ATYPICAL AEROMONAS-SALMONICIDA INFECTION IN CULTURED MARINE FISH

Bacteria were isolated from diseased marine fishes (greenling Hexagram mos otakii, Japanese flounder Paralichthys olivaceus and Schlegel's bl ack rockfish Sebastes schlegeli) cultured in Oita Prefecture. Irrespec tive of sources, these bacteria showed the same characteristics. They were Gram negative, facultatively anaerobic and non-motile rod. Cytoch rome oxidase, catalase, brown pigment and auto-aggregation were positi ve. Growth at 37 degrees C and O/129 sensitivity were negative. The ba cteria exhibited positive reaction against an anti Aeromonas salmonici da subsp. salmonicida serum. The isolates were identified as atypical A. salmonicida on the basis of these characteristics. Intraperitoneal injection confirmed the virulence of the bacterium to Japanese flounde r. This atypical A. salmonicida is thought to be the causative agent o f the disease.