Evidence for wastewaters as environments where mobile antibiotic resistance genes emerge

Wastewaters have a high abundance of the bacterial species from which many mobile resistance genes emerged, as well as the genetic elements that provided mobility. This makes wastewaters plausible evolutionary arenas for such mobilization events. The emergence and spread of mobile antibiotic resistance genes (ARGs) in pathogens have become a serious threat to global health. Still little is known about where ARGs gain mobility in the first place. Here, we aimed to collect evidence indicating where such initial mobilization events of clinically relevant ARGs may have occurred. We found that the majority of previously identified origin species did not carry the mobilizing elements that likely enabled intracellular mobility of the ARGs, suggesting a necessary interplay between different bacteria. Analyses of a broad range of metagenomes revealed that wastewaters and wastewater-impacted environments had by far the highest abundance of both origin species and corresponding mobilizing elements. Most origin species were only occasionally detected in other environments. Co-occurrence of origin species and corresponding mobilizing elements were rare in human microbiota. Our results identify wastewaters and wastewater-impacted environments as plausible arenas for the initial mobilization of resistance genes.

Automated summary

Wastewaters are likely environments for the initial mobilization of resistance genes, as they contain abundant bacterial species that serve as sources for many mobile resistance genes and corresponding genetic elements for mobility. Our analysis shows that wastewaters and wastewater-impacted environments have the highest abundance of origin species and mobilizing elements for resistance genes, compared to other environments such as human microbiota. These findings contribute to our understanding of where clinically relevant antibiotic resistance genes may have gained mobility and highlight the importance of wastewater management in combatting the spread of antibiotic resistance.