What is antibiotic resistance?

Antibiotic resistance occurs when your bacterial infection no longer responds to treatment from antibiotics.

If you suffer food poisoning, get a serious cut, or a bacterial infection – such as a urinary tract infection (UTI) – your doctor may prescribe antibiotics to weaken and kill the microbes causing the symptoms.

These microbes have evolved over tens of millions of years to be effective at infecting humans. They continually develop different ways to evade the body’s immune system.

In the constant battle to get better and overcome the evolutionary defences that humans developed, microbes didn’t count on Alexander Fleming discovering penicillin in 1928. Humans had a new weapon to treat infections; and then another and another as scientists built on that work to discover new antibiotics.



Problem solved?

But microbes can replicate very quickly. For example, E. coli can replicate every 20 minutes producing a new generation with the potential to be resistant to some antibiotics.

We had a head start, but microbes can divide and learn much faster than we can develop new antibiotics.

By 1942, the first penicillin-resistant infections caused by the bacteria staphylococcus aureus started to appear.

Now, there are strains which are resistant to our more commonly used antibiotics, meaning doctors have fewer and fewer antibiotics left to treat patients effectively. This is called antibiotic (or antimicrobial) resistance – or AMR.

Using antibiotics inappropriately, like taking them for a viral infection or not competing the full course to totally eradicate the infection, give microbes opportunities to try out the new defences they’ve taught themselves. The more we misuse antibiotics, the better microbes get at resisting them.

And so, the more we use our last lines of defence – the most effective antibiotics in our arsenal – the more opportunities we are presenting to microbes to outwit us.

Last modified: 20 September 2023

Last reviewed: 20 September 2023