Vibrio coralliilyticus as an agent of red spotting disease in the sea urchin Strongylocentrotus intermedius

Abstract

The bacterium, Vibrio coralliilyticus, is well known as one of the main pathogens involved in coral bleaching; however, there have been no previous reports of this bacterium in sea urchins. In the current study, a dominant bacterium, Rb102, was isolated from the coelomic fluid of a sea urchin (Strongylocentrotus intermedius) with red spotting disease, at a farm in Dalian, Liaoning Province. The isolates were identified based on Gram staining, morphological observations, 16S rDNA phylogenetic tree analysis, identification of physiological and biochemical characteristics, drug sensitivity tests, and artificial infection experiments. The identification and isolation results showed Rb102 to be V. coralliilyticus. Artificial infection experiments showed that Rb102 could infect S. intermedius by injection, causing the typical red spotting symptoms of this disease; the strains isolated from the diseased sea urchins were of the same strain type. The results of the bacterial susceptibility tests showed that Rb102 was highly susceptible to gentamicin, neomycin, tetracycline, cefradine, and ofloxacin, but showed strong resistance to vancomycin, ceftriaxone, kanamycin, rifampicin, midecamycin, cefoperazone, ceftazidime, cotrimoxazole, and penicillin. The results of this study provide a reference for further study of the pathogenesis of V. coralliilyticus-induced erythema in sea urchins (S. intermedius) and its prevention and control.