RIBOTYPING OF AEROMONAS-SALMONICIDA SUBSP SALMONICIDA

A collection of 124 strains of the bacterial fish pathogen Aeromonas salmonicida subsp. salmonicida isolated from diseased salmonids in Denmark (n = 57), Norway (n = 28), Scotland (n = 20), and North America (n = 19) was characterized by ribotyping. For reference, the type strain NCMB 1102 was likewise examined. Digestion of total DNA with the enzymes EcoR1, HindIII and Sma1 resulted in 2, 1 and 5 ribotypes, respectively, with a total of 6 ribotypes in combination. The type strain NCMB 1102 belonged to the most common of the ribotypes, irrespective of the enzyme used. Although Danish and North American strains were genetically very homogeneous, Norwegian and Scottish isolates showed some genetic diversity. In general, ribotyping was not found to be applicable as an epizootiological typing system for A. salmonicida subsp. salmonicida due to low discriminatory power. Norwegian and Scottish strains contained a common Sma1 ribotype suggesting a connection between isolates from these 2 countries.