Genetic diversity of the fish pathogen Aeromonas salmonicida demonstrated by random amplified polymorphic DNA and pulsed-field gel electrophoresis analyses

The current taxonomy of Aeromonas salmonicida includes 4 subspecies. A. sal monicida subsp. salmonicida is associated with salmonid furunculosis, and A . salmonicida subsp, achromogenes, A. salmonicida subsp. masoucida, and A. salmonicida subsp. smithia are strains that show variation in some biochemi cal properties. This classification does not readily encompass isolates fro m a wide range of fish hosts currently described as atypical A. salmonicida . This study examined 17 typical strains, 39 atypical strains and 3 type A. salmonicida subspecies strains for genetic similarity using the random amp lified polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) t echniques. On the basis of RAPD- and PFGE-derived profiles, similarity matr ices and dendrograms were constructed. The results showed that species A. s almonicida constituted a genetically heterogeneous group of strains, encomp assing within an homogeneous or clonal lineage comprised solely of typical strains and the A. salmonicida subsp, salmonicida type strain.