Skin Microbiota in Non-inflammatory and Inflammatory Lesions of Acne Vulgaris: The Underlying Changes within the Pilosebaceous Unit

Acne vulgaris is a common chronic inflammatory skin disease of the pilosebaceous unit. Clinical manifestations include seborrhea, non-inflammatory lesions, inflammatory lesions, or scar formation. Fourteen eligible participants of either sex, aged 18-28 years old, with mild to moderate acne lesions, were recruited in this observational study. The contents of 10 pilosebaceous units of non-inflammatory (comedones) and inflammatory lesions (papules and pustules) were collected from each participant's face and examined by amplicon metagenomics sequencing and real-time Polymerase Chain Reaction (PCR). Male participants, participants with a higher body mass index (BMI) than normal, and participants younger than 20 years old, were revealed to have a higher proportion of Malassezia in their non-inflammatory lesions than that in inflammatory lesions. There was an increased abundance of Malassezia restricta (M. restricta) and Cutibacterium acnes (C. acnes) in the non-inflammatory group. Correlation analysis indicated that Staphylococcus epidermidis (S. epidermidis) and M. restricta have similar proliferation trends with C. acnes during the transformation from non-inflammatory to inflammatory lesions. M. restricta probably involve in the microecological balance within the pilosebaceous unit.