Characterization of strains of Vibrio splendidus and V. tapetis isolated from corkwing wrasse Symphodus melops suffering vibriosis

Abstract

Two vibrio bacteria pathogenic to the corkwing wrasse Symphodus melops were isolated. Vibriosis-inducing strain LP1 was isolated as the dominanting bacterium in kidney samples of dead and moribund wrasse from a population suffering vibriosis and high daily mortality in 1998 on the Norwegian west coast. The other vibriosis-inducing strain, LP2, was isolated from wrasse captured the following year. Re-infection experiments have confirmed that these strains cause vibriosis in corkwing wrasse. Both strains were typical vibrios sharing the traits of fermentative Gram-negative curved rods with motility and a positive oxidase reaction. Detailed biochemical and genetic characterisation revealed a close affiliation to known species of the marine environment. The first isolate, LP1, is a form of the ubiquitous seawater organism Vibrio splendidus, while the second isolate, LP2, is closely related to V. tapetis (previously only known as the brown ring disease agent in clams). Identification of the new wrasse pathogens V. splendidus LP1 and V. tapetis LP2 is facilitated by break points observed in this study.KEY WORDS: Vibrio · Wrasse · Vibriosis · Taxonomy · Phylogeny Resale or republication not permitted without written consent of the publisherDis Aquat Org 53: [25][26][27][28][29][30][31] 2003 experienced although held under favourable conditions in the laboratory. As with the first group, bacteriological examinations were carried out with the intention to find a causative agent. Cultivation of kidney samples of moribund and dead fish indicated bacterial aetiology. Isolation yelded 1 dominant strain from both groups. The strain LP1 isolated from the 1998 group was tentatively assigned to the genus Vibrio . The strain dominating the samplings from 1999 was numbered LP2.The purpose of the present study was to characterise strains LP1 and LP2 isolated from dead and moribund corkwing wrasse at the biochemical, serological and genetical level and to identify them to species level. MATERIALS AND METHODSExperimental fish. Corkwing wrasse Symphodus melops were captured by fish trap near Bergen (Norway) in the autumns of 1998 and 1999 by a local fisherman. This method allowed wild wrasse of 45 ± 9 g to be swiftly collected for transport to the Institute of Marine Research where approximately 400 individuals were stocked in flow-through storage tanks (1 m deep × 2.5 m i.d.) held at 13 ± 0.5°C. The storage tanks were provided with artificial seaweed and plastic tubes for shelter. The fish were fed krill to satiation every second day (1998 group) or every day (1999 group). After approximately 4 wk in the tanks, a general loss of appetite was noticed and the fish started to die. From each group, kidney samples from 20 moribund and dead fish were examined for the presence of bacteria by cultivation.Bacterial isolation and cultivation. Before necropsy, the wrasse were disinfected with 70% ethanol. Posterior kidney samples were inoculated directly into nutrient blood agar (Oxoid, Basingstoke, UK) supplemented with 5% sheep b...

Vibrio tapetis from wrasse used for ectoparasite bio-control in salmon farming: phylogenetic analysis and serotyping

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Seasonal variation in parasite infection patterns of marine fish species from the Northern Wadden Sea in relation to interannual temperature fluctuations

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