Regarding the early cellular response to P. salmonis, ROS- and N-oxide-forming proteins were identified in infected SHK-1 cells (Table 1), which is in agreement with the respiratory burst response to pathogen infection in fish [36], although the enzyme NADPH-oxidase (NOX2), which is pivotal to the respiratory burst, was not found at any infection stage. This evidence concerns the gene FMO5 and infection.