養殖ハマチのノカルデイア症に関する研究-I

Abstract

Since the late summer of 1967, nocardiosis has been prevalent among yellowtails, Seriola quinqueradiata, in fish farms in the western part of Japan and has caused serious damage. In 1968, the causative organism was first isolated by KARIYA et al. who named it Nocardia kampachi. In the present paper, morphological and biochemical characteristics of five organisms isolated from lesions of diseased yellowtails obtained from farms in Kochi Prefecture were studied. The organisms were non-motile gram-positive rods which occasionally showed branching, and were feebly acid-fast. They were non-sporing, and produced aerial hyphae. Catalase, hydrogensulfide production, starch hydrolysis, and nitrate reduction were positive. Decomposition of hypoxanthine and tyrosine was feebly positive. Tests for oxidase, urease, indole production, gelatin liquefaction, and decomposition of casein and xanthine were negative. They utilized citrate and pyruvate, but did not benzoate, mucoate, oxalate and propionate on the medium containing diammonium hydrogen phosphate as the nitrogen source. They showed growth at neither 10°C nor 37°C and survived at 50°C for 4 hours in the nutrient broth. The organisms had much in common with those of Nocardia kampachi, but could be distinguishable from those of Nocardia asteroides (EPPINGER).