Do you see a black fungus on the seal around your dishwasher door or inside your dishwasher? It may be Exophiala dermatitidis, a fungus that likes high heat and is resistant to most detergents. Scrub it away with a paste of vinegar and baking soda. While you're in the dishwasher, pour a couple of cups of vinegar in the bottom and run a cycle to kill other tough germs.