The show Mythbusters did this in 2004! The episode is called “Toothbrush Surprise” because they were so surprised when the control toothbrushes away from the bathroom had fecal bacteria right from the start.

They talked to a microbiologist, who said fecal coliforms are impossible to avoid. Farting in jars won’t help, it’s already everywhere.

Keeping the toothbrush in a different room is provably completely pointless. It’s superstition.

Ironically, keeping it in the open in the kitchen is likely worse than keeping it in a cabinet in the bathroom.