Streptococcus didelphis sp nov., a streptococcus with marked catalase activity isolated from opossums (Didelphis virginiana) with suppurative dermatitis and liver fibrosis

beta-Haemolytic, catalase-positive, Gram-positive cocci that formed chains in broth media but did not react with Lancefield group antisera were isolated from skin lesions, spleen, liver and lungs of nine opossums, including eight from a research colony and one from a wildlife rehabilitation organization. The isolates had vigorous catalase activity that was retained on initial passage on non-blood-containing media. but this activity was lost in subsequent passages. The use of standard phenotypic tests did not lead to satisfactory identification of these organisms beyond the genus level, even if the aberrant catalase reaction was not considered. The 16S rRNA gene sequence of the isolates was most similar (96%) to Streptococcus dysgalactiae, but distinct from that species as 16S rRNA gene similarity of different strains of S. dysgalactiae was >99 %, Characterization of biochemical reactions and cell-wall fatty acid profiles also revealed significant differences between the opossum isolates and all other known Streptococcus spp,. thus it is proposed as a new species with the name Streptococcus didelphis, sp, nov. The type strain is ATCC 700828(T).