| Summary: | In the present investigation we have studied 260 presumed Vibrio anguillarum isolates from a wide range of habitats, ,using a combination of eight different typing methods. The aims of the study were to investigate the diversity of V. anguillarum , as indicated by the use of combined typing, and to determine if strains with identical or similar characteristics were present in certain geographical locations, or in certain fish species. We also present a simple numerical method to analyse data obtained from combined typing.Two hundred and sixty isolates named as V. anguillarum from various fish species, rotifers, Artemia , water and sediment were subjected to the following eight assays: Species identification using ribotyping and the BIOLOG GN plates, subtyping using determination of outer membrane profiles, plasmid typing, serotyping, determination of lipopolysaccharide profiles and biotyping with API 20E, and biochemical fingerprinting with the PhenePlate system.The diversity among all isolates, calculated as Simpson's diversity index (Di), varied between 0.19 (ribotyping), i.e. most isolates belonged to the same type, and 0.98 (PhP), i.e. most isolates different. Upon combination of all methods, where a difference between two strains in at least two methods was regarded as significant, a diversity of 0.92 was obtained. Isolates collected from fish showed lower diversity (Di = 0.89) than those collected from other sources (environment, rotifers, Artemia ) (Di = 0.98). The lowest diversities were found among isolates collected from rainbow trout ( Oncorhynchus mykiss ), salmon ( Salmo salar ) and turbot ( Scophthalmus maximus ). Isolates from close geographical locations were also less diverse than isolates obtained from more distant locations.We conclude that the diversity of V. anguillarum is high, as shown by the combined typing methods. However, it seems that strains with specific characteristics are associated with certain geographic areas, and also with certain fish species. This could only be detected by applying a combination of several typing methods. Our results emphasise the need to use several different typing methods for studies of bacterial diversity.
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