The Skin Microbiome: A New Actor in Inflammatory Acne

Our understanding of the role ofCutibacterium acnesin the pathophysiology of acne has recently undergone a paradigm shift: rather thanC. acneshyperproliferation, it is the loss of balance between the differentC. acnesphylotypes, together with a dysbiosis of the skin microbiome, which results in acne development. The loss of diversity ofC. acnesphylotypes acts as a trigger for innate immune system activation, leading to cutaneous inflammation. A predominance ofC. acnesphylotype IA(1)has been observed, with a more virulent profile in acne than in normal skin. Other bacteria, mainlyStaphylococcus epidermis, are also implicated in acne.S. epidermidisandC. acnesinteract and are critical for the regulation of skin homeostasis. Recent studies also showed that the gut microbiome is involved in acne, through interactions with the skin microbiome. As commonly used topical and systemic antibiotics induce cutaneous dysbiosis, our new understanding of acne pathophysiology has prompted a change in direction for acne treatment. In the future, the development of individualized acne therapies will allow targeting of the pathogenic strains, leaving the commensal strains intact. Such alternative treatments, involving modifications of the microbiome, will form the next generation of 'ecobiological' anti-inflammatory treatments.