Antibiotic-resistant infections annually claim hundreds of thousands of lives worldwide. This problem is exacerbated by exchange of resistance genes between pathogens and benign microbes from diverse habitats. Mapping resistance gene dissemination between humans and their environment is a public health priority. Here we characterized the bacterial community structure and resistance exchange networks of hundreds of interconnected human faecal and environmental samples from two low-income Latin American communities. We found that resistomes across habitats are generally structured by bacterial phylogeny along ecological gradients, but identified key resistance genes that cross habitat boundaries and determined their association with mobile genetic elements. We also assessed the effectiveness of widely used excreta management strategies in reducing faecal bacteria and resistance genes in these settings representative of low- and middle-income countries. Our results lay the foundation for quantitative risk assessment and surveillance of resistance gene dissemination across interconnected habitats in settings representing over two-thirds of the world’s population. An analysis of bacterial community structure and antibiotic resistance gene content of interconnected human faecal and environmental samples from two low-income communities in Latin America was carried out using a combination of functional metagenomics, 16S sequencing and shotgun sequencing; resistomes across habitats are generally structured along ecological gradients, but key resistance genes can cross these boundaries, and the authors assessed the usefulness of excreta management protocols in the prevention of resistance gene dissemination. Mapping the distribution and dissemination of antibiotic resistance genes is a public health priority. Gautam Dantas and colleagues have characterized the bacterial community structure and resistance gene exchange networks from two low-income Latin American communities — a rural village of subsistence farmers 35 km south of San Salvador, El Salvador and a shanty town in the desert hills about 15 km southwest of Lima, Peru. Using functional genomics and whole-metagenome sequencing of hundreds of interconnected human faecal and environmental samples, the authors find that resistomes across habitats are generally structured by bacterial phylogeny along ecological gradients, but that key resistance genes can cross these boundaries. They also assess the usefulness of excreta management protocols in the prevention of resistance gene dissemination. Collectively, this work lays the foundation for quantitative risk assessment and surveillance of antibiotic resistance gene transmission across diverse environments.

Interconnected microbiomes and resistomes in low-income human habitats