Phylogenetic intrarelationships of atypical Aeromonas salmonicida isolatedin Japan as determined by 16S rDNA sequencing

Based on the nucleotide sequences of 16S rDNA, Japanese isolates of atypica l Aeromonas salmonicida from different fish species can be divided into fou r groups; isolates from each species of fish (including fish reared in simi lar culture conditions) always belonged to the same group. Isolates from go ldfish Carassius auratus had sequences identical to those from goldfish in the USA and formed the first group. Isolates from Japanese eel Anguilla jap onica and marine fishes (greenling Hexagrammos otakii, Japanese flounder Pa ralichthys olivaceus, shotted halibut Eopsetta grigorjewi and Schlegel's bl ack rockfish Sebastes schlegeli) formed the second group, and had identical sequences with those of A. salmonicida subsp. achromogenes JCM7875(T), A. salmonicida subsp. masoucida JCM7873(T) and A. salmonicida subsp. smithia A TCC49393(T). The third and fourth groups composed of isolates from coloured carp Cyprinus carpio and common carp C. carpio, respectively. This indicat es that the expansion of ulcerative disease in recent years is caused by st rains which have phyletic lines different from goldfish isolates.