Have not been keeping my toothbrushes in the bathroom for years now. Not directly because of those tests on faecal bacteria. But that was a reason not to have them back in the bathroom.
I lived in houses with no toilet in the bathing room most of my life. I liked that a whole lot better. Alas, that is not the case in this house.
The issue is; just how "airborne" can things like E. coli become in an environment of super high humidity.
In our house both toilets are in little cubby spaces and I have taught my kids to always close the toilet before flushing. NONE of this typical bullshit about just putting the seat down for the girls, which seems to be the first fight between a man and a woman attempting to co-habitate. I have taught everyone, including MY WIFE to close the damn thing entirely before flushing, not just continue to expect the seat to be down every time she goes in there. It should always be closed!
Not sure how much it helps, but at least some of the "spray" from flushing is not sent directly into the air. I think the little cubby space enclosed around the toilets helps as well.
Seriously, though, how long can E. coli live in a "room temperature" environment, assuming that it has not hitched a ride on a warm, moist, filthy human being? I suspect, much longer than we would be comfortable knowing.