Characteristics of a Pseudomonas sp. from an Epizootic of Pond-Cultured Eels (Anguilla japonica)

Abstract

Outbreaks of a new bacterial disease ‘Sekiten-byo’ (red spot disease) caused mass mortalities among pond-cultured eel populations in both Shizuoka and Tokushima prefectures during late spring to early summer in 1971. A remarkable petechial hemorrhage in the body surface appeared to be the sole characteristic symptom of the disease. Generally, a great mumber of bacteria were found in the blood of moribund fish.
The causative organism is a Gram-negative, non-acid-fast, nonsporing rod with a single polar flagellum, measuring about 2×0.4μ. The bacilli have metachromatic granules. Growth of the bacterium on a nutrient agar medium was rather slow. Colonies after 72 hr incubation at 25°C on nutrient agar were uniformly round, 1mm or less in diameter, glistening, light grey, entire, convex, translucent and vicid. Mortility of the organism varied with incubation temperature.
Because of the production of oxidase, nonsensitiveness to vibriostat 0/129 and inability both to attack glucose and to produce diffusible pigment, the bacterium is placed in the genus Pseudomonas, group III or IV. The bacterium was found to be not identical in its biochemical characteristics and pathogenicity to fish to any formally established species of the genus Pseudomonas, and thus we suggest that it be identified as Pseudomonas anguilliseptica sp. nov.