Abstract
BackgroundEven though human sweat is odorless, bacterial growth and decomposition of specific odor precursors in it is believed to give rise to body odor in humans. While mechanisms of odor generation have been widely studied in adults, little is known for teenagers and pre-pubescent children who have distinct sweat composition from immature apocrine and sebaceous glands, but are arguably more susceptible to the social and psychological impact of malodor.ResultsWe integrated information from whole microbiome analysis of multiple skin sites (underarm, neck, and head) and multiple time points (1 h and 8 h after bath), analyzing 180 samples in total to perform the largest metagenome-wide association study to date on malodor. Significant positive correlations were observed between odor intensity and the relative abundance of Staphylococcus hominis, Staphylococcus epidermidis, and Cutibacterium avidum, as well as negative correlation with Acinetobacter schindleri and Cutibacterium species. Metabolic pathway analysis highlighted the association of isovaleric and acetic acid production (sour odor) from enriched S. epidermidis (teen underarm) and S. hominis (child neck) enzymes and sulfur production from Staphylococcus species (teen underarm) with odor intensity, in good agreement with observed odor characteristics in pre-pubescent children and teenagers. Experiments with cultures on human and artificial sweat confirmed the ability of S. hominis and S. epidermidis to independently produce malodor with distinct odor characteristics.ConclusionsThese results showcase the power of skin metagenomics to study host-microbial co-metabolic interactions, identifying distinct pathways for odor generation from sweat in pre-pubescent children and teenagers and highlighting key enzymatic targets for intervention.
Highlights
Body odor in the animal kingdom frequently plays an important role in defense against predators and survival [1,2,3]
Body odor in humans is believed to be primarily mediated by bacterial decomposition of naturally secreted, non-odorous constituents of sweat, especially fatty acids, branched-chain aliphatic amino acids, glycerol, and lactic acid originating from eccrine, apocrine, and sebaceous glands [5,6,7,8]
While the underarm has been the primary site of investigations for malodor, consumer studies suggested that malodor from the neck and head areas were regions of concern for families and were included in this study (Additional file 1: Table S1)
Summary
Body odor in the animal kingdom frequently plays an important role in defense against predators and survival [1,2,3]. Olfactory cues are believed to have a role in kinship detection and mate selection [4]. Despite these functions, body odor generally has a strong social stigma attached to it, with its social and psychological impact on affected subjects not being fully understood. Body odor in humans is believed to be primarily mediated by bacterial decomposition of naturally secreted, non-odorous constituents of sweat, especially fatty acids, branched-chain aliphatic amino acids, glycerol, and lactic acid originating from eccrine, apocrine, and sebaceous glands [5,6,7,8]. While mechanisms of odor generation have been widely studied in adults, little is known for teenagers and pre-pubescent children who have distinct sweat composition from immature apocrine and sebaceous glands, but are arguably more susceptible to the social and psychological impact of malodor
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