Pathogenicity of Motile and Non-motile Edwardsiella tarda to Some Marine Fish

We examined the pathogenicity of typical (motile) and atypical (non-motile) Edwardsiella tarda against three marine fish species : yellowtail Seriola quinqueradiata, Japanese flounder Paralichthys olivaceus and red sea bream Pagrus major. Through intraperitneal injection, all provided strains (five typical and two atypical strains) showed pathogenicity to yellowtail and Japanese flounder, while only the atypical strains showed pathogenicity to red sea bream. In immersion challenges using each one selected strain, Japanese flounder was killed only by the typical E. tarda, while red sea bream was killed only by the atypical E. tarda. The results show the apparent difference in the pathogenicity between typical and atypical E. tarda.