Viridans group streptococci allows streptococcal strains to be assigned to species within the viridans group streptococci.

The non-pyogenic streptococci are subdivided into the Mitis, Anginosus, Salivarius, Mutans, and Bovis groups, of which the first three are often referred to as viridans streptococci.

The Mitis group currently includes the important pathogen S. pneumoniae and twelve other validly described species, S. australis,  S. cristatus (formerly S. crista), S. gordonii, S. infantis, S. mitis, S. oligofermentans, S. oralis, S. parasanguinis (formerly S. parasanguis), S. peroris, S. pseudopneumoniae, S. sanguinis (formerly S. sanguis) and S. sinensis

The Anginosus group includes three recognized species, S. anginosus, S. constellatus (including two subspecies subsp. constellatus and subsp. pharyngis) and S. intermedius.

The Salivarius group includes S. salivarius, S. vestibularis, and S. thermophilus. All viridans streptococci (with the exception of S. thermophilus, which is not associated with humans) are commensals of the human upper respiratory tract and, excepting S. pneumoniae, they are pathogenic only when they gain access to the blood stream.

Viridans group streptococci have been strikingly resistant to satisfactory classification (partly, perhaps, due to recombination among closely related species), reflected in frequently changing nomenclature and significant problems of identification by phenotypic analysis and by sequencing of 16S rRNA genes.

In contrast, trees based on the concatenated sequences of seven house-keeping genes can identify sequence clusters that can be assigned as species clusters by the location on the tree of the type strains of each of the viridans group species.  The viridans group pages of this website allow strains to be assigned to viridans species by sequencing the seven gene fragments from the query strain and submitting them to this site.  The sequences of the seven loci of your query strain are concatenated and are joined to those of all strains within the viridans group database, and a tree is constructed. The resulting tree shows whether your strain falls within one of the known viridans species clusters or within an unassigned sequence cluster (a potential new species) or is a unique divergent genotype.

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The form contains sequences from S.parasanguinis strain SK264 so you can explore the site.

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