is one of the three species currently included in the “anginosus group” of oral or viridans streptococci. In this study 21 strains of were examined in order to determine whether this species, as currently defined, is sufficiently heterogeneous to warrant further subdivision. Phenotypic strain characterization was carried out by performing biochemical tests with a commercial system (Rapid ID32 STREP kit; bioMerieux), by performing tests to determine hyaluronidase production, hemolysis on blood agar, and gliding motility on chocolate agar, by determining Lancefield groups, and by comparing whole-cell polypeptide patterns obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Variations in genotype were determined by studying 16S-23S rRNA intergenic spacer size polymorphisms by PCR amplification, by ribotyping, and by performing DNA-DNA base pairing studies. was found to be heterogeneous at both the species and intraspecies (subspecies) levels. Beta-hemolytic Lancefield group C strains that did not produce hyaluronidase formed a DNA homology group that was separate from the majority of the strains; the members of this group produced a 380-bp intergenic spacer PCR product, exhibited distinct ribotypes, produced an atypical SDS-PAGE pattern, and represented a previously undescribed species in the anginosus group. Two other strains (ATCC 9895 and 1007-77) remained ungrouped as determined by DNA-DNA hybridization and thus represented additional centers of variation at the species level. Hyaluronidase-producing, beta-hemolytic, Lancefield group C strains produced the same atypical SDS-PAGE pattern as beta-hemolytic Lancefield group C strains that did not produce hyaluronidase but differed from the latter organisms by producing a 600-bp intergenic spacer PCR product. In addition, both DNA homology data and ribotyping data suggested that these strains comprise a subspecies of . With the notable exception of the beta-hemolytic Lancefield group C strains that did not produce hyaluronidase, strains ATCC 9895 and 1007-77, and the beta-hemolytic Lancefield group C hyaluronidase-producing strains mentioned above, the strains studied formed a closely related group within which some additional genotypic and phenotypic heterogeneity was observed. The latter group included both strains that fermented mannitol and strains that did not ferment mannitol, as well as strains that exhibited so-called gliding motility. Although no clear-cut division of these organisms was possible, our results indicate that strain NCTC 10713 may not be the most suitable type strain for . We concluded that strains exhibit sufficient heterogeneity to warrant division at both the species and subspecies levels, although insufficient numbers of strains belonging to the putative new taxa have been characterized to allow formal taxonomic proposals to be made.


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