Atopic dermatitis (AD), a chronic inflammatory skin condition and the most common form of eczema, is estimated to afflict as much as 10 percent of the U.S. population, and is much more common now than it was 50 years ago. Veterinary clinical estimates also show that approximately 10 percent of dogs have atopic dermatitis. How AD arises isn’t yet fully understood, but a new study from researchers from the Perelman School of Medicine at the University of Pennsylvania and Penn’s School of Veterinary Medicine, have uncovered important insights about the association of AD in dogs compared to humans. The study appears online in the Journal of Investigative Dermatology.

To a greater extent than mouse models, canine AD shares important features of the human version. For example, in both humans and dogs AD has been linked to abnormal blooms of Staphyloccocusbacteria on the skin – mostly Staphyloccocus aureus in humans, andStaphyloccocus pseudintermedius in dogs.

In the study, the research team, comprised of veterinary dermatologists, microbiologists, pathologists, and primary scientists, tracked the bacterial populations, or “microbiomes,” on dogs’ skin, and key properties of the skin’s barrier function during an occurrence of AD, and again after standard treatment with antibiotics. During the flare, researchers observed a sharp decrease in the diversity of the skin bacterial population as certain bacterial species proliferated, along with a decrease in the skin’s protective barrier. With antibiotic therapy, both measures returned to normal levels.

“In both canine and human atopic dermatitis we hypothesize there is a similar relationship among skin barrier function, the immune system, and microbes, even if the individual microbe species aren’t identical,” said senior author Elizabeth A. Grice, PhD, an assistant professor of Dermatology and Microbiology at the Perelman School of Medicine at the University of Pennsylvania. “The hope is that insights gained from this study and others like it will enable us one day to treat this condition by altering the skin’s microbiome without antibiotics.”

Thirty-two dogs (15 with canine AD, and 17 without) from Penn Vet’s Ryan Hospital were enrolled in the study. On three occasions – first during AD flares in the affected dogs, then after 4-6 weeks of targeted antibiotics, and finally 4-6 weeks after treatment concluded – the team took swabs from several areas of skin on the affected dogs. They surveyed the microbiomes of these samples by amplifying and sequencing copies of a key bacterial gene whose DNA sequence is distinct for different bacterial species.