Sousvide seafood for sushi
Sous vide is a method to bring the interior of a meat to a safe temperature before applying a quick sear to the outside.  The sear is purely for flavor and texture, not food safety.

Sushi grade fish is certified to have been processed (i.e. frozen, cut) in such a way that it's edible raw.  The interior of a sushi grade salmon steak should have minimal bacteria if properly handled after purchase and isn't left to sit unrefrigerated.

So, to answer your question, yes, you can sous vide the fish, but I see no benefit, not even destroy meaningful amounts of bacteria (because there shouldn't be much there to begin with).