Microbes on your toothbrush match microbes inside your mouth
Northwestern University
After studying microbial communities living on bristles from used toothbrushes, Northwestern University researchers found those communities matched microbes commonly found inside the mouth and on skin.
This was true no matter where the toothbrushes
had been stored, including shielded behind a closed medicine cabinet door or
out in the open on the edge of a sink.
The study's
senior author, Erica Hartmann, was inspired to conduct the research after
hearing concerns that flushing a toilet might generate a cloud of aerosol
particles. She and her team affectionately called their study "Operation
Pottymouth."
"I'm not saying that you can't get toilet aerosols on your toothbrush when you flush the toilet," Hartmann said. "But, based on what we saw in our study, the overwhelming majority of microbes on your toothbrush probably came from your mouth."
The study is published in the journal Microbiome.
Hartmann is an
assistant professor of environmental engineering at Northwestern's McCormick
School of Engineering. Ryan Blaustein, a former postdoctoral fellow in
Hartmann's lab, was the paper's first author. Blaustein is now a postdoctoral
fellow at the National Institutes of Health (NIH).
Collecting samples
To obtain toothbrushes for the study, Hartmann's team launched the Toothbrush Microbiome Project, which asked people to mail in their used toothbrushes along with corresponding metadata. Hartmann's team then extracted DNA from the bristles to examine the microbial communities found there.
They compared these communities
to those outlined by the Human Microbiome Project, an NIH initiative that
identified and catalogued microbial flora from different areas of the human body.
"Many
people contributed samples to the Human Microbiome Project, so we have a
general idea of what the human microbiome looks like," Blaustein said.
"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 mouth, and those microbes
are found on toothbrushes. But, again, those are probably coming from your
mouth."
Clean mouth, clean toothbrush
During the
research, Hartmann's team examined how many different types of microbes lived
on the 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, then your toothbrush also will be relatively
clean," Hartmann said. "But it's a small difference. It's not like
people who regularly floss, brush and use mouthwash have no microbes and those
who don't have tons. There's just a bit less diversity on toothbrushes from
people who do all those things."
The researchers
also found that microbes from toothbrushes of people with better oral hygiene
had slightly more antimicrobial-resistance genes. Hartmann said microbes with
these genes did not match the human body and were likely from air or dust in
the bathroom.
Hartmann
stresses that there's no need to be alarmed by microbes living on your
toothbrush. Unless your dentist recommends otherwise, people should not reach
for antimicrobial toothpastes and toothbrushes.
"By using
antimicrobials, you aren't just getting rid of microbes," Hartmann said.
"You are pushing the surviving microbes toward antimicrobial resistance.
In general, for most people, regular toothpaste is sufficient."