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Skin microbes fairly stable over time

The health of our skin depends upon the delicate balance between our own cells and the countless microbes that live on its surface.Piotr Marcinski/iStock/Thinkstock

Your skin serves as one of the first lines of defense against illness and injury. Its health depends on the balance between your own cells and the millions of microbes—including bacteria, fungi, and viruses—that live on its surface. But during an average day, parts of your skin may brush surfaces in stores, elevators, and restrooms; get nicked by a kitchen knife; be washed with rain; rest on a gym mat; and be slobbered on by a dog.

Given this wide range of exposures, an NIH research team set out to determine how skin microbial communities change over time. The team was led by Drs. Heidi H. Kong and Julia A. Segre of NIH’s National Cancer Institute (NCI) and National Human Genome Research Institute (NHGRI), respectively. Results were published on May 5, 2016, in Cell.

The researchers collected a total of nearly 600 skin samples from 12 healthy adult volunteers (7 men and 5 women) at 3 time points—5-10 weeks apart (“short”) and 10-30 months apart (“long”). The samples were taken from 17 body regions representing 4 microenvironments. These included oily areas (such as the side of the nose, inside the ear, and upper chest); moist areas (typically skin folds or creases such as the inner elbow, space between fingers, and behind the knee); dry, flat surfaces (such as the inside of the forearm and palm of the hand); and the feet (toenail, heel, and between the toes).

The group used genomic techniques to create a comprehensive inventory of the microbes in the samples. They found that the bacterial, fungal, and viral communities were fairly stable over the time period studied despite the skin’s routine exposure to a wide range of environments during daily life. The nature and extent of the microbial stability varied across the people studied, such that each person had a unique microbial signature.

Some differences were observed among the body areas sampled. Sites with oily skin had more stable bacterial and fungal communities. In contrast, sites from the foot showed the most variability over both the short and long term. The palm, which is a dry site that typically undergoes a wide range of exposures, was remarkably stable over time.

“Future studies can use the knowledge of the relative stability of the skin microbial communities in healthy adults to understand how various exposures or disease state may alter these skin microbes,” Segre says.

“Finding this relative microbial stability in healthy skin is also important for potential studies that explore whether we can change our skin microbes,” Kong adds.

—by Carol Torgan, Ph.D.