Sponges are filthy! I wouldn't use a sponge even if I didn't have CF. I never use the sponge in our break room at work or any of the dishes that it touches. I actually bring my own dishes to work (coffee cup, silver wear) and take them home everyday. At home I use a dish brush. It doesn't stay wet as long as a sponge does. When I am done using it I dip it in an all purpose cleanser with bleach and every time I run the dish washer the brush is in there. I replace it about once a month.