Bacteria living on the toothbrush reflect oral hygiene, not toilet spray

The good news is that the bacteria on your toothbrush reflect your mouth – not your toilet.

After studying the microbial communities living on the bristles of used toothbrushes, researchers at Northwestern University found that these communities correspond to microbes commonly found in the mouth and on the skin. This was true regardless of where the toothbrushes had been stored, including protected behind a closed medicine cabinet door or in the open over the edge of a sink.

Lead author of the study, Erica Hartmann, was inspired to conduct the research after hearing concerns that flushing the toilet could generate a cloud of aerosol particles. She and her team affectionately called their study “Operation Pottymouth”.

I’m not saying you can’t put toilet spray on your toothbrush when you flush. But, from what we saw in our study, the overwhelming majority of germs on your toothbrush are likely coming from your mouth. “

Erica Hartmann, Sstudy Senior Author, Northwestern University

The study will be published on February 1 in the journal Microbiome.

Hartmann is an assistant professor of environmental engineering at the McCormick School of Engineering at Northwestern. Ryan Blaustein, a former postdoctoral fellow in Hartmann’s lab, was the first author of the article. Blaustein is now a postdoctoral fellow at the National Institutes of Health (NIH).

Collecting samples

To get toothbrushes for the study, Hartmann’s team started the Toothbrush Microbiome Project, which asked people to mail in their used toothbrushes with the corresponding metadata. Hartmann’s team then extracted DNA from the hairs to examine the microbial communities within. They compared these communities to those described by the Human Microbiome Project, an NIH initiative that identified and cataloged microbial flora from different areas of the human body.

“A lot of people have provided samples to the Human Microbiome Project, so we have a general idea of ​​what the human microbiome looks like,” Blaustein said. “We have found that the microbes in toothbrushes have a lot in common with the mouth and skin and very little in common with the human gut.”

“Your mouth and gut are not separate islands,” Hartmann added. “There are microbes that we find in both the human gut and mouth, and these microbes are found on toothbrushes. But, again, they’re probably coming from your mouth.

Clean mouth, clean toothbrush

During the research, Hartmann’s team looked at how many different types of microbes lived on toothbrushes. They found people with better oral hygiene, who regularly flossed 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 that’s a small difference. It’s not like the people who regularly floss, brush their teeth and use a mouthwash don’t have germs and those who don’t have loads of them.

The researchers also found that microbes in toothbrushes of people with better oral hygiene had slightly more antimicrobial resistance genes. Hartmann said the microbes with these genes did not match the human body and were probably air or dust in the bathroom.

Hartmann emphasizes that there is no need to be alarmed by germs living on your toothbrush. Unless your dentist recommends otherwise, people should not take antimicrobial toothpaste and toothbrushes.

“By using antimicrobials, you don’t just get rid of germs,” Hartmann said. “You are pushing the surviving microbes towards antimicrobial resistance. In general, for most people, regular toothpaste is sufficient.”