Are you kidding? If you have a compost bin, and have ever added food scraps such as tomatoes, potatoes, lettuce, etc........you have had mice both eating and pooping in your compost pile. That is just one of the reasons for turning, mixing and churning so the heat decomposes everything inside. Just look at mice poop as poop you didn't have to buy the feed to produce! lol
As for the micro-biology thing........I work at a university. I tell the micro-prof I go around licking door knobs to boost my immune system. He gags when I say it.....lol
If we know half of what we eat, we wouldn't eat. Have you ever seen the creatures that live in your eye brows? Just stop thinking and worrying about it. We have servived for thousand of years. A little mouse poop won't kill us now!