Geographics and bacterial networks differently shape the acquired and latent global sewage resistomes

The authors analysed 1,240 untreated urban‐sewage samples from 351 cities in 111 countries (2016-2021) to compare two classes of antimicrobial‐resistance genes (ARGs): “acquired” ARGs (those known to have been mobilised between bacteria) and “functionally‐identified/latent” ARGs (FG ARGs, discovered via functional metagenomics). They found that acquired ARGs show strong geographic clustering (i.e., distinct regional patterns and stronger distance-decay within and between countries), whereas the FG ARGs were much more evenly distributed globally and their similarity decayed gradually over longer distances. The FG ARGs were also more tightly associated with particular bacterial taxa (i.e., embedded in native microbial communities) than acquired ARGs, indicating they may serve as a latent reservoir of resistance that has yet to mobilise widely. Their network analyses suggest that selection and ecological niche competition—not just physical dispersal—play major roles in shaping the global resistome, and they suggest that including FG ARGs in surveillance programmes could provide an early-warning for future resistance threats.