Aim: The major objective of the present study was to clarify genetic relationship of isolates of Edwardsiella ictaluri in Japan, which was first found from ayu Plecoglossus altivelis in Japanese rivers in 2007.
Methods and results: Ten isolates of Edw. ictaluri in 2007-2008 from ayu and the 1 isolate from bagrid catfish Pelteobagrus nudiceps in Japan were subjected to amplified-fragment length polymorphism (AFLP) analysis. The strains isolated from catfish in United States (ATCC strains) or Indonesia were used as reference strains. The AFLP profiles were all the same among the isolates from Japan, while the polymorphic DNA bands were observed among the strains from United States or Indonesia. The isolates from Japan and Indonesia constituted a genogroup different from the ATCC strains on a dendrogram constructed from the AFLP profiles.
Conclusion: No DNA polymorphisms were found among Japanese Edw. ictaluri isolates.
Significance and impact of the study: A single clonality of the Edw. ictaluri isolates in Japan suggests the single source of the organism, and the infection in ayu is in the early stage of epidemics.