The species was proposed to accommodate a heterogeneous group of streptococci associated with infections in animals and human beings. This taxon is now considered to include animal isolates of α-haemolytic group C streptococci, previously called ; animal and human isolates of β-haemolytic group C streptococci, previously called ; β-haemolytic group L strains associated with infections in animals and, rarely, in humans; and β-haemolytic group L strains isolated from humans. DNA-DNA reassociation experiments (hydroxyapatite method) and multilocus enzyme electrophoresis (MEE) were performed on reference strains and clinical isolates to determine the genetic relationships among these different phenotypic categories. DNA-DNA hybridization tests showed that they were related at the species level, despite the phenotypic and host heterogeneity. Both genotypic and phenotypic characterizaton indicated that could be separated into two major sub-groups. The first sub-group contained α-haemolytic strains that showed levels of DNA relatedness with the type strain of ranging from 84 to 90% and from 82 to 88% under optimal (55 °C) and stringent (70 °C) conditions respective. The second sub-group contained β-haemolytic strains showing levels of relatedness ranging from 71 to 79% (55 °C) and from 62 to 73% (70 °C). Percentage divergence varied from 0·5 to 1·0% (α-haemolytic group) and from 2·0 to 3·5% (β-haemolytic group). A dendrogram based on phenotypic similarity between the enzyme bands produced by MEE showed a Jaccard similarity coefficient of 0·45 between the subclusters formed by the two sub-groups. The results of phenotypic and genotypic characterization were consistent with a published proposal to divide into two subspecies, subsp. and subsp. , with a few .


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