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.