Etiological Studies on Bacterial Pseudotuberculosis in Cultured Yellowtail with Pasteurella Piscicida as the Causative Agent-I

On the Morphological and Biochemical Properties

Abstract

Since 1969, bacterial pseudotuberculosis has been associated with serious mortarity of cultured young yellowtails during the summer months in many yellowtail farms on the west coast of Japan. The disease is characterized by the deposition of greyish white bacterial colonies, each covering an area of approximately 0.5-1.0mm at innumerable sites in the spleen and the kidney.
The cultures isolated from spleen and kidney lesions were small Gram-negative rods. In some instances, cultures from spleens and kidneys yielded an almost pure growth of this organism on nutrient agar and on blood agar. The organism grew in tiny, non-haemolytic, dew drop-like colonies on nutrient agar at 25°C in 48 hours; there was no growth at 35°C. The colonies had a margarin-like consistency. The organism was non-motile displaying a fairly uniform morphology. Acid was produced in glucose, fructose, galactose and mannose; but on gas production was evident; there was no observable reaction in xylose, arabinose, rhamnose, saccharose, maltose, trehalose, mannitol, lactose, sorbitol, salicin and dulcitol. The organism did not utilize citrate and failed to grow in a potassium cyanide medium. It was catalase and oxidase positive. The organism was therefore identified as Pasteurella piscicida JANSSEN and SURGALLA (1968).