Skin microbiome and acne vulgaris: Staphylococcus, a new actor in acne.

Propionibacterium acnes (P. acnes), the sebaceous gland and follicular keratinocytes are considered the three actors involved in the development of acne. This exploratory study investigated the characteristics of the skin microbiota in subjects with acne and determined microbiota changes after 28 days of application of erythromycin 4% or a dermocosmetic. Skin microbiota were collected under axenic conditions from comedones, papulo-pustular lesions and non-lesional skin areas from subjects with mild to moderate acne according to the GEA grading using swabs. Samples were characterized using a high-throughput sequencing approach that targets a portion of the bacterial 16S rRNA gene. Overall, microbiota samples from 26 subjects showed an overabundance of Proteobacteria and Firmicutes and an under-representation of Actinobacteria. Staphylococci were more abundant on the surface of comedones, papules and pustules (P=.004 and P=.003 respectively) than on non-lesional skin. Their proportions increased significantly with acne severity (P<.05 between GEA-2 and GEA-3). Propionibacteria represented less than 2% of the bacteria on the skin surface. At Day 28, only the number of Actinobacteria had decreased with erythromycin while the dermocosmetic decreased also the number of Staphylococci. A significant reduction (P<.05) from Day 0 of comedones, papules and pustules with no significant difference between the products was observed. The bacterial diversity on all sampling areas was similar. The dermocosmetic decreased the number of Actinobacteria and Staphylococcus spp. after 28 days. Staphylococcus remained the predominant genus of the superficial skin microbiota. No significant reduction in Staphylococcus spp. was observed with the topical antibiotic.