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Abstract
β-Haemolytic, Lancefield group C streptococci within the anginosus-species group were shown by genetic and phenotypic criteria to be heterogeneous and to constitute two distinct taxa related at subspecies level to Streptococcus constellatus and Streptococcus anginosus, respectively. The first group, referred to here as DNA group 1, comprised six strains with 86–100% intragroup overall genomic DNA relatedness; five of the strains were originally isolated from the human throat and one was from an abdominal mass. They shared 61–77% DNA relatedness (ΔT m values = 1.2-1.5 °C) with reference strains of S. constellatus and were clearly differentiated from S. constellatus (now named Streptococcus constellatus subsp. constellatus) by the ability to produce β-N-acetylgalactosaminidase, β-acetylglucosaminidase, β-d-fucosidase, β-d-galactosidase and β-d-glucosidase. The name S. constellatus subsp. pharyngis is proposed for these strains on the grounds that they are genetically and phenotypically distinct and exhibit a predeliction for the human throat, being isolated also from cases of pharyngitis. The DNA G+C content is 35–37 mol%. The type strain is MM9889aT (= NCTC 13122T). The second group (DNA group 2) was formed by five β-haemolytic, Lancefield group C strains originally isolated from various human infections. DNA group 2 strains (81–100% intragroup DNA relatedness) shared 60–72% DNA relatedness (ΔT m values = 2.1-4.1 C) with S. anginosus strains NCTC 10713T and MAS 283 but were not dearly differentiated phenotypically from S. anginosus, showed no dear pattern of clinical association, and therefore are not formally proposed as a new subspecies here.
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