Recently I have learned to look at my sponges. Yes, sponges. I saw a study that stated there are around 10 million bacteria per square inch of a kitchen sponge and a million per square inch on a dish cloth. I believe it!
Sponges are things we use everyday and may forget to think about changing out. I encourage you to change them out! I change mine when they smell, or when they are super frayed, of course. But now I just replace my sponges on a regular basis. I check them about every two weeks.