Characteristics of a Pasteurella sp. pathogenic for pond-cultured Ayu

During the late spring to the midsummer of 1971, an epizootic occurred among pondcultured Ayu, Plecoglossus altivelis, in Tokushima Prefecture. The disease was characterized by the diposition of white spots on the liver. The etiological agent was isolated from white spots on the liver and the kidney. The organisms were gram-negative, non-motile, polarly stained rods, and usually 1.0 to 3.0 by 0.3 to 0.5μ in size. On BHI agar, colonies doveloped within 24 hours at 25°C, and were uniformly round 1 mm or less in diameter. Growth was observed on MACCONKEY agar, ENDO agar, and ARAKAWA modified agar. Glucose, furactose, galactose, saccharose, maltose, dextrin, cellobiose, and salacin were fermented anaerogenically by the organism, whereas arabinose, xylose, mannose, trehalose, mannitol, and sorbitol were not attacked. Indole, H2S, acetyl methyl carbinol, methyl red, nitrate reduction were negative. Oxidase and catalase were positive. Because of its polar-staining and physiological reactions, the organism fits best in the genus Pasteurella. The isolate was found to be not identical to any formally established species. We propose that it be identified as Pasteurella plecoglosacida sp. nov.