is especially nasty stuff.
nihPubMed comprises more than 30 million citations for biomedical literature from MEDLINE, life science journals, and online books. Citations may include links to full-text content from PubMed Central and publisher web sites.
https://www.ncbi.nlm.nih.gov/pubmed/24657158
I agree that we overreact typically to the need to sanitize everything. It's healthy to have some bacteria in your life. But scientists seem pretty unified in what I've read that taking shoes off is a pretty good idea for your health.