Microbial Trends in Acne and Rosacea

TEM of Cutibacterium acnes
TEM of propionibacterium acnes
The microbial diversity and relative abundance of bacterial taxa in acne patients and rosacea patients reveal species significantly enriched in rosacea and not acne.

The differentially abundant taxa observed in the skin microbiota of patients with acne and patients with rosacea was detailed in study data published in Experimental Dermatology. Cutibacterium acnes (C. acnes) and Serratia marcescens were significantly enriched in rosacea compared with acne, although the relative abundance of C. acnes was similar across patients with acne and patients with rosacea who presented with inflammatory papules and pustules.

Investigators conducted a cross-sectional, case-control study of the skin microbiota in patients with acne, patients with rosacea, and control participants. Patients were matched to control participants by race, sex, and 5-year age intervals. Eligible participants were ≥18 years of age and had not recently undergone any medical treatment with antibiotics, steroids, or anti-inflammatory drugs. Patients were asked to abstain from facial washing and cosmetics prior to sampling. Swabs were taken from the skin of the bilateral cheeks and nose of each participant. Metagenomic DNA was extracted from swabs; polymerase chain reaction (PCR) amplification was performed on the V3V4 hypervariable region of the 16S ribosomal RNA (rRNA) gene. Genes were sequenced using the Illumina MiSeq 300-base pair paired-reads platform. The resulting 16S sequences were assigned to operational taxonomic units (OTUs) based on bacteria sequence similarities. OTU composition was compared across patients at each phylogenetic level. Alpha- and beta-diversity—representing intra- and inter- sample diversity, respectively—were calculated for each patient group.

Samples were collected from 54 participants: 8 patients with acne, 8 acne control participant, 19 patients with rosacea, and 19 rosacea control participants. Mean alpha (intra-sample) diversity was significantly higher in samples taken from patients with acne (5.064 ± 0.772) vs patients with rosacea (3.908 ± 0.991) (P =.006). However, mean alpha diversity also varied significantly in control participants for acne (5.040 ± 0.803) and control participants for rosacea (3.773 ± 1.051) (P =.006), suggesting that demographic characteristics may have contributed to observed microbial differences in  acne and rosacea. Regarding beta (inter-sample) diversity, community composition was significantly different across all 4 participant groups: patients with acne; control participants for acne; patients with rosacea; and control participants for rosacea (P =.004). Proteobacteria was the most abundant phylum in patients with acne (50.260% ± 23.444%) and acne control participants (50.865% ± 15.679%), and Actinobacteria was most abundant for patients with rosacea (38.149% ± 20.784%) and rosacea control participants (43.724% ±23.717). The most abundant species across all patient groups was C. acnes, a member of the Actinobacteria phylum. Notably, the relative abundance of C. acnes in patients with rosacea with inflammatory papules and pustules (20.454% ±16.943%) was more similar to that of patients with acne (19.055% ±15.469%) than that of patients with other types of rosacea (30.419% ±21.862%) (P =.048). Serratia marcescens was significantly enriched in rosacea compared with acne (P =.038).

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As study limitations, investigators noted that between-patient differences also persisted across control groups, suggesting that demographic characteristics may have significantly impacted findings. Further, the small study cohort may limit generalizability.

These findings elucidate certain microbial elements in patients with acne and patients with rosacea.  Describing the microbial diversity and abundance of taxa in rosacea and acne is essential to understanding the pathophysiology of each condition, investigators wrote.

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Thompson KG, Rainer BM, Antonescu C, et al. Comparison of the skin microbiota in acne and rosacea [published online April 11, 2020]. Exp Dermatol. doi: 10.1111/exd.14098