Antimicrobial resistance in commensal skin bacteria among individuals without prior exposure to acne therapy

• Although macrolide-resistant S. epidermidis and C. acnes were still isolated from healthy volunteers without a history of antibiotic treatment for acne, resistance rates of skin bacteria were significantly lower in these volunteers than in acne patients. • Compared with acne patient isolates, volunteer isolates showed fewer clade F and more clade K strains, indicating distinct clade distributions of C. acnes between the groups. • The proportion of Clade F among C. acnes isolates increased from 2014 to 2019. Antimicrobial resistance (AMR) in skin bacteria is a salient issue in patients with acne vulgaris. This study aimed to investigate the antimicrobial resistance status of skin bacteria isolated from university student volunteers with no history of treating acne. We evaluated the antimicrobial susceptibility of Staphylococcus epidermidis and Cutibacterium acnes , isolated in 2014 and 2019 from volunteers, and identified macrolide–clindamycin-resistance determinants. C. acnes genotyping was performed by using single-locus sequence typing (SLST). These isolates were compared with isolates obtained from patients with acne. In total, 92 S. epidermidis and 150 C. acnes isolates from 119 volunteers were analyzed. In 2019, the resistance rate of roxithromycin and clindamycin were 27.3% and 25.0% in S. epidermidis , 4.1% and 2.0% in C. acnes , respectively, significantly lower than the rates isolated from patients with acne (P