Whether we like or not, the surface of our skin is a breeding ground for fungi, bacteria, and viruses, even though little is known about the purpose they serve. Considered the first study of its kind, research by scientists from the National Institutes of Health analyzed the DNA make up of fungi found on different areas of the body.

"The data from our study gives us a baseline about normal individuals that we never had before," explained senior co-author Dr. Julie Segre, Ph.D. "The bottom line is your feet are teeming with fungal diversity, so wear your flip flops in locker rooms if you don't want to mix your foot fungi with someone else's fungi."

Using human genome sequencing, Segre and her colleagues analyzed 14 fungus samples from different body locations taken from 10 healthy adults. DNA sequencing of fungi identified five million markers that represent over 80 various types of fungi.

"DNA sequence-based methods of identification enabled us to differentiate among species of fungi and to conclude that the diversity of fungi is highly dependent on the body site rather than the person who is sampled. Our study focused on areas of the skin where we commonly find skin diseases that have been associated with fungi," said Dr. Heidi Kong, M.D., co-senior author and an investigator in the dermatology branch of NCI's Center for Cancer Research.

Their findings showed that 20 percent of the people enrolled in the study were suffering from some kind of fungal infection, including athlete's foot, heel and toe webbing, and toenail deformities. Areas of the foot with the highest concentration of fungi included the heel where 80 genus types were found, the toenail with 60 genus types, and the web of the toes with 40 genus types.

"DNA sequencing reveals the great diversity of fungi, even those that are hard to grow in culture," said Segre, an expert in the development of microbial DNA sequencing technology. "DNA sequencing enabled us to learn immeasurably more about where fungi predominate as a part of the human skin microbiome."

The research team emphasized the importance of their findings in terms of treatment and prevention. Although fungus on human skin appears to remain stable over time, it is still considered one of the top contributors to bloodstream infection.

"Fungal communities occupy complex niches, even on the human body," said Kong. "By gaining a more complete awareness of the fungal and bacterial ecosystems, we can better address associated skin diseases, including skin conditions which can be related to cancer treatments."

The results of the study were published in the May 22 edition of the online journal Nature.

Source: Segre J, Kong H. NIH researchers conduct first genomic survey of human skin fungal diversity. Nature. 2013