Characterization of Actinomyces isolates from infected root canals of teeth: Description of Actinomyces radicidentis sp nov.

Two strains of a previously undescribed Actinomyces-like bacterium were rec overed in pure culture from infected root canals of teeth. Analysis by bioc hemical testing and polyacrylamide gel electrophoresis of whole-cell protei ns indicated that the strains closely resembled each other phenotypically b ut were distinct from previously described Actinomyces and Arcanobacterium species. Comparative 16S rRNA gene-sequencing studies showed the bacterium to be a hitherto unknown subline within a group of Actinomyces species whic h includes Actinomyces bovis, the type species of the genus. Based on phylo genetic and phenotypic evidence, we propose that the unknown bacterium isol ated from human clinical specimens be classified as Actinomyces radicidenti s sp. nov. The type strain of Actinomyces radicidentis is CCUG 36733.