Atypical Aeromonas salmonicida infection in cultured marine fish.
Bacteria were isolated from diseased marine fishes (greenling Hexagrammos otakii, Japanese flounder Paralichthys olivaceus and Schlegel's black rockfish Sebastes schlegeli) cultured in Oita Prefecture. Irrespective of sources, these bacteria showed the same characteristics. They were Gram negative, facultatively anaerobic and non-motile rod. Cytochrome oxidase, catalase, brown pigment and auto-aggregation were positive. Growth at 37°C and O/129 sensitivity were negative. The bacteria showed positive reactions against an anti-Aeromonas salmonicida 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 flounder. This atypical A. salmonicida is thought to be the causative agent of the disease.