NEW ORLEANS, Louisiana — As the study of cutaneous dysbiosis and its role in the pathogenesis of dermatoses continues to evolve, how the mounting evidence on this topic translates into clinical practice remains largely unknown.

“There’s still a lot for us to learn,” Adam Friedman, MD, professor and chair of dermatology at George Washington University, Washington, DC, said at the annual meeting of the American Academy of Dermatology. “Multiple factors contribute to the variability in the skin microbiota, including age, sex, environment, immune system, host genotype, lifestyle, and pathobiology. The question becomes, when do these factors or impacts on the microbiota become clinically significant?”

According to Friedman, there are 10 times more bacteria cells than human cells in the human body, “but it’s not a fight to the finish; it’s not us versus them,” he said. “Together, we are a super organism.” There are also more than 500 species of bacteria on human skin excluding viruses and fungi, and each person carries up to 5 pounds of bacteria, which is akin to finding a new organ in the body.

“What’s so unique is that we each have our own bacterial fingerprint,” he said. “Whoever is sitting next to you? Their microbiota makeup is different than yours.”

Beyond genetics and environment, activities that can contribute to alterations in skin flora or skin dysbiosis include topical application of steroids, antibiotics, retinoids, harsh soaps, chemical and physical exfoliants, and resurfacing techniques. “With anything we apply or do to the skin, we are literally changing the home of many microorganisms, for good or bad,” he said.

In the realm of atopic dermatitis (AD), Staphylococcus aureus has been implicated as an offender in the pathophysiology of the disease. “It’s not about one single species of Staphylococcus, though,” said Friedman, who also is director of translational research at George Washington University. “We’re finding out that, depending on the severity of disease, Staph. epidermis may be part of the problem as opposed to it just being about Staph. aureus. Furthermore, and more importantly, these changes in the microbiota, specifically a decrease in microbial diversity, has been shown to precede a disease flare, highlighting the central role of maintaining microbial diversity and by definition, supporting the living barrier in our management of AD.”

With this in mind, researchers in one study used high-throughput sequencing to evaluate the microbial communities associated with affected and unaffected skin of 49 patients with AD before and after emollient treatment. Following 84 days of emollient application, clinical symptoms of AD improved in 72% of the study population and Stenotrophomonas species were significantly more abundant among responders.

Prebiotics, Probiotics

“Our treatments certainly can positively impact the microbiota, as we have seen even recently with some of our new targeted therapies, but we can also directly provide support,” he continued. Prebiotics, which he defined as supplements or foods that contain a nondigestible ingredient that selectively stimulates the growth and/or activity of indigenous bacteria, can be found in many over-the-counter moisturizers.

For example, colloidal oatmeal has been found to support the growth of S. epidermidis and enhance the production of lactic acid. “We really don’t know much about what these induced changes mean from a clinical perspective; that has yet to be elucidated,” Friedman said.

In light of the recent attention to the early application of moisturizers in infants at high risk of developing AD in an effort to prevent or limit AD, “maybe part of this has to do with applying something that’s nurturing an evolving microbiota,” Friedman noted. “It’s something to think about.”

Yet another area of study involves the use of probiotics, which Friedman defined as supplements or foods that contain viable microorganisms that alter the microflora of the host. In a first-of-its-kind trial, researchers evaluated the safety and efficacy of self-administered topical Roseomonas mucosa in 10 adults and 5 children with AD. No adverse events or treatment complications were observed, and the topical R. mucosa was associated with significant decreases in measures of disease severity, topical steroid requirement, and S. aureus burden

In a more recent randomized trial of 11 patients with AD, Richard L. Gallo, MD, PhD, chair of dermatology, University of California, San Diego, and colleagues found that application of a personalized topical cream formulated from coagulase-negative Staphylococcus with antimicrobial activity against S. aureus reduced colonization of S. aureus and improved disease severity.

And in another randomized, controlled trial, Italian researchers enrolled 80 adults with mild to severe AD to receive a placebo or a supplement that was a mixture of lactobacilli for 56 days. They found that adults in the treatment arm showed an improvement in skin smoothness, skin moisturization, self-perception, and a decrease in the SCORing Atopic Dermatitis (SCORAD) index as well as in levels of inflammatory markers associated with AD.

Friedman also discussed postbiotics, nonviable bacterial products or metabolic byproducts from probiotic microorganisms that have biologic activity in the host. In one trial, French researchers enrolled 75 people with AD who ranged in age from 6 to 70 years to receive a cream containing a 5% lysate of the nonpathogenic bacteria Vitreoscilla filiformis, or a vehicle cream for 30 days. They found that compared with the vehicle, V. filiformis lysate significantly decreased SCORAD levels and pruritus; active cream was shown to significantly decrease loss of sleep from day 0 to day 29.

Friedman characterized these novel approaches to AD as “an exciting area, one we need to pay attention to. But what I really want to know is, aside from these purposefully made and marketed products that have pre- and postprobiotics, is there a difference with some of the products we use already? My assumption is that there is, but we need to see that data.”

Friedman disclosed that he is a consultant and/or advisory board member for Medscape/SanovaWorks, Oakstone Institute, L’Oréal, La Roche Posay, Galderma, Aveeno, Ortho Dermatologic, Microcures, Pfizer, Novartis, Lilly, Hoth Therapeutics, Zylo Therapeutics, BMS, Vial, Janssen, Novocure, Dermavant, Regeneron/Sanofi, and Incyte. He has also received grants from Pfizer, the Dermatology Foundation, Lilly, Janssen, Incyte, and Galderma.

This article originally appeared on, part of the Medscape Professional Network.

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