Modulations of the skin microbiome in skin disorders: A narrative review from a wound care perspective

Abstract

The cutaneous microbiome represents a highly dynamic community of bacteria, fungi and viruses. Scientific evidence, particularly from the last two decades, has revealed that these organisms are far from being inconsequential microscopic hitchhikers on the human body, nor are they all opportunistic pathogens waiting for the chance to penetrate the skin barrier and cause infection. In this review, we will describe how dermatological diseases have been found to be associated with disruptions and imbalances in the skin microbiome and how this new evidence had shaped the diagnosis and clinical practice relating to these disorders. We will identify the microbial agents which have been found to directly exacerbate skin diseases, as well as those which can ameliorate many of the symptoms associated with dermatological disorders. Furthermore, we will discuss the studies which suggest that bacteriotherapy, either by topical use of probiotics or by bacteria-derived compounds, can rectify skin microbial imbalances, thereby offering a promising alternative to antibiotic treatment and reducing the risks of antibiotic resistance.

Keywords: microbiota; multiple drug resistance; probiotics; skin; wounds and injuries.

FIGURE 1

The commensal cutaneous microbiota is involved in many physiological processes in the skin. Left panel: the skin microbiota and its interactions with the host in a healthy state. Sphingolipids in the skin that protect the skin barrier are produced either entirely from metabolic processes within the host, or in response to bacterial‐derived metabolic enzymes. The commensal microbiota also interacts with the host's immune system, which in turn becomes primed to fight future pathogenic invasion and precipitates molecular cascades in keratinocytes which aid in suppressing the overgrowth of opportunistic pathogens on the skin surface. Right panel: the consequences of impaired skin barrier integrity and/or a dysbiotic skin microbiome. A compromised skin barrier can result in either epidermal thickening or thinning, leading to transepidermal water loss (TEWL) which, among other alterations, can change the environment and thus favour the overgrowth of opportunistic pathogens. Furthermore, microbial species can slip through the compromised skin barrier and cause infection within the host, precipitating localized and systemic inflammatory processes.