The identification and determination of toxin genes of Vibrio strains causing hemorrhagic disease on red drum (Sciaenops ocellatus) using PCR

Abstract

AbstractData were collected from 30 strains ofVibrioand sampled on different organs (brain, hemorrhagic site and digestive tract) ofSciaenops ocellatusinfection. The results showed that the nucleotide sequences 16S rRNA region are highly similar to those ofV. alginolyticus,V. azureus,V. fluvialis, V. natriengensandV. orientalis,which were published on Genbank and other, ranging from 98.05 to 100%. The digestive tract has the most commonVibriostrains (V. alginolyticus[16]V. azureus [7] andV. fluvialis). Thereout, 25 of 30 strains ofVibriocontained 1 to 3 toxin genes, exceptV. parahaemolyticus. Six parameters were used to measure the DNA polymorphism of 33 homologous DNA sequences in thisVibriobacteria 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 17.980 × 10–3 ± 0.003 (Pi), respectively (P < 0,05). The G + C content above 1434 sites positions of nucleotide sequences accounted for 0.542. The phylogenetic tree showed that these strains are divided into six groups. As observed, the appearance of isolatedVibrioon 3 organs of fish (S. ocellatus) hemorrhagic areV. azureus(27,67%),V. alginolyticus(50%),V. orientalis(6,67%) andV. fluvialis(16,67%). Through this result, we found that the diversity ofVibriospecies that appeared on the red drum was used in the 16S rRNA region and the presence of toxin genes in theseVibriospecies.