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

Abstract

Based on the nucleotide sequences of 16S rDNA, Japanese isolates of atypical Aeromonas salmonicida from 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 goldfish Carassius auratus had sequences identical to those from goldfish in the USA and formed the first group. Isolates from Japanese eel Anguilla japonica and marine fishes (greenling Hexagrammos otakii, Japanese flounder Paralichthys olivaceus, shotted halibut Eopsetta grigorjewi and Schlegel's black rockfish Sebastes schlegeli) formed the second group, and had identical sequences with those of A. salmonicida subsp. achromogenes JCM7875T, A. salmonicida subsp. masoucida JCM7873T and A. salmonicida subsp. smithia ATCC49393T. The third and fourth groups composed of isolates from coloured carp Cyprinus carpio and common carp C. 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.