Application of the rpoS gene for the detection of Vibrio anguillarum in flounder and prawn by polymerase chain reaction

Vibrio anguillarum , an opportunistic fish pathogen, is the main species responsible for vibriosis, a disease that affects feral and farmed fish and shellfish, and causes considerable economic losses in marine aquaculture. In this study, we used polymerase chain reaction (PCR) to detect V. anguillarum . PCR specificity was evaluated by amplifying the rpoS gene, a general stress regulator, in six strains of V. anguillarum and 36 other bacterial species. PCR amplified a species-specific fragment (689 bp) from V. anguillarum . Furthermore, the PCR assay was sensitive enough to detect rpoS expression from 3 pg of genomic DNA , or from six colony-forming units (CFU) mL^?1 of cultured V. anguillarum . However, the assay was less sensitive when genomic DNA from the infected flounder and prawn was used (limit of detection, 50 ng and 10 ng g^?1 tissue, respectively). These data demonstrate that PCR amplification of the rpoS gene is a sensitive and species-specific method to detect V. anguillarum in practical situations.