Molecular Characterization of Vibrio Harveyi in Diseased Shrimp

The objective of this study was to characterize Vibrio harveyi phenotypically and by molecular methods. A total number of 420 shrimp post larvae samples were collected, 280 samples of diseased cultured shrimp and 140 samples of apparently healthy marine shrimp. The samples were subjected to bacteriological examination. Thirty three (11.7%) of cultured shrimp samples and 4 (2.8%) of marine shrimp samples were phenotypically positive for V. harveyi. Species - specific gene (toxRgene) and two virulence associated genes (vhh -Vibrio harveyi haemolysin, and partial hly- haemolysin gene) were investigated using conventional PCR. This study proved that using of partial haemolysin gene in molecular characterization of V. harveyi is the fastest and most accurate method to identify all isolates of V. harveyi (highly pathogenic, moderately pathogenic and non-pathogenic strains) due to the presence of a single copy of haemolysin gene encoded in all isolates, although it is not in the same locus in the genome.