In the late autumn of 1968 and 1970, an epizootic occurred among yellowtails, Seriola quinqueradiata, in culture farms in Kochi Prefecture. Affected fishhad large abscesses with hemorrhagic borders in th body surface.
An etiological agent was isolated from spleen and kidney of moribund yellowtails. The isolated organism was gram-negative, nonsporning rods with polar flagella, and usually 0.5 to1.0 by 1.5 to 4.4μ in size. On nutrient agar colonies developed within 24hours at 25deg;C. The optimal temperature for the growth was about 25deg;Cto 30deg;C. Nogrowth occurred at 5deg;C or 37deg;C. Oxidase and catalase were positive. Glucose, levulose, mannose, galactose and glycerol were attacked by oxidation, whereas trehalose, erythritol, adonitol, mannitol, sorbitol and inositol were not attacked. Indole, hydrogen sulfide, nitrate, methylred test, gelatin liquefaction, VP and LV reaction were negative. The organism produced diffusible fluorescin, particularly in iron-deficient media. It was sensitive to chloramphenicol, oxytetracycline, tetracycline, kanamycin, erythromycin, colistin, nalidixic acid and polymixin B. The organism was therefore identified asPseudomonas putida.