2.9.1. Determination of LD50 of A. salmonicida infection on S. senegalensis
Bacteria were grown overnight in TSB supplemented with 1.5%
NaCL, at 25 °C. Bacterial cells were centrifuged and washed twice with
PBS. The bacterial suspension was adjusted to about 109 CFU mL−1
with PBS.
Determination of Lethal Dose (LD50) of A. salmonicida infection on
S. senegalensis was performed in order to establish the concentration
of A. salmonicida able to cause death in about 50% of juvenile fish in
72 h. A fresh culture of A. salmonicida was produced and then resuspended
in PBS in order to reduce the introduction of organic matter in
the tanks. The control tank was inoculated with PBS without any addition
of bacteria. Bacterial suspension was added to the water and the juvenile
fish of the four tanks employed were maintained under optimal
growth conditions. Fish mortality was determined by visual inspection
every 12 h. Three independent assays were performed in different
dates.