Kytococcal and Staphylococcal strains isolated from Japanese subjects with foot malodor and their control

AIMS: Human foot malodor has been reported to be derived from volatile fatty acids, mainly isovaleric acid, generated by foot bacteria, especially staphylococcal species. However, the knowledge of foot odor is limited compared with axillary odor. Therefore, this study was conducted to identify the causative bacteria of foot malodor in Japanese individuals and to explore methods for controlling foot odor. METHODS AND RESULTS: 16S rRNA gene-targeted microbiome analysis and qPCR analysis were performed on samples from the plantar surface and toe clefts. 16S rRNA gene sequencing was used to identify isolates. Commercially available botanical extracts were screened for their ability to inhibit microbial production of malodorous compounds, specifically the conversion of L-leucine to isovaleric acid. Microbiome analysis and qPCR indicated that Kytococcus is associated with the intensity of isovaleric acid-like odor. 16S rRNA gene analysis of isolates identified Kytococcus schroeteri and Staphylococcus hominis as isovaleric acid-producing strains. Screening of botanical extracts revealed that Sanguisorba officinalis and Eucalyptus globulus extracts effectively inhibited the generation of isovaleric acid from L-leucine. CONCLUSIONS: Kytococcus, particularly K. schroeteri and S. hominis are implicated in isovaleric acid-mediated foot malodor in Japanese subjects. Extracts of Sanguisorba officinalis and Eucalyptus globulus show potential as control agents by inhibiting microbial production of isovaleric acid.