The human scalp surface is an elaborate host to a myriad of microorganisms, which contribute to human health and disease. Dandruff is an unpleasant scalp related condition, which affects a large part of the adult population, worldwide. Several studies have reported the scalp microbiome associated with dandruff and non-dandruff condition in different populations. However, the scalp microbiome of the Indian population is almost unknown yet, at the exception of one study using a culture based method and focusing on Malassezia species (Clavaud C, 2013; Wang L, 2015; Park HK, 2012; Soares RC, 2016 ;Rudramurthy SM, 2014). With the aim to explore the scalp microbiome of an Indian cohort of 140 subjects, including 70 with non-dandruff scalps and 70 with dandruff, a metagenomic approach complete by clinical evaluation and instrumental methods were used. The study has revealed not only the microbial diversity associated with the scalp condition, but also the functional repertoire of these microbes, which may be responsible for causing this condition. High-throughput amplicon (bacterial 16S rRNA V3 region and fungal ITS-1 region) and shotgun metagenome sequencing, and its computational analysis revealed a higher diversity of fungal species in dandruff scalps than in non-dandruff ones. Malassezia restricta and Malassezia globosa were found to be the most abundant fungal species with a relatively higher abundance of Malassezia globosa in non-dandruff scalps as compared to those with dandruff. Among bacterial species, Staphylococcus epidermidis and Propionibacterium acnes were found the most abundant, with Staphylococcus epidermidis being significantly more abundant in the dandruff scalps. Further, a high abundance of unknown and uncultured species of Malassezia was also observed in dandruff scalps, suggesting the presence of other Malassezia species colonizing dandruff scalps, specific to the Indian population. These species might contribute to the patho-physiology of dandruff. The microbial community also showed significant correlations with clinical parameters associated with the host tissue, such as dandruff severity, sebum and hydration levels, transepidermal water loss. Taken together, the results of this study have provided significant insights into the scalp microbiome associated with the Indian population. This paves the way for the development of new approaches to eradicate scaling in dandruff and to maintain a balanced scalp condition.

THE MICROBIAL AND FUNCTIONAL DIVERSITY OF THE MICROFLORA PRESENT ON THE SCALPS OF INDIAN SUBJECTS WITH AND WITHOUT DANDRUFF