Many dishwashers do not "heat" during wash cycle, only on dry cycle. Dishes are washed in hot water at the temperature the water tank is set at. The sponge does not get sterilized, and neither do the dishes. Best to run faucet until it is hot before turning dishwasher on.

I called Mfgr. of my dishwasher and was surprised to learn the water was not heated during the wash cycle.

To sterilize sponges, put soppy wet sponge on a plate and microwave for 3-5 minutes.

University of Florida News � Researchers: Microwave oven can sterilize sponges, scrub pads

Thanks for the tip, I used to put them in the microwave, then thought it was better to put them in the dishwasher.
I'll go back to microwaving them, thanks...