Relative abundance of Aeromonas salmonicida subsp. s almonicida in spleen of rainbow trout at various time-points. The relative bacterial number was calculated by comparing the number of copies of bacterial 16S rRNA to that of the host’ β-actin. The fish had been infected intra-peritoneally with a solution of 103 CFU of A. salmonicida in 0.9 M phosphate buffered saline. Fish were sampled at 1, 6, 12, 48 hours and 1 week post-infection. Each value represents the mean of triplicate independent biological samples and error bars indicate standard deviation.