Skin Microbiome

Original Editor - Oyemi Sillo

Top Contributors - Oyemi Sillo and Aminat Abolade  

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Introduction

The skin is the largest organ of the human body and it serves as a physical barrier that protects the body from invasion by foreign organisms. The skin is colonized by millions of microorganisms, which make up the skin microbiome. These include bacteria, fungi, viruses, and mites. As with the gut, the microbiome of the skin plays a role in immunity, healing and health.

Composition of the Skin Microbiome

The composition of the skin microbiome varies among individuals and between body parts, and it is influenced by several factors.

Aside from host factors, interactions between microorganisms also influence the composition and function of the skin microbiome. Microbial interactions can be competitive, where the presence of one diminishes the presence of another, or synergistic, where their presence is mutually beneficial. For instance, Staphylococcus aureus colonizes the nostrils of about a third of the population and is harmless most of the time, however, it is a major risk factor for serious infection. Certain strains of Staphylococcus epidermidis have been reported to inhibit S. aureus.

Role of Skin Microbiome on Immunity

The skin microbiome helps to prime the cells of the immune system for response to attacks by pathogens. Commensal microorganisms interact closely with the host immune cells, training T cells to respond to potential pathogen. Current evidence has shown that rather than a single pathogen causing a disease, disease states are the results of microbial dysbiosis, which lead to aberrant immune responses both locally and systemically. Staphylococcus epidermidis colonizes the skin during the neonatal period, possibly establishing immune tolerance by the accumulation of commensal-specific regulatory T cells following another exposure later in life. Atopic Dermatitis is an immune-mediated inflammatory disease of the skin, in which commensal bacteria of the Staphylococcus species - particularly Staphylococcus aureus - are implicated.

Role of Skin Microbiome on Wound Healing

The skin microbiome has been found to play a role in the healing of chronic wounds in people with diabetes. People with poorly controlled glucose levels have relatively greater abundance of Staphylococcus spp. and Streptococcus spp. Colonization. Also, studies have shown that more than half of diabetic foot ulcers are infected, with associations between the clinical features and the colonizing bacterial communities. For instance, Staphylococcus spp., particularly S. aureus, are associated with shallow ulcers and ulcers of short duration; whereas, ulcers that are deep or of long duration tend to have more diverse mirobial community, with the presence of anaerobic bacteria and Gram-negative Proteobacteria spp.

Physiological stressors, like metabolic disease, and psychological stressors, such as depression, can modify microbial physiology in a way that increases their virulence, causing nonpathogenic microbes to transit to a pathogenic state. This impairs the body’s wound healing responses, and promotes infections.