The current classification of is problematic. Many bovine strains, including the type strain, are not typical of strains derived from humans, especially in physiologic characteristics. Further, a number of strains physiologically resembling some (MG) strains carry the group D antigen and have been classified as (var.) strains. In this work, we compared the physiologic characteristics and deoxyribonucleic acid relatedness of human strains of and (var.), the bovine type strain, and selected bile-tolerant, esculin-hydrolyzing strains of viridans streptococci. Our results indicate a lack of relationship between strains derived from humans and the bovine type strain. Although, like the classic strains of human origin, the bovine type strain was able to hydrolyze starch, it differed from human strains in that it failed to form acid from mannitol and melibiose. The (var.) strains did not hydrolyze starch or form acid from mannitol. They were distinguished from the bile-tolerant, esculin-hydrolyzing (MG) strains by their inability to decarboxylate arginine, their ability to form acid from melibiose, and their production of the Lancefield group D antigen. All strains of human origin, including the (var.) strains, formed a single deoxyribonucleic acid homology group distinct from the bovine type strain. Further, none of the strains were homologous to the (MG) or strains studied. Our findings suggest that (var.) forms a subspecies of strains of human origin and that strains derived from humans should be removed from the taxon.


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