For anyone who is a germaphobe this is going to cause panic. If you leave your toothbrush in the bathroom (like most normal people) you’re going to end up with someone else’s bacteria on your toothbrush it’s unavoidable. This becomes even truer when more than one person leaves their toothbrushes in the same bathroom. A study done at a University found out that more than 60% of students who shared a bathroom had someone else’s bacteria on their toothbrush. But before you panic, there haven’t been any dental bacterial related deaths so you will probably be fine.
More on the study can be found here.