About antibiotic resistance

Infections become drug-resistant when the bacteria that cause them adapt and change over time, developing the ability to resist the drugs designed to kill them. The result is that many drugs – like antibiotics – are becoming less effective at treating illnesses. Our overuse of antibiotics in both humans and animals is speeding up this process.

Antibiotics do not work as well as they used to

Antibiotics have transformed our ability to treat bacterial infections allowing us to live healthier, longer lives. But antibiotic overuse makes bacteria evolve so they can survive the effects of antibiotics. This is known as ‘antibiotic resistance’.

By 2050, 10 million people per year could die as a result of bacterial infections that cannot be treated with antibiotics. If we do nothing now we could face a future where the antibiotics that we take for granted today no longer work. It will become harder to treat common infections, and procedures that rely on antibiotics, like chemotherapy or even hip-replacements will become risky.

The year 2050 seems a long way off, but drug-resistant infections are affecting people now. It’s been estimated, for instance, that antibiotic resistance affected around 53 000 people in the UK in 2015, of which more than 2000 died.

These numbers can hide the fact that antibiotic resistance affects all sorts of people at a personal level. The vast majority of these people don’t die, but they may be sick for longer, need longer treatments or have more side-effects. You can read about how antibiotic resistance is affecting some of those people here.

So what is antibiotic resistance?

You’ll often see headlines about antibiotic resistance in the press. Most people will say that they know what antibiotic resistance is, but they often don’t get it right – it’s a slippery concept. Have a go at testing your understanding below:


Below you’ll see some statements made by members of the public who were asked to describe what they understood by the term antibiotic resistance.

Which do you think are correct?

  • If you rely too much on antibiotics then your body gets used to them.
  • If you take too much of anything then eventually you become immune to it.
  • It’s your tolerance level. Your body has adapted to it.

All of these statements about antibiotic resistance are false.

Your body can become used to or tolerant to some drugs. Alcohol is a good example of this. If you drink regularly, your body will start to produce enzymes that break the alcohol molecules down quickly. The pint of beer that made you tipsy when you first started drinking, will have very little effect after you’ve been drinking for any length of time.

Antibiotic resistance is not the same thing. It’s not your body that becomes resistant to the antibiotics it’s the bacteria themselves that become resistant to the antibiotics.

It’s an important distinction. You can get an infection with an antibiotic resistant bacteria even if you have never had an antibiotic, for instance by picking it up from another person.

Antibiotic resistance, then, is not the process whereby your body becomes tolerant to, gets used to or immune to antibiotics. Antibiotic resistance refers to the process whereby bacteria become resistant to the antibiotics that we use to treat and prevent infections is they are no longer killed or prevented from reproducing by the antibiotics.

How do bacteria become resistant to antibiotics?

Your body is teeming with bacteria. Your gut, for instance, contains around 100 trillion bacteria. Most of these bacteria are harmless and may even be necessary for good health. There will be some bacteria as well that can cause disease but your body usually keeps these in check. Antibiotics can upset the balance between “good” and “harmful” bacteria. Problems occur when bacteria get into parts of the body where they are not supposed to be found, like the bladder or the bloodstream

Urine infections: An example of infection commonly resistant to antibiotics today

If you had a urine infection until very recently, the chances are your GP would have given you trimethoprim. First developed in 1962, it came onto the UK market in 1968 and was widely used as a treatment for urine infections caused by E. coli (the most common cause of urine infections). The first record of E.coli that were resistant to trimethoprim in the UK was in 1972. By the 2010s 34% of E. coli urine infections were resistant to trimethoprim. Because of this trimethoprim is no longer recommended as the first treatment for urine infections.

What factors lead to antibiotic resistance?

Antibiotics are not only used in humans. They are also used in pets and farm animals, in fish, in agriculture and in food production. This means that the way antibiotic resistance occurs is complicated involving humans, animals and the environment. But, as you might expect, one of the main reasons for the development of antibiotic resistance is the amount of antibiotics used. The greater the quantity of antibiotic used the, greater the likelihood of antibiotic resistance.

This is why the PASS project focuses on improving antibiotic prescribing, and reducing the number of people who get treated with antibiotics when they do not need them.

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