Atypical Aeromonas salmonicida isolated from diseased turbot (Scophtalmus maximus L.).

Atypical Aeromonas salmonicida were isolated from 3 outbreaks of disease among farmed turbot (Scophthalmus maximus L.) in 3 different farms, 1 from Norway (N1) and 2 from Denmark (DK1 and DK2). In all 3 cases, the incidence of disease and mortality was high and the main characteristic pathological finding was skin ulcers and septicaemia. The isolated bacteria were subjected to a thorough phenotypic and genotypic examination and comparison in the laboratory. All 3 isolates belonged to A. salmonicida but displayed some very different biochemical properties. However, the 2 Danish strains, DK1 and DK2 had identical ribotypes but different from that of N1, whereas the plasmid profiles of DK1 and N1 were identical but different from that of DK2. These observations emphasize the need for an improvement of our understanding of the taxonomy and epidemiology of atypical A. salmonicida.