Indentification and Determination of Toxin Genes of Vibrio Strains Caused Hemorrhagic Disease on Red Drum (Sciaenops ocellatus) by PCR Method.

Abstract

In this study, we isolated thirty strains of Vibrio from three different organs (brain, hemorrhagic site and digestive system) of Sciaenops ocellatus disease. The results showed that nucleotide sequences 16S rRNA region are highly, similar to those of V. alginolyticus , V. azureus , V. fluvialis and V. orientalis is published on Genebank, ranging from 98.05 to 100 %. The digestive system has the most common Vibrio strains ( V. alginolyticus , V. azureu s and V. fluvialis ). Thereout, We found 25/30 strains of Vibrio containing from 1 to 3 toxin genes. None of V. parahaemolyticus present. Six parameters were used to measure the DNA polymorphism of thirty-three homologous DNA sequences in this Vibrio bacteria population. The results indicated that, number of separate polymorphic sites (S), total number of mutant sites (Eta), number of haplotype (h), haplotype diversity (Hd), average number of nucleotide differences (k), nucleotide diversity (Pi) were 98 (S) 103 (Eta), 9 (h), 0.887±0.032 (Hd), 25.789 (k) and 17.980x10-3±0.003 (Pi), respectively (P < 0,05). The G+C content above 1434 sites positions of nucleotide sequences accounts for 0.542. The phylogenetic tree showed that these strains are divided into six groups. As observed, the appearance of isolated Vibrio on 3 organs of fish ( S. ocellatus ) hemorrhagic are V. azureus (27,67 %), V. alginolyticus (50 %), V. orientalis (6,67 %) and V. fluvialis (16,67 %). Through this result, we found that the diversity of Vibrio species that appeared on the red drum was used in the 16S rRNA region and the presence of toxin genes in these Vibrio species.