Antimicrobial resistance: A one health metagenomic study of Indian tribal gut

• Source of drinking water shaped the resistome: individuals consuming stream water carried more metal, biocide, and multi-compound resistance, whereas tubewell water users had higher antibiotic resistance. • Individuals consuming stream water showed significantly greater resistome diversity and ecological enrichment. • Metal resistance genes were significantly overrepresented in microbial communities of individuals consuming stream water. • Environmental co-selective pressures, particularly exposure to heavy metals, shaped resistome dynamics even with minimal antibiotic use • Findings highlight the need for safe water access, environmental surveillance, and resistome-informed public health strategies. Antimicrobial resistance (AMR) is a global health threat driven by antibiotic misuse and environmental contamination. The human gut microbiome is a major reservoir of resistance genes, but its dynamics in populations with limited antibiotic exposure remain unclear. We applied a metagenomic One Health framework to profile the gut resistome of three Particularly Vulnerable Tribal Groups (Irula, Jenu Kuruba, and Kurumba) in South India. A total of 103 faecal samples were collected, with community DNA extracted and subjected to high-throughput shotgun metagenomic sequencing to detect resistance determinants. Analyses revealed pronounced inter-community differences: the Kurumba group exhibited the highest overall AMR burden, whereas the Irula group harboured the greatest diversity of non-antibiotic resistance classes. Drinking water source emerged as a major ecological driver of resistome composition. Individuals consuming untreated stream water displayed significantly elevated levels of metal (p = 4.2 × 10⁻⁸), biocide (p = 7.7 × 10⁻⁵), and multi-compound (p = 8.4 × 10⁻⁷) resistance, whereas tubewell water users showed higher antibiotic resistance (p=0.039). Diversity metrics confirmed that stream water consumers maintained more heterogeneous and ecologically enriched resistomes. Differential abundance analyses identified multiple metal resistance determinants significantly overrepresented in stream water-associated resistomes. To our knowledge, this is the first study in India demonstrating the ecological plasticity of the human gut resistome in marginalized tribal populations. These findings highlight the critical role of environmental co-selective pressures and underscore the urgent need for safe drinking water, systematic environmental surveillance, and integrative One Health interventions to mitigate AMR proliferation. provides a concise visual representation that encapsulates the key components and findings of the study.