When I use my reuseable bag, I always have a plastic bag on the inside to prevent bacterial or mold growth. There have been many articles online about how many reuseable bags have been tested for various issues and there have been such things as ecoli found in the bags!
This would happen more with reusebale bags at grocery stores, like with meats being carried in them, etc., but it can happen with many other products too...such as with dairy products, which CVS sells. Just a heads up folks...keep those bags clean! Many reuseable bags can't be washed in the washing machine due to the materials they are made of too. If that be the case, maintain your bag by using a plastic one inside...which you can reuse too
Here's a link to an informative article...
Reusable grocery bags found to be full of bacteria