This study aimed to investigate the skin microbiome and metabolomics of patients with pitted keratolysis.

Pitted keratolysis is a skin infectious disease which can cause an unpleasant smell that can affect self-confidence and interpersonal relationships. The research problem was initiated through a community outreach program organized by the Department of Dermatology Siriraj Hospital, Thailand. From many years of experiences, our dermatologist teams observed that pitted keratolysis was a common disease among naval cadets who wore enclosed footwear for long hours, and it was more prevalent after a boot camp that spanned over months. This disease is chronic with no efficient standard treatment and limited information on the pathogenesis of the disease. Therefore, we propose to conduct a study on the pathogenesis of pitted keratolysis and malodorous feet through a longitudinal study of foot-skin microbiome and associated volatile metabolomic profiles of foot odor. With the unique population, with similar age range, daily activities, and diet, this study will allow to focus on the association of changes in microbiome in relation to pathogenesis of pitted keratolysis and malodorous feet, with fewer cofounding factors.

The skin microbiome is a group of various microorganisms, such as bacteria, fungi, and viruses, residing on skin. Human skin microbiome can differ with respect to age, ethnicity, diet, climate and environment. Recently, there have been numerous studies highlighting the association of microbes with pathogenesis of various skin diseases, such as atopic dermatitis, acne vulgaris, and psoriasis (references?). In this project, we hypothesize that the alteration of skin microbiome as well as changes in metabolite profiles can be associated with the mechanism of the disease. The skin microbiome data generated in this study will be analyzed for microbial profiles using the QIIME2, a next-generation microbiome bioinformatics platform, and a graphic software package, "Statistical Analysis of Taxonomic and Functional Profiles" (STAMP). In parallel, we will apply a high throughput gas chromatography mass-spectrometry-based metabolomics to detect volatile metabolites present in foot odor in association with the observed foot-skin microbiome. This metabolite information will not only provide an additional aspect of pathogenesis of the disease but also might offer a new standard indicator of foot odor that can be further used in clinical practice. Finally, skin microbiome and metabolomic data will be analyzed using various methods of correlation analysis as well as integrative analysis to gain deeper understanding of the disease mechanism at the molecular levels.

The outcomes of this project will provide insights into the pathogenesis of pitted keratolysis. The scientific knowledge gained from the study will be translated into a more effective treatment of the disease. The human microbiome of healthy population and the disease-specific microbiome data will lay the groundwork to develop a human microbiome database for Thai people. Additionally, the success of the project will allow the development of advanced instrumental methodology and an integrative analysis approach to analyze multi -omics data, which will be great assets in advancing multidisciplinary research.

Inclusion Criteria:

• Naval rating cadets at Chumpol Naval Rating School, Thailand who volunteer to participate in this study. Informed consent will be obtained from all participants.
• Age ≥ 18 years.
• No underlying disease.
• Normal BMI (18.5-22.9 kg/m2).
• No previous history of pitted keratolysis.
• No previous history of dermatophytosis complex.
• Refrain from washing their feet for 12 hours prior to sampling.

Exclusion Criteria:

• Volunteers who have taken medication or topical antibiotics for pitted keratolysis within 2 weeks before the enrollment.
• Volunteers who have taken oral antibiotics within 2 weeks before enrollment.