Comparative Genomics of Aeromonas Salmonicida Subsp. Salmonicida Reveals a High Level of Heterogeneity

Aeromonas salmonicida subsp. salmonicida is the etiologic agent of furunculosis, a disease affecting fish of the salmonid family. This disease has important deleterious effects worldwide and it is even more problematic in the Province of Québec (Canada) where about 95% of the fish farming is devoted to salmonids. This situation is urging us to gain additional information about the virulence and the genomics of A. salmonicida subsp. salmonicida and especially from the strains isolated in the Province of Québec.

A total of 9 strains carefully selected based on their phenotypic and genetic features have been sequenced using the pyrosequencing method. Isolates were from the Canadian Provinces of Quebec (5) and New Brunswick (1), the United-States (1), Norway (1), and Switzerland (1). Various types of DNA libraries (shotgun, paired-end of various size) were tested to facilitate the assembly of the genome after production of the sequence data.

The preliminary results of this project revealed that A. salmonicida subsp. salmonicida strains are more heterogeneous than suspected at the genomic level especially by the presence of genomic islands, prophages and large plasmids. In the future, it is mandatory to determine the exact contribution of these elements in the virulence of the bacterium.