.