Background: Aeromonas salmonicida is a major fish pathogen associated with mass mortalities in salmonid fish.
In the present study, we applied In Vivo Induced Antigen Technology (IVIAT), a technique that relies on antibodies
adsorbed against in vitro cultures of the pathogen, to a clinical isolate of A. salmonicida subsp. salmonicida.
Results: The results from IVIAT allowed identification of four proteins that were upregulated in the fish samples:
A UDP-3-O-acyl-N-acetylglucosamine deacetylase, an RNA polymerase sigma factor D as well as TonB and a hypothetical
protein. Subsequent investigations were performed using real-time PCR and cDNA synthesised from infected
spleen, liver and anterior kidneys. These confirmed that the transcription level of each of these genes was
significantly upregulated during the infection process compared to bacteria in vitro.
Conclusions: The present studied identified four genes that were upregulated during the infectious process and are
likely to play a role in the virulence of A. salmonicida. Because these are antigenic they might constitute potential
targets for the development of new vaccine as well as therapeutic agents.