THE DETECTION OF FISH PATHOGEN VIBRIO-ANGUILLARUM IN WATER AND FISH USING A SPECIES-SPECIFIC DNA-PROBE COMBINED WITH MEMBRANE FILTRATION

The marine bacterium Vibrio anguillarum causes disease in fish worldwide and is particularly devastating in aquaculture. Little is known about the ecology of V. anguillarum in the environment and how this may relate to the pathogenicity of this organism. Combining membrane filtration and a species-specific DNA probe, culturable V. anguillarum cells were detected in water from three habitats and in chinook salmon (Onchorynchus tshawytscha) tissue samples. Results show that different marine habitats have a marked effect on cell numbers and that water temperature may play a role in the culturability and distribution of V. anguillarum. Vibrio anguillarum was detected from the gills of salmon within 24 h of transfer of fingerlings from freshwater to seawater, with cell numbers reaching a concentration of 1.9 x 10(2) cells g(-1) tissue 28 days post transfer. Vibrio anguillarum cell numbers were low in the colon throughout the study, and V. anguillarum was not detected in healthy kidney samples. The methodology reported in this paper allows the accurate quantification of culturable V. anguillarum cells and has allowed a preliminary study of the ecology of this species.