Why are bacteria becoming resistant to antibiotics, and what can be done about it?

Antibiotic resistance is evolution by natural selection happening fast enough¹ for us to watch.

In any large population of bacteria, random mutations mean a few may happen to survive a particular antibiotic — perhaps they have an enzyme that breaks it down or a pump that removes it. When we use the antibiotic, it kills the susceptible bacteria and leaves the resistant ones with less competition, so they multiply. Bacteria can also share resistance genes directly with each other on plasmids², which means resistance can spread between different species.

Anything that increases the use of antibiotics increases this selection pressure: prescribing them for viral infections where they don't help, using them heavily in farming, and poor infection control in hospitals allowing resistant bacteria to spread.

It matters because modern medicine depends on antibiotics — not just for infections but to make surgery, chemotherapy and caesarean sections safe.

Solutions work at several levels: prescribers using antibiotics only when needed and choosing narrow-spectrum drugs — known as stewardship; better rapid tests so we know when they're needed; infection prevention like hand hygiene and vaccination, which reduces infections in the first place; and regulating agricultural use. New antibiotics are also needed, but they're commercially unattractive because we'd want to use them as little as possible³, so governments are experimenting with different ways to pay for them.