Good news:The bacteria that live on your toothbrush reflects your mouth — not your toilet. After studying microbial communities that live on bristles from used toothbrushes, researchers at Northwestern University found that those communities resembled microbes commonly found in the mouth and on the skin. This was true no matter where the toothbrushes were stored, including shielded behind a closed medicine cabinet door or out in the open at the edge of a sink.
The study's senior author, Erica Hartmann, was inspired to conduct the study after hearing concerns that flushing a toilet could generate a cloud of aerosol particles. She and her team fondly called their study “Operation Pottymouth”.
"I'm not saying you can't get toilet sprays on your toothbrush when you flush the toilet," Hartmann said. “But based on what we saw in our study, the vast majority of microbes on your toothbrush probably came from your mouth.”
Collect samples
To get toothbrushes for the study, Hartmann's team launched the Toothbrush Microbiome Project, in which people were asked to submit their used toothbrushes, along with associated metadata. Hartmann's team then extracted DNA from the bristles to investigate the microbial communities found there. They compared these communities to those of the Human Microbiome Project, an NIH initiative that identified and cataloged microbial flora from various parts of the human body.
“We found that the microbes on toothbrushes have a lot in common with the mouth and skin and very little in common with the human gut.”
"Your mouth and your gut are not separate islands," Hartmann added. “There are some microbes that we find both in the human gut and in the mouth, and those microbes can be found on toothbrushes. But again, they probably come out of your mouth.”
Clean mouth, clean toothbrush
During the study, Hartmann's team examined how many different types of microbes lived on the toothbrushes. They found that people with better oral hygiene, who flossed regularly and used mouthwash, had toothbrushes with less diverse microbial communities.
"If you practice good oral hygiene, your toothbrush will also be relatively clean," Hartmann said. “But it's a small difference. It's not that people who regularly floss, brush, and use mouthwashes don't have microbes and those who don't have a whole lot. There is just a little less diversity in toothbrushes from people who do all those things.”
The researchers also found that microbes from toothbrushes from people with better oral hygiene had slightly more antimicrobial resistance genes. Hartmann said microbes with these genes did not match the human body and probably came from air or dust in the bathroom.
Hartmann emphasizes that you don't have to be alarmed by microbes that live on your toothbrush. Unless your dentist advises otherwise, people should not reach for antimicrobial toothpastes and toothbrushes.
"By using antimicrobials, you don't just get rid of microbes," Hartmann said. “You drive the surviving microbes toward antimicrobial resistance. In general, ordinary toothpaste is sufficient for most people.”
