Microbes without borders: how antibiotics reshape the microbial worlds we depend on

For World Microbiome Day, the PEOPLE AMR Network highlights how antimicrobial resistance (AMR) moves between people, animals and the environment and why protecting antibiotics means protecting the microbial worlds we share.

World Microbiome Day celebrates the trillions of microbes that make life possible. Microbes are often seen only as germs to avoid, but most are essential partners in health. The human gut hosts trillions of microorganisms that help train the immune system, synthesise vitamins, digest food and protect against harmful pathogens. Microbial communities also sustain healthy soils, animals, rivers, farms and ecosystems. 

Antibiotics are among the greatest medical discoveries ever made. They save lives and underpin surgery, cancer treatment, childbirth and intensive care. But antibiotics do not only affect the infection they are prescribed to treat. They also disrupt the beneficial microbial communities that World Microbiome Day exists to celebrate.

A single course of antibiotics can significantly reduce gut bacterial diversity, and some species may take months to recover – if they recover at all. When antibiotic residues reach soil and waterways through agricultural runoff or wastewater, they can alter the microbial communities that cycle nutrients, purify water and maintain healthy ecosystems. This damage can make it easier for resistant bacteria to survive, multiply and share resistance genes.

AMR occurs when bacteria evolve ways to survive antibiotics that once killed them. As resistance spreads, infections become harder to treat, procedures become riskier and modern medicine is threatened. AMR is not confined to hospitals. Resistant bacteria and resistance genes can move between people, animals, food systems, wastewater, soils and rivers. A resistant bacterium does not recognise boundaries between human, animal and environmental health.

People are central to this challenge. When a patient takes antibiotics for a viral infection that won't respond to them, the drug still reshapes their gut microbial community. When antibiotics are used routinely in farming, they alter the microbial ecology of soil and water. When leftover medicines are discarded or antimicrobial residues enter wastewater, they create pressure on microbial communities far from the original point of use. Healthcare access, illness management, farming practices, economic pressures and public understanding shape these decisions – which is why understanding human behaviour is as important to protecting microbiomes as understanding microbiology.

AMR requires a 'One Health' approach that recognises connections between people, animals and the environment. It also requires social and behavioural insight. The PEOPLE AMR Network brings together microbiology, health research, veterinary and environmental expertise with social science and behavioural science. Its role is to understand not only how resistance spreads, but why antibiotics are used in particular ways, and how responsible decisions can be supported.

World Microbiome Day reminds us that antimicrobial stewardship is about more than preserving medicines. It is about protecting the microbial ecosystems that support life and health across humans, animals and the environment. By building evidence, partnerships and practical understanding, the PEOPLE AMR Network is helping to tackle AMR, safeguard beneficial microbiomes and preserve antibiotics for future generations.

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