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12:05 pm
Wed May 22, 2013

Research Reveals Yeasty Beasts Living On Our Skin

Originally published on Fri May 24, 2013 10:20 am

Scientists have completed an unusual survey: a census of the fungi that inhabit different places on our skin. It's part of a big scientific push to better understand the microbes that live in and on our bodies.

"This is the first study of our fungi, which are yeast and other molds that live on the human body," says Julie Segre, of the National Human Genome Research Institute, who led the survey.

Trillions of microbes live everywhere in and on our bodies. Most of these viruses, bacteria and other microorganisms are harmless. Many of them are actually helpful. But scientists are just starting to figure out exactly what they are and what they do.

"A lot of medicine has to do with not just our own human cells but really [is] about how humans interact with the bacteria and fungi that live on our bodies," Segre says.

To assess the fungal population, Segre and her colleagues collected samples from 14 different patches of skin on 10 healthy volunteers.

"We did an exploration where we looked at all the different little crevices of your body," she says.

The researchers then sequenced the fungal DNA in those samples and report what they discovered in this week's issue of the journal Nature.

"What we found was that the human body is an even more diverse ecosystem than we had known when we looked only at the bacterial communities," Segre says.

The survey turned up dozens of types of fungi — far more than anyone knew were there. In most parts of the body, fungi from the genus Malassezia dominated. One part of the body had an especially wide array: the feet.

For example, researchers found at least 80 varieties on the heel, at least 60 between the toes and at least 40 on toenails. Elsewhere on the body, they only identified between two and five types of fungi.

The researchers aren't sure why feet are teeming with such a broad fungal assortment. One possibility is that temperature of our feet fluctuates a lot. Segre says there may be another, simpler explanation: "Even those of us who wear shoes a lot still walk around barefoot, either in our homes or in locker rooms. And there's just great exposure to fungi."

Whatever the explanation, the survey could eventually lead to new ways to treat millions of people who suffer from all sorts of skin conditions, such as toenail infections and athlete's foot.

"It really would certainly underlie the idea that you really do need to take very good care of your feet," Segre says. "So, for example, I do wear flip-flops when I walk around a locker room because I know from these studies that I don't actually want to share the fungi with the, you know, 20 other people who are showering after just going swimming."

The researchers were also surprised when they discovered that one volunteer's fungi were still out of whack seven months after she had taken an antifungal drug.

"We want to think there is a resilience of our bacterial communities, of our fungal communities, and that as soon as we stop medicating that they would bounce back into a state of health," Segre says.

But the volunteer's experience provides more evidence that this expectation is far from the case. It suggests that all the antibiotics, antibacterial products and antifungal medications people use these days may be affecting the good microbes that live on our bodies more than we think.

"The scale at which people are being exposed to antimicrobial drugs is really substantial," says infectious disease specialist Martin Blaser, at New York University. "And it would be surprising if there were not consequences from that."

Researchers plan to use this survey to explore a number of questions, including why women tend to get yeast infections when they take antibiotics. And why do some people get dandruff and some babies get diaper rash while others don't.

"There will be many further follow-up studies looking at the disease state on the skin and what kind of perturbations are associated with both the bacteria and the fungi there," says Joseph Heitman of Duke University, whose research focuses on microbial pathogens.

The results may also yield insights into skin cancer, he says. "What if we were to find the microbes on the skin either increase or decrease the risk for skin cancer, for example? That might be very important information to have," Heitman says.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

ROBERT SIEGEL, HOST:

Scientists have completed an usual survey. It's a census, the first of its kind, of the fungi that live on our skin. As NPR's Rob Stein reports, the survey is part of an effort by scientists to better understand the microbes that inhabit the human body.

ROB STEIN, BYLINE: Trillions of microbes can be found pretty much everywhere on our bodies. Bacteria, viruses, most are harmless and many are actually helpful. But Julie Segre, of the National Institutes of Health, says scientists are just starting to figure out exactly what they are and what they do.

JULIA SEGRE: A lot of medicine has to do with not just our own human cells but really about how humans interact with the bacteria and fungi that live on our bodies.

STEIN: Scientists have learned a lot about the bacteria that live in our digestive systems and other places but fungi, like yeast and other molds, have remained a mystery.

SEGRE: So we did an exploration where we looked at all the different little crevices of your body, the sides of your nose, behind your ears.

STEIN: Inside the elbow, on our backs - all together, the researchers sampled 14 spots on 10 healthy adults and used sophisticated genetic technique to see which funguses were living where. In this week's issue of the journal Nature, they report some surprising results.

SEGRE: What we found was that the human body is an even more diverse ecosystem than we had known when we looked only at the bacterial communities.

STEIN: Dozens of different types of fungi are thriving on our bodies, way more than anyone knew, especially in one place.

SEGRE: The feet.

STEIN: The feet were just teeming with fungi.

SEGRE: We found tremendous diversity of fungi on the feet of these healthy volunteers. On the heel, we could find at least 80 different types of fungi. On the toe, at least 60 different types of fungi when most of the body sites only had between two and five different types of fungi.

STEIN: Scientists aren't sure why that is. It could be something about how our feet go hot and cold so much or it could be something much simpler.

SEGRE: Even those of us who wear shoes a lot still walk around barefoot, either in our homes or in locker rooms. And there's just great exposure to fungi.

STEIN: Whatever the explanation, the survey could lead to new ways to treat millions of people who suffer from all sorts of conditions, conditions caused when fungi run amuck, like toenail infections and athlete's foot.

SEGRE: It really would certainly underlie the idea that you really do need to take very good care of your feet. So, for example, I do wear flip-flops when I walk around a locker room because I know from these studies that I don't actually want to share the fungi with the, you know, 20 other people who are showering after just going swimming.

STEIN: The researchers had another surprise. In one volunteer who had taken an antifungal drug, the normal healthy fungi were still out of whack seven months later.

SEGRE: Oh, that was very surprising to us. We tend to think that there is this resilience of our bacterial communities, of our fungal communities, and that as soon as we stop medicating that they would bounce back into a state of health.

STEIN: But this says maybe not and that all the antibiotics, antibacterial products and antifungals that we use these days may be disrupting the good microbes in and on our bodies more than we think. Martin Blaser's a microbiologist at New York University.

MARTIN BLASER: The scale at which people are being exposed to antimicrobial drugs is really substantial. And it would be surprising if there were no consequences from that.

STEIN: The new survey could help shed light on those consequences and other questions, like why women get yeast infections when they take antibiotics, why some people get dandruff and some babies get diaper rash and others don't, and even perhaps how to prevent skin cancer. Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.

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