We run our dishwasher at least once each day, and it still sometimes
acquires a nasty odor. I don't know the cause. Perhaps it is from food
residuals in the garbage grinder output - every dishwasher has a
mechanism for disposing solids in the outflow.

When we detect the odor, we treat it by placing a cup filled with white
vinegar on the upper rack, and running the machine cycle. That usually
eliminates it.

There are also cleaning products specifically designed to deodorize and
clean dishwashers. We have not tried them.

--
Julian Vrieslander