A study of small-colony, beta-haemolytic, Lancefield group C streptococci within the anginosus group: description of Streptococcus constellatus subsppharyngis subsp nov., associated with the human throat and pharyngitis

beta-Haemolytic, Lancefield group C streptococci within the anginosus-speci es group were shown by genetic and phenotypic criteria to be heterogeneous and to constitute two distinct taxa related at subspecies level to Streptoc occus constellatus and Streptococcus anginosus, respectively. The first gro up, referred to here as DNA group 1, comprised six strains with 86-100% int ragroup overall genomic DNA relatedness; five of the strains were originall y isolated from the human throat and one was from an abdominal mass. They s hared 61-77% DNA relatedness (Delta T-m values = 1.2-1.5 degrees C) with re ference strains of S. constellatus and were clearly differentiated from S. constellatus (now named Streptococcus constellatus subsp. constellatus) by the ability to produce beta-N-acetylgalactosaminidase, beta-N-acetylglucosa minidase, beta-D-fucosidase, beta-D-galactosidase and beta-D-glucosidase. T he name S. constellatus subsp. pharyngis is proposed for these strains on t he grounds that they are genetically and phenotypically distinct and exhibi t a predeliction for the human throat, being isolated also from cases of ph aryngitis. The DNA G+C content is 35-37 mol%. The type strain is MM9889a(T) (= NCTC 13122(T)). The second group (DNA group 2) was formed by five beta-h aemolytic, Lancefield group C strains originally isolated from various huma n infections. DNA group 2 strains (81-100% intragroup DNA relatedness) shar ed 60-72% DNA relatedness (Delta T-m values = 2.1-4.1 degrees C) with S. an ginosus strains NCTC 10713(T) and MAS 283 but were not clearly differentiat ed phenotypically from S. anginosus, showed no clear pattern of clinical as sociation, and therefore are not formally proposed as a new subspecies here .