Richard Gallo presented on "Host Microbe Interactions in the pathogenesis of atopic dermatitis."
The size of the skin surface area for microbiota interface is 25 square meters when your take into account the hair follicles. Not only the general size of the hair follicle surface area, but there are also nerve fibers and blood vessels in the hair follicle: https://twitter.com/MatthewBowdish/status/1087466779423662082
The immune system exerts pressure for beneficial interactions but driving microbiota towards commensalism and mutualism and away from competition, amensalism and predation/parasitism. Skin produces antimicrobial peptides (AMPs) that are essential for defense of the skin. AMPS in host control of microbial growth: https://twitter.com/MatthewBowdish/status/1087470294636290049
Another way the skin protects is Reactive Adipogenesis, where AMPs produced by fat cells causes expansion of adipose layer in response to local infections with S aureus. Evidently GI surgeons have used this phenom to find areas of colitis for a century. When they open patients up, they look for the area of the bowel wrapped in more fat..
Pathophysiology of Atopic Dermatitis involves deficiency of AMP. Patients with AD have deficiencies in AMP that lead to susceptibility to Staph aureus. S. aureus seems to trigger AD also. They are both interdependent on each other. Moisturizers improve barrier repair which leads to a decrease in IL4, while increasing AMP. Blocking IL4 reduces Staph. aureus colonization and correlates with improved disease.
Atopic dermatitis promotes Staph aureus but does Staph aureus cause Atopic Dermatitis? In a couple of recent studies, it's been shown that S aureus preceded development of atopic dermatitis - JACI 2017 139(1):166 and J Invest Dermatol 2017 137(12):2497.
Topical and systemic antibiotics are not effective in atopic dermatitis. Antibiotics did not kill Staph. aureus. Antibiotics only worked if impetigo was present clinically. Bleach baths don’t seem to be more effective than regular baths. Bacteria do not seem to be changed by adding bleach.
Plausible molecular explanations for causal association between S aureus and atopic dermatitis: https://twitter.com/MatthewBowdish/status/1087473587575873536
How can we treat atopic dermatitis related to Staph. aureus without use of antibiotics which seem to be ineffective?
Applying topical bacteriotherapy in a small trial completely eliminated Staph. aureus - this is an exciting application of skin microbiome. There were no adverse events from topical application of microbiome therapy. Effective anti Staph. aureus agent. Microbiome transcriptome diversity improved with the application. Skin inflammation improved only after 1 week of application.
This is a Twitter summary from the 2019 WSAAI meeting. This summary was compiled from the tweets posted by Matthew Bowdish @MatthewBowdish and Ray Firszt @RayFirszt, who attended the 2019 Western Society of Allergy, Asthma and Immunology (WSAAI) meeting. The tweets were labeled #WSAAI. The text was edited by me.
Atopic dermatitis maintenance (click to enlarge the image).