The Role of the Skin Microbiome in Atopic Dermatitis: A Systematic Review

Summary

Background

Dysbiosis is a hallmark of atopic dermatitis. The composition of skin microbiome communities and the causality of dysbiosis in eczema have not been well established.

Objective

To describe the skin microbiome profile in atopic dermatitis and address if there is a causal relationship between dysbiosis and atopic dermatitis.

Methods

The protocol is registered in PROSPERO (CRD42016035813). We searched PubMed, Embase, Scopus and ClinicalTrials. gov for primary research studies applying culture-independent analysis on the microbiome on atopic dermatitis skin of humans and animal models. Two authors independently full-text screened studies for eligibility and assessed risk of bias. Because of heterogeneity no quantitative synthesis is made.

Findings

Of 5735 texts, 32 met the inclusion criteria and 17 of these are published; 11 human and 6 animal studies. The studies varied in quality and applied different methodology. The skin in atopic dermatitis had low bacterial diversity (lowest at dermatitis involved sites) and 3 studies showed depletion of Malassezia species and high non-Malassezia fungal diversity. The relative abundance of Staphylococcus aureus and Staphylococcus epidermidis were elevated and other genera were reduced, incl. Propionibacterium. A mouse study indicated that dysbiosis is a driving factor in eczema pathogenesis.

Conclusion

The data is not sufficiently robust for good characterisation; however, dysbiosis in atopic dermatitis does not only implicate Staphylococcus species, but also microbes such as Propionibacterium and Malassezia. A causal role of dysbiosis in eczema in mice encourages future studies to investigate if this applies in humans too. Other important aspects are temporal dynamics and the influence of methodology on microbiome data.

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