Patrick L.J.M. Zeeuwen; Michiel Kleerebezem; Harro M. Timmerman; Joost Schalkwijk

Disclosures

Curr Opin Allergy Clin Immunol. 2013;13(5):514-520. 

In This Article

Abstract and Introduction

Abstract

Purpose of review: This article reviews recent findings on the skin microbiome. It provides an update on the current understanding of the role of microbiota in healthy skin and in inflammatory and allergic skin diseases.

Recent findings: Advances in computing and high-throughput sequencing technology have enabled in-depth analysis of microbiota composition and functionality of human skin. Most data generated to date are related to the skin microbiome of healthy volunteers, but recent studies have also addressed the dynamics of the microbiome in diseased and injured skin. Currently, reports are emerging that evaluate the strategies to manipulate the skin microbiome, intending to modulate diseases and/or their symptoms.

Summary: The microbiome of normal human skin was found to have a high diversity and high interpersonal variation. Microbiota compositions of diseased lesional skin (in atopic dermatitis and psoriasis) showed distinct differences compared with healthy skin. The function of microbial colonization in establishing immune system homeostasis has been reported, whereas host–microbe interactions and genetically determined variation of stratum corneum properties might be linked to skin dysbiosis. Both are relevant for cutaneous disorders with aberrant immune responses and/or disturbed skin barrier function. Modulation of skin microbiota composition to restore host–microbiota homeostasis could be future strategies to treat or prevent disease.

Introduction

Skin is our largest organ and plays an important protective role against infection and penetration of toxic agents, as it is a major interface between the body and its environment. In utero, the skin is sterile, but after birth environmental microbes rapidly start to colonize the stratum corneum eventually developing into a complex microbial ecosystem that is in homeostasis with its host.[1,2] It is estimated that over 100 distinct species making up a total of 1 million microorganisms colonize each square centimetre of our skin.[3] The total microbial community that lives in association with the human body is collectively known as the human microbiota, and the human skin microbiota includes all microbial members found in a particular cutaneous body site habitat.[4] The diversity of human microbiota is determined by various factors such as transmission of nonresident microbes, genetic predisposition, lifestyle, and host demographic and environmental characteristics.[5,6] Until recently, most of our knowledge of bacteria that reside on skin came from conventional culture-based approaches. However, these approaches have significant limitations, which are due to the fact that only a minority of the bacteria are readily culturable in the laboratory. Moreover, many slow growing organisms from a complex microbial community are overcrowded by bacteria that are better adapted to the in-vitro growth conditions applied. Therefore, culture-dependent microbiota analyses lead to underestimation of diversity and artificial skewing of relative abundances of certain bacterial groups. Advances in DNA sequencing technologies have allowed comprehensive examination of microbial communities using culture-independent methods.[7] These new molecular approaches enable analysis of genetic material derived from complete microbial communities harvested from their natural environment. Comprehensive large-scale projects such as the Human Microbiome Project (HMP),[8] the Metagenomics of the Human Intestinal Tract (MetaHIT) consortium,[9] and the project Microbes in Allergy and Autoimmunity Related to the Skin (MAARS),[10] have revealed the extent of variation in the human microbiota, including the microbiota that resides on the skin.

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