Why Sharing a Bathroom with Someone is Gross
At a meeting of the American Society for Microbiology in Louisiana, a study presented found that about 60% of the toothbrushes collected from a sample, where people shared bathrooms, had fecal matter on it (other people’s). When people store their toothbrushes on a counter, the toothbrush is exposed to material and microorganisms from other occupants who use the bathroom. This study does not suggest that people should store their brushes in closed containers, a practice that can encourage bacterial growth by preventing the bristles to dry out in between uses.
The concern from the study is not whether or not there is fecal matter on toothbrushes, but it is about cross contamination of bacteria between people. When exposed to bacteria that is not part of your natural flora, there is a higher chance that those species may be pathogenic.
It is my opinion that in order to avoid this phenomenon good hygiene practices should be practiced. If possible, have your own bathroom or choose a bathroom where the toilet is in a separate room from the sink with a door. The American Dental Association recommendations for toothbrush care are as follows:
1) Do not share toothbrushes
2) Do no cover toothbrushes or store them in closed containers
3) Replace toothbrushes every 3 months
4) Rinse brushes thoroughly after brushing.