ARG(H), Another Challenge? Assessing the Risk of the Spaceborne Gut Microbiome as a Reservoir for Antibiotic Resistance

Abstract

Antimicrobial resistance is a critical global health threat, causing over one million annual deaths worldwide. Resistant infections also pose a threat to astronauts during spaceflight, as they experience immune dysregulation, and pathogens become more virulent in outer space. The gut microbiome is a possible source of pathogens and antimicrobial resistance genes (ARGs) during spaceflight, as it serves as the origin for many of the microbes observed in the environment of the International Space Station (ISS). This study used metagenomic sequencing data from the Rodent Research-9 mission to evaluate whether ARG abundance, identity, and presence on plasmids in the gut microbiome increased during spaceflight, and whether microbiome ARGs were exchanged with the spacecraft environment. Five mice flew a 33-day mission to the ISS, and fecal samples were sequenced after their return, along with those from five control groups. Both whole samples and plasmid DNA were searched for ARGs, and those found were compared to ARGs detected in past studies of the ISS environment. ARG abundance and presence on plasmids did not significantly change during spaceflight, and only eleven genes were found in both the flight group microbiomes and the ISS environment, indicating little exchange between the two areas. Very few ARGs detected conferred resistance to the antibiotic classes nitroimidazoles, bicyclomycins, and oxazolidinones, making them effective choices for future missions. Overall, these results indicate that the microbiome likely does not pose a significant source of resistant infection during spaceflight, and additional safety measures may not be necessary.