Food handlers for sure, must always wash hands after using the restroom. This is to prevent contamination via fecal matter contact with the food you are to be handling, from several agents (E Coli, Colistiridium Deficile (C. Dif), Hepatitis A, and Norovirus to name a few.)
Additionally anytime you return to the kitchen and before you start handling food you should always wash your hands before handling the food. I'll also do you one better by saying you should at least run your hands before starting or touching any other dish.