Staphylococcus capitis may contribute to dandruff pathogenesis by driving abnormal amino acid metabolism and microbial pathogenesis on the scalp, according to a recent study.
Researchers investigated microbial functions in dandruff pathogenesis and scalp health. The study, published in the Journal of Investigative Dermatology, used metagenomic sequencing to analyze scalp microbiota from participants with and without dandruff, focusing on amino acid metabolism and pathogenesis.
The study included 98 participants, 66 with dandruff (Adherent Scalp Flaking Scale [ASFS] ≥10) and 32 controls (ASFS ≤6). Scalp samples were analyzed for microbial composition and function. Participants with dandruff were randomized into two treatment groups: one used a shampoo base with surfactants (n = 31), while the other used a triplex shampoo containing anti-dandruff agents, including piroctone olamine, sorbitan caprylate, and succinic acid (n = 33). Treatments lasted four weeks, with pre- and post-treatment comparisons of microbial diversity and functional profiles.
Zhijue Xu, PhD, and colleagues reported that participants with dandruff had a significantly higher Shannon diversity index (P<0.05) and a distinct microbial structure. Increased Staphylococcus capitis and Malassezia restricta abundance was noted, alongside downregulation of alanine catabolism and upregulation of amino acid biosynthesis and pathogenesis-related pathways. Of 653 altered GO annotations, 584 were upregulated, including "pathogenesis," and 69 were downregulated, such as "amino acid transport."
Six functional annotation clusters linked to dandruff pathogenesis were identified. Cluster 1 involved all microorganisms and was associated with amino acid biosynthesis. Clusters 2, 4, and 5 were predominantly driven by Malassezia, Staphylococcus, and Cutibacterium species, respectively. The study noted that deeper sequencing might be required to determine the specific biological roles of Malassezia restricta.
Both shampoos effectively reduced ASFS scores (base: 17.2 to 12.7, P<0.001; triplex: 23.2 to 14.8, P<0.001) and microbial diversity. The triplex shampoo demonstrated superior efficacy in reducing pathogenesis-related functions and enhancing amino acid transport. These effects were attributed to the anti-dandruff agents, which modified the scalp microenvironment by altering microbial functionality.
The study highlighted the downregulation of alanine catabolism, primarily driven by Cutibacterium acnes, suggesting alanine accumulation and its potential role in promoting microbial proliferation. Upregulated amino acid biosynthesis and increased tRNA ligase activity indicated heightened protein synthesis in dandruff-associated microbiota.
Ethical approval was granted by the Scientific and Ethical Committee at Shanghai Jiao Tong University (approval ID: B20240204I), and all participants provided written informed consent.
The researchers concluded that targeting microbial functionality, particularly through anti-dandruff agents, may be an effective strategy for dandruff management.
The authors declared having no competing interests.
