Abstract
The anaerobic bacterium Propionibacterium acnes is believed to play an important role in the pathophysiology of the common skin disease acne vulgaris. Over the last 10 years our understanding of the taxonomic and intraspecies diversity of this bacterium has increased tremendously, and with it the realisation that particular strains are associated with skin health while others appear related to disease. This extensive review will cover our current knowledge regarding the association of P. acnes phylogroups, clonal complexes and sequence types with acne vulgaris based on multilocus sequence typing of isolates, and direct ribotyping of the P. acnes strain population in skin microbiome samples based on 16S rDNA metagenomic data. We will also consider how multi-omic and biochemical studies have facilitated our understanding of P. acnes pathogenicity and interactions with the host, thus providing insights into why certain lineages appear to have a heightened capacity to contribute to acne vulgaris development, while others are positively associated with skin health. We conclude with a discussion of new therapeutic strategies that are currently under investigation for acne vulgaris, including vaccination, and consider the potential of these treatments to also perturb beneficial lineages of P. acnes on the skin.
Highlights
The human skin, which is the largest organ of the body, is composed of a variety of key microbial genera associated with skin health, including Staphylococcus, Propionibacterium, Streptococcus, Corynebacterium and Malassezia [1]
Along with other well described cutaneous propionibacteria (P. avidum, P. granulosum), it is believed to play an important role in maintaining skin health via occupation of ecological niches that could be colonised by more pathogenic microbes; it produces short chain fatty acids, thiopeptides, bacteriocins and other molecules with inhibitory properties against such organisms [2,3,4]
The development of various molecular typing methods for P. acnes, Multilocus Sequence Typing (MLST) protocols validated by whole genome sequencing (WGS), has provided the opportunity to investigate the population genetic structure of the bacterium, and identify specific STs or lineages that may be associated with skin health and disease
Summary
The human skin, which is the largest organ of the body, is composed of a variety of key microbial genera associated with skin health, including Staphylococcus, Propionibacterium, Streptococcus, Corynebacterium and Malassezia [1]. A further example of the changing views on the pathophysiology of acne can be seen with the recent suggestion that little evidence exists for follicular keratinocyte hyperproliferation in acne lesions versus autologous healthy hair follicles, and that alternate mechanisms may exist for infundibular hyperkeratinisation [45]. Such results serve to highlight the complicated and multifactorial nature of the disease process underlying acne and the challenges facing researchers, including fully elucidating the role played by P. acnes
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