Continuous clinical improvement of mild-to-moderate seborrheic dermatitis and rebalancing of the scalp microbiome using a selenium disulfide-based shampoo after an initial treatment with ketoconazole

Abstract

Objective: Scalp seborrheic dermatitis (SD) is a chronic, relapsing, and inflammatory scalp disease. Studies indicate a global bacterial and fungal microbiota shift of scalp SD, as compared to healthy scalp. Ketoconazole and selenium disulfide (SeS₂ ) improve clinical signs and symptoms in both scalp dandruff and SD.

Aim: The main objective of this study was to investigate the changes in the scalp microbiota diversity and counts in subjects with scalp SD during a two-phase treatment period.

Material and methods: The scalp microbiota and clinical efficacy were investigated in 68 subjects with mild-to-moderate scalp SD after an initial one-month treatment with 2% ketoconazole, and after a 2-month maintenance phase, either with a 1% SeS₂ -based shampoo or its vehicle.

Results: Thirty one subjects in the active and 37 subjects in the vehicle group participated. Ketoconazole provided an improvement of clinical symptoms (adherent (-1.75 p < 0.05), non-adherent (-1.5, p < 0.05)) flakes and erythema (scores 1.67-0.93, p < 0.001), in an increased fungal diversity and in a significant (p < 0.005) decrease of Malassezia spp. SeS₂ provided an additional clinical improvement (-0.8; p = 0.0002 and -0.7; p = 0.0081 for adherent and non-adherent flakes, respectively, at Day 84) compared to the vehicle associated with a low Malassezia spp. count and an additional significant (p < 0.001) decrease of the Staphylococcus spp. level.

Conclusion: Selenium disulfide provides an additional benefit on the scalp microbiota and in clinical symptoms of SD and dandruff after treatment with ketoconazole. The results confirm the role of Staphylococcus spp. in scalp SD and open possible perspectives for preventing relapses.

Keywords: ketoconazole; scalp microbiota; seborrheic dermatitis; selenium disulfide.

FIGURE 1

Changes in the scores of adherent and non‐adherent flakes from D0 to D84, during the two phases of the study. Scores, established on 8 different scalp regions, are expressed as mean ± SD). (Phase 1, ketoconazole treatment: Large dot line; Phase 2, vehicle treatment: small dot line and active treatment: full line)

FIGURE 2

The top 20 most represented bacterial (A) and fungal (B) genera over time for the active and the vehicle group

FIGURE 3

Alpha diversity: variations of the Shannon index for bacterial (A) and fungal (B) microbiota over time, for the active and vehicle group (*: significant p‐value adjusted)

FIGURE 4

Beta diversity for Unifrac distances. The variation of the Unifrac distances (describing the variation of the beta diversity for the bacterial species) is presented as PCoA (A,C), along with the comparison table between time points and groups using ANOSIM analysis (B,D). Two sets of indexes were investigated: the weighted and unweighted unifrac distances which give information focused on the relative abundance and species presence/absence respectively. BH: Benjamini‐Hochberg procedure was used for multiple comparisons adjustment

FIGURE 5

Beta diversity using the Bray‐Curtis index. The variation of the Bray‐Curtis index (describing the variation of the beta diversity for the fungal species) is presented as PCoA (A,C), along with the comparison table between time points and groups using ANOSIM analysis (B,D). Two sets of indexes were investigated: Bray‐Curtis weighted and Bray‐Curtis unweighted indexes which give information focused on the relative abundance and species presence/absence respectively. BH: Benjamini‐Hochberg procedure was used for multiple comparisons adjustment

FIGURE 6

Quantitative changes in Malassezia; Cutibacterium and Staphylococcus counts (log10(cells /cm²) during initial treatment with ketoconazole and during maintenance with either active or vehicle shampoo and changes in the ratios between microbial species Malassezia/Cutibacterium and Cutibacterium/Staphylococcus