Identification and characterization of Vibrio bacteria isolated from fish and shellfish in Vietnam

A taxonomic relationship of thirty one Vietnamese bacterial isolates from different fish and shellfish together with twenty two reference strains was investigated by Euclidean distance with unweighted average linkage clustering. Comparison based on fourty seven phenotypic characters showed that these isolates mainly clustered in six groups of which four were equated with the well known Vibrio species, V. alginolyticus, V. harveyi, V. cholerae and V. mimicus. For the remaining two groups comprising twelve isolates, it was more difficult to establish any relationship with known species when compared with reference strains. Strains were also subjected to rRNA gene restriction pattern analysis (ribotyping), using Mlu I as restriction enzyme. Eleven ribotypes were detected among the Vietnamese isolates. Similarity of ribotyping patterns between strains supported the phenotypic identification. Twenty-eight strains were found to carry at least one plasmid and 12 different sized plasmids were detected ranging from less than 2 to 140 kb. The two Vibrio spp. groups performed high phenotypic and genotypic similarity within each group but were only remotely related with the reference strains. The evidence suggest that these strains may represent new Vibrio species.