The influence of age, gender and race/ethnicity on the composition of the human axillary microbiome

Objective: The microbial community plays an important role in the generation of human axillary odour by transforming odourless natural secretions into volatile odorous molecules. A limited number of traditional culturing methods and molecular based research have been performed to characterize the human axillary microbiome in small collection sample sizes. Moreover, only a few have considered the interpersonal variations across age, gender or race/ethnicity, and none have included all three variables within one single study. The aim of this study was to characterize the axillary microbiome of healthy subjects across different age groups, genders and races/ethnicities in a large sample size. Methods: The underarm skin swab samples were collected from 169 healthy subjects. The axillary microbiome was analysed by IS-pro, a clinically validated high-throughput DNA fingerprinting technique. Results: The results indicate that the senior subjects (55+) tend to have a higher number of total bacterial than younger adults (of a defined age). The diversity of odour causing bacteria, e.g. corynebacteria, increases with age. Among the three races/ethnicities studied, East Asians have a unique microbial composition compared to Caucasians and Hispanics, which may contribute to the different odour profiles observed among the races/ethnicities studied. Conclusion: Human axillary microbiome varies by age, gender and race/ethnicity. This study has provided an unprecedented fundamental knowledge about the axillary microbiota as a function of age, gender and race/ethnicity.