The Role of the Skin Microbiota in Acne Pathophysiology

S. Ramasamy; E. Barnard; T.L. Dawson Jr; H. Li


The British Journal of Dermatology. 2019;181(4):691-699. 

In This Article

The Pilosebaceous Microbiome

As acne is a disease of the pilosebaceous unit, in this review we focus on the microbiome in the lipid-rich follicle environment. Microbes across different kingdoms are found, including bacteria, fungi, viruses and bacteriophage. Based on 16S rDNA and metagenomic sequencing, the most abundant bacteria are Cutibacteria, with a relative abundance of ~90%, followed by Corynebacterium and Staphylococcus (< 5%).[14,15] With respect to fungal components, ITS/18S and metagenomic sequencing show the eukaryotic composition to be predominantly Malassezia.[16] However, owing to numerous factors including sampling and lysis methods,[17] in addition to sequencing and analysis biases,[18] it is difficult to make a quantitative comparison of the relative impact of bacteria, fungi and viruses/phage in the follicular microbiome (Figure 1). These analyses are also complicated by the very nature of microbiome analyses. Microbiome analyses count the number of genomes present in any given sample, counting one genome as one functional unit. Genomes do not interact with the host, however, the biomass associated with each genome does. As microbial cells are highly variable in size, the biomass per genome fluctuates widely (Table 1). When considering the biomass available to interact with the host, the much larger eukaryotic cells have the potential to interact with several thousand times the biomass of their prokaryotic counterparts.

Figure 1.

Histopathology of acne lesion and sampling sites. SC, stratum corneum; E, epidermis; HF, hair follicle; DER, dermis; SG, sebaceous gland; KM, keratinous material; DHF, dilated hair follicle; ALS1-SC, acne lesion site 1 (surface stratum corneum); ALS2-IIF, acne lesion site 2-infra-infundibulum; ALS3, acne lesion site 3; DS-DHF, deep site-dilated hair follicle.