The agitator bars are plastic - they're unlikely to be smelly.
What you smell is very probably bugs in the pipes - particularly if you use 30 degree washes.
You might consider a really hot wash with some vinegar instead of detergent - to kill off the organisms living inside.
Consider also that the smell may be from the house drains - this was the cause of our smelly washer when we had our last pong incident.
Good luck..., June 2015