Microbial exposure and antibiotic resistance gene dynamics shift between indoor and outdoor school activities

School curricular and extracurricular activities, including indoor study and sports like basketball, significantly impact adolescent physical and mental health. However, their effects on hand and nasal microbiomes, particularly regarding antibiotic resistance genes (ARGs), are underexplored. Here, we recruited 42 junior middle school students in Shanghai to investigate microbial composition and ARGs, collecting 336 hand and nasal samples after handwashing, indoor study, indoor basketball, and outdoor basketball. Our results showed that playing basketball either indoors or outdoors increased microbial diversity in nasal cavities and on hands, compared to post-handwashing. Notably, nasal microbiomes were predominantly derived from hand microbiomes, regardless of the activity performed. Among ARGs, macB genes were more abundant after outdoor basketball than indoor basketball, with this difference more pronounced in nasal cavities than on hands. Metagenomic sequencing identified Aureimonas phyllosphaerae as the primary macB gene host. Although this bacterium harbors ARGs, it is non-pathogenic and lacks mobile genetic elements, indicating a low potential for horizontal gene transfer or interspecies ARG transmission. Collectively, even though students may be exposed to more ARGs during outdoor activities, the health risks are likely minimal because the observed ARG bacteria are non-pathogenic and the likelihood of interspecies ARG transmission is low.