Vibrio viscosus and Vibrio wodanis are recently described species of psychrotropic bacteria that have been found associated with a disease called ' winter ulcer ', affecting salmonid fish reared in saline water in Norway, Iceland and recently in Scotland. V. viscosus and V. wodanis strains initially isolated from fish in Iceland and Norway were subjected to characterization using biochemical tests, SDS-PAGE of whole-cell proteins and a novel DNA fingerprinting method, amplified fragment length polymorphism (AFLP). The V. viscosus strains isolated from diseased fish grouped into homogeneous subgroups according to geographical origin and challenge experiments revealed that representatives of these groups are virulent. The results revealed that the V. wodanis strains are heterogeneous genotypically and phenotypically. Sequencing of almost complete 16S rRNA genes of V. viscosus and V. wodanis revealed that V. viscosus showed a 991 % sequence similarity to Moritella marina and V. wodanis showed a 988 % sequence similarity to Vibrio logei CIP 103204. A reclassification of Vibrio viscosus as Moritella viscosa comb. nov. is proposed.

No abstract

No abstract

Cod, Gadus morhua L., of wild origin, were reared at different temperatures for 12 months. During this period, moribund and newly dead fish were examined and samples collected for bacteriology and histopathology. Atypical Aeromonas salmonicida was isolated from 10 individuals reared at or above 7 °C. The isolates were homogeneous with respect to biochemical and antibiogram characters and similar to the ssp. achromogenes National Collection of Industrial and Marine Bacteria, UK, type strain 1110 and reference strains that have been isolated from salmonids and haddock in Iceland. Histopathological analysis of the naturally infected cod showed typical ulceration associated with atypical A. salmonicida infection and also widespread granulomatous formations. One‐year‐old cod of farmed origin, kept at 9 °C, received intraperitoneal or intramuscular injection with different doses of atypical A. salmonicida, isolated from the above wild cod. Mortalities were monitored for 28 days and the LD50 calculated. The route of bacterial injection influenced the mortality rate and LD50 value and affected, to some extent, the pathological changes observed and humoral immune parameters. Pathological changes, including haemorrhage, early stages of granuloma formation and necrotic changes, were seen in several organs. Infection appeared to induce non‐specific antibody activity against trinitrophenyl (TNP)‐haptenated protein and may have activated the complement system. Specific antibody response against atypical A. salmonicida was not detected.

No abstract