Edwardsiella tarda (Paracolobactrum anguillimortiferum) Associated with Pond-Cultured Eel Disease

Abstract

Morphological and biochemical characteristics of 22 strains of an enteric bacterium isolated from diseased pond-cultured eels in Shizuoka Prefecture in 1972 were examined. These organisms were gram-negative, peritrichously flagellated rods. They gave negative oxidase reaction, utilized glucose fermentatively in Hugh-Leifson's medium and reduced nitrate to nitrite. Some distinguishing features of the organisms were the produc-tion of hydrogen sulfide and indol, positive to methylted test, negative to Voges-Proskauer test, no growth on Simmons' citrate agar, growth on Christensen's citrate agar, decarboxi-lization of lysine and ornithine, and utilization of fructose, galactose, mannose, maltose, and glycerol (Table 1). All of the strains examined were sensitive to dihydrostreptomycin and kanamycin, but some of them were resistant to chloramphenicol, tetracycline and colistin (Table 2). The above properties suggest that the organism should be identified as Edwardsiella tarda, with which Paracolobactrum anguillimortiferum is thought to be synonymous.