Abstract
Based on the nucleotide sequences of 16S rDNA, Japanese isolates of atypicalAeromonas salmonicidafrom different fish species can be divided into four groups; isolates from each species of fish (including fish reared in similar culture conditions) always belonged to the same group. Isolates from goldfishCarassius auratushad sequences identical to those from goldfish in the USA and formed the first group. Isolates from Japanese eelAnguilla japonica and marine fishes (greenlingHexagrammos otakii, Japanese flounderParalichthys olivaceus, shotted halibutEopsetta grigorjewi and Schlegel's black rockfish Sebastes schlegeli) formed the second group, and had identical sequences with those ofA. salmonicidasubsp.achromogenes JCM7875T, A. salmonicida subsp. masoucida JCM7873TandA. salmonicida subsp. smithia ATCC49393T. The third and fourth groups composed of isolates from coloured carpCyprinus carpioand common carpC. carpio, respectively. This indicates that the expansion of ulcerative disease in recent years is caused by strains which have phyletic lines different from goldfish isolates.
