Rapid detection of important bacterial pathogens in Atlantic cod Gadus morhua through loop-mediated isothermal amplification reaction

Loop-mediated isothermal amplification (LAMP)-based assays were developed for the detection of Vibrio anguillarum O2_b and Aeromonas salmoniida, the causative agents of vibriosis and atypical furunculosis in Atlantic cod, Gadus morhua, respectively. Primers targeting the flanking regions of the genes: amiB in V. anguillarum O2_b and gyrB in A. salonicida were used for the LAMP reaction and were found to be highly specific for each pathogen. The detection limit of the assay was 10 pg and 1 pg of bacterial DNA ml-1 for V. anguillarum and A. salmonicida, respectively. However, the sensitivity of the reaction in detecting V. anguillarum decreased by 3 log dilution and 1 log dilution for A. salmonicida in the presence of mucus as inhibitor. Nevertheless, the assay can be potentially used as a direct and non-destructive method to detect these pathogens in the fish, thus making the assay less time consuming. These results suggest that LAMP is a specific and sensitive molecular method to diagnose vibriosis and atypical furunculosis in Atlantic cod and will be helpful for routine surveillance programs in aquaculture systems.