Rhodomyrtus tomentosa Fruit Extract and Skin Microbiota: A Focus on C. acnes Phylotypes in Acne Subjects

Knowing that Rhodomyrtus tomentosa is known to have antibacterial effects, this study investigated the skin microbiota with a focus on Cutibacterium acnes (C. acnes) phylotypes in subjects with acne, and determined microbiota changes after 28 days of treatment with berries Rhodomyrtus tomentosa as an active ingredient (RT). Skin swabs from seventeen acne subjects were collected and the skin microbiome was analyzed using 16S rRNA gene sequencing. A culture-independent next-generation sequencing (NGS)-based SLST (single-locus sequence typing) approach was aimed at evaluating RT extract effects on C. acnes phylotype repartition. Clinical evaluations (lesion counts) were performed at baseline (D0) and after 28 days (D28) of twice-daily application of the RT active ingredient. We determined: (1) the skin microbiota at D0 was dominated by Actinobacteria followed by Firmicutes and Proteobacteria; (2) at the genus level, Cutibacterium was the most abundant genus followed by Staphylococcus and Corynebacterium; (3) C. acnes was the major species in terms of mean abundance, followed by Staphylococcus epidermidis (S. epidermidis) and Staphylococcus hominis (S. hominis); and (4) phylotype IA1 was most represented, with a predominance of SLST type A1, followed by phylotypes II, IB, IA2, IC, and III. After 28 days of RT extract treatment, phylotype repartition were modified with a decrease in abundance (approximately 4%) of phylotype IA1 and an increase in phylotype II and III. Cutibacterium granulosum (C. granulosum) abundance also decreased. Reduction of retentional and inflammatory lesions was also noted only after RT treatment; thus, RT extract acts as a microbiota-regulating agent.