脊椎変形ブリの脳から分離された非溶血性連鎖球菌

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Two species of streptococci were isolated from the brain of the vertebral deformed yellowtail cultured in Lake Hamana, Shizuoka Prefecture. One species was α-hemolytic and the other was non-hemolytic. The α-hemolytic isolates were identified as the well-known etiological agent of streptococcicosis in yellowtail.<BR>The non-hemolytic Streptococcus did not grow in media containing 0.1 % methylene blue milk, 6.5 % NaCl, 10% and 40% bile. Growth at pH 9.6 was positive, but growth at 10°C and 45°C, and heat tolerance (60°C for 30 min) were negative. Final pH in glucose broth was 4.5. The isolate did not hydrolyze gelatin, starch, esculin and arginine, but hydrolyzed sodium hippurate. This non-hemolytic Streptococcus was not classified as any of Lancefield's serological groups. This Streptococcus was placed in the Streptococcus group I, B because growth at 10°C and 45°C were negative and hydrolysis of sodium hippurate was positive. The bacterium, however, was not identical in biochemical characteristics with any formerly established species of the genus Streptococcus.<BR>The non-hemolytic Streptococcus showed fatal pathogenicity for yellowtail by intraperitoneal injection. Further work is required to explain between the isolate and the vertebral deformity.
日本魚病学会の論文