Control Methods for Spotting Disease of Sea Urchin Strongylocentrotus intermedius

To prevent a loss of cultured sea urchin Strongylocentrotus intermedius caused by spotting disease, effects of treatments by low temperature, disinfectants, drugs, ultraviolet irradiation, and oxidant on the control of growth and pathogenicity of the causative bacterium, Flexibacter sp. 12-N using a representative strain were examined. Pathogenicity of the bacterium was not exhibited in the experimental infection at 15°C, which was near the lowest growth temperature of the bacterium. The bacterium showed high sensitivity to erythromycin, oleandomycin and lincomycin, but was resistant to kanamycin and nalidixic acid. Susceptibilities of the bacterium to ultraviolet irradiation and oxidant were high, similar to those reported for fish pathogenic bacteria. Moreover, among the eight disinfectants tested in vitro, treatment with a 300 ppm hydrogen peroxide for 5 min at 15°C was found to disinfect significantly the bacterium without any injurious effect to the sea urchins.