Vibrio Vulnificus Biogroup 2: New Biogroup Pathogenic for Eels

Clinical and nonclinical isolates of the lactose-positive Vibrio vulnificus were compared with Vibrio strains isolated from lesions on eels (Anguilla japonica) cultured commercially in Japan. Strains were compared phenotypically and antigenically, for pathogenicity to mice and eels, and for genetic relatedness. The strains isolated from diseased eels differed phenotypically from the original species description of V. vulnificus in that they were negative for indole production, ornithine decarboxylase activity, growth at 42 degrees C, and acid production from mannitol and sorbitol. No relationship between the surface antigens of V. vulnificus strains from environmental and clinical sources and the strains from diseased eels was observed. Typical V. vulnificus strains and the eel isolates were pathogenic to mice; however, only those strains originally isolated from diseased eels were found to be pathogenic to eels. Results of DNA-DNA competition experiments revealed that there was greater than 90% relative reassociation between clinical and nonclinical V. vulnificus and strains from diseased eels. Based on the results of the DNA-DNA competition experiments, we conclude that the strains isolated from diseased eels were V. vulnificus; however, the differences in phenotypic characteristics and eel pathogenicity indicated that these strains represent a different biogroup. Therefore, we propose that strains phenotypically similar to the type strain of the species (ATCC 27562) be classified as V. vulnificus biogroup 1 and the strains phenotypically similar to those isolated from diseased eels be classified as V. vulnificus biogroup 2 represented by the reference strain ATCC 33148.