Characterization of Edwardsiella Species Isolated from Cultured Fishes in Ehime, Japan

Shogo Harakawa, Hisato Takeuchi, Hidemasa Kawakami, Sonoko Shimizu, Tohru Mekata

One hundred sixty-four Edwardsiella specimens isolated from cultured fishes, red seabream Pagrus major, Japanese flounder Paralichthys olivaceus, thread-sail filefish Stephanolepis cirrhifer, greater amberjack Seriola dumerili and Japanese eel Anguilla japonica were analyzed by PCR for identification, and 124 of these isolates were examined using biochemical tests for characterization. Hundred and four strains from red seabream, three from Japanese flounder, and six from other fish species were identified as E. anguillarum, whereas one strain from seabream and 50 strains from flounder were identified as E. piscicida. Among the E. anguillarum strains, all strains from Japanese eel were motile and ornithine decarboxylase (ODC)-positive, whereas all strains from other fish species were non-motile and ODC-negative. The findings of this study reveal the existence of two distinct types of E. anguillarum differing in motility and ODC production. Susceptibility testing using nine antimicrobials (tetracycline, erythromycin, lincomycin, ampicillin, sulfamonomethoxine, florfenicol, thiamphenicol, oxolinic acid, and fosfomycin) showed that all strains were sensitive to fosfomycin, which had a relatively narrow range of minimum inhibitory concentrations compared to other drugs.

Fish Pathology

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