Identification of clinical isolates of Actinomyces species by amplified 16S ribosomal DNA restriction analysis

Amplified 16S ribosomal DNA (rDNA) restriction analysis (ARDRA), using enzy mes HaeIII and HpaII, was applied to 176 fresh and 299 stored clinical isol ates of putative Actinomyces spp. referred to the Anaerobe Reference Unit o f the Public Health Laboratory Service for confirmation of identity. Result s were compared,vith ARDRA results obtained previously for reference strain s and with conventional phenotypic reactions. Identities of some strains we re confirmed by analysis of partial 16S rDNA sequences. Of the 475 isolates , 331 (70%) were clearly assigned to recognized Actinomyces species, includ ing 94 isolates assigned to six recently described species. A further 52 is olates in 12 ARDRA profiles were designated as apparently resembling recogn ized species, and 44 isolates, in IS novel profiles, were confirmed as memb ers of genera other than Actinomyces. The identities of 48 isolates in nine profiles remain uncertain, and they may represent novel species of Actinom yces. For the majority of species, phenotypic results, published reactions for the species, and ARDRA profiles concurred. However, of 113 stored isola tes originally identified as A. meyeri or resembling A. meyeri by phenotypi c tests, only 21 were confirmed as A. meyeri by ARDRA; 63 were reassigned a s A. turicensis, 7 as other recognized species, and 22 as unidentified acti nomycetes. Analyses of incidence and clinical associations of Actinomyces s pp. add to the currently sparse knowledge of some recently described specie s.