I was taking Microbiology in college. One of the projects was to go around the school and take samples of different areas, grow them out, and identify the colonies using a Bergey's manual.
I took samples of toilet seats, handle to the bathroom, cafeteria tables, cafeteria tray, different floor areas, all kinds of places.
I was shocked that the most harmful and highest quantity of bacteria were on the cafeteria trays and secondly the bathroom door handle. The toilet seat had almost none.