Skin health: Friendly bacteria keep harmful Staph in check


Scientists have discovered that in healthy skin, harmful Staphylococcus aureus is kept in check by its friendlier cousins, whose numbers are depleted in people with atopic dermatitis, the most common type of eczema.
The researchers found the bacteria on the skin of people with atopic dermatitis were not doing the same thing as the bacteria on the skin of healthy people.
In a paper published in Science Translational Medicine, a team from the University of California-San Diego (UCSD) and colleagues describe how they isolated and grew commensal or “friendly” bacteria that secrete antimicrobial peptides and transplanted them to treat patients with atopic dermatitis. Humans are alive with trillions of microorganisms that live in and on the body and outnumber human cells tenfold.
Scientists are increasingly coming across examples of how these microbial cells and their genetic material – known as the microbiome – can promote or disrupt human health via their intimate relationship with the immune system. The researchers behind the new study screened 10,000 colonies of commensal bacteria found on human skin to determine how many had antimicrobial properties. They also investigated how common they were on healthy and non-healthy human skin.
First author Dr. Teruaki Nakatsuji, a project scientist in the department of dermatology at UCSD School of Medicine, explains what they found:
“We discovered antimicrobial peptides produced by bacteria commonly found on healthy human skin. These novel antimicrobials have selective activity against pathogenic bacteria, but do not harm other commensal bacteria that have a beneficial effect to us.” According to the National Eczema Association, 32 million people in the United States have eczema, including 18 million with moderate to severe eczema or atopic dermatitis – which normally appears as a rash on arms, legs, and cheeks.
Previous research had shown that the disease-causing bacterium Staphylococcus aureus aggravates skin conditions like atopic dermatitis. Human skin provides around 19 square feet of diverse habitats for numerous species of bacteria, fungi, and viruses.
Fetal skin is sterile, but it is soon colonized after birth. The gut is also home to over 1,000 known bacterial species. S. aureus is a common cause of Staph infections. It can develop into the antibiotic-resistant form known as methicillin-resistant S. aureus, or MRSA – a leading cause of death resulting from infection in the U.S.

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