Antibiotic resistance

Antibiotic resistant infections can affect anyone of any age and are a growing health problem around the world. Antibiotic resistant infections lead to higher medical costs, longer hospital stays and, sometimes, death.

Key points

  1. Antibiotic resistance occurs when bacteria change (or mutate) so that antibiotics no longer work to treat infections. 
  2. The failure of these common antibiotics means other medications have to be used, which are often more costly and can have more serious side effects.
  3. There is also the risk that infections that have for many years been easily managed may once again become untreatable and uncontrollable.
  4. Preventing infection and appropriate use of antibiotics are key ways of fighting antibiotic resistance.

What is antibiotic resistance?

Antibiotic resistance occurs when bacteria change (or mutate) so that antibiotics no longer work to treat infections. Usually, the more often antibiotics are used, the more bacteria adapt and find new ways to survive, which means they become resistant to antibiotics. Instead of being killed by the antibiotics, some bacteria survive and continue to multiply, causing more harm. Using antibiotics when they’re not needed drives bacteria to become more resistant. 

What causes antibiotic resistance?

The main causes of antibiotic resistance are the misuse and over-use of antibiotics. 

  • Antibiotics are one of the most commonly prescribed medications.
  • Up to 50% of all antibiotics prescribed for people are not needed or not taken effectively.
  • Antibiotics are also often used in food for animals to prevent, control and treat disease and to promote growth.
  • This can lead to antibiotic resistance in humans because drug-resistant bacteria can remain on meat. When not handled or cooked properly, the bacteria can spread to humans.  

How does antibiotic resistance happen?

Bacteria can become resistant to antibiotics in several ways.

  • Some bacteria can change their outer structure so the antibiotic has no way to attach to the bacteria it is intended to kill.
  • Some bacteria can ‘neutralise’ an antibiotic by changing it in a way that makes it ineffective.
  • Others have mechanisms that pump an antibiotic back outside of the bacteria before it can work.
  • Bacteria can also become resistant through mutation of their genetic material. After being exposed to antibiotics, sometimes bacteria can survive by finding a way to resist the antibiotic. If even one bacterium becomes resistant to an antibiotic, it can then multiply and replace all the bacteria that were killed off.

Image credit: PHARMAC, NZ

The spread of antibiotic resistance occurs when resistant strains of bacteria are passed from person to person and from non-human sources in the environment, including food.

What does antibiotic resistance mean for you, your whānau and the community?

Antibiotic resistance is a major concern because it means some infections will become more difficult, and sometimes impossible, to treat. If you or someone in your family develop an antibiotic-resistant infection:

  • you may have the infection for longer
  • you may be more likely to have complications from the infection
  • you could remain infectious for longer and pass your infection to other people.

Infections caused by antibiotic-resistant bacteria are harder to treat, usually last longer, often result in longer stays in hospital and are associated with more complications. In serious cases they can cause death.

Doctors have to use to less conventional antibiotics or a combination of different antibiotics to treat these infections. These are usually more costly and can have more-serious side effects.

In Aotearoa New Zealand, the occurrence of antibiotic-resistant bacteria is increasing. Examples of antibiotic-resistant bacteria include:

  • Methicillin-resistant Staphylococcus aureus (MRSA) – a group of bacteria (called Staphylococcus aureus) that are resistant to commonly used penicillin-like antibiotics
  • Extended spectrum beta-lactamases (ESBL) – chemicals produced by some bacteria that prevent certain antibiotics from working.
  • Vancomycin-resistant enterococci (VRE) – a group of bacteria (called enterococci) that are resistant to the antibiotic vancomycin.  

How can antibiotic resistance be prevented?

Preventing infections and their spread helps stop antibiotic resistance by reducing the need for antibiotics. Key things you can do are to regularly wash your hands and keep up to date with vaccinations.

Using antibiotics appropriately can also prevent antibiotic resistance. This includes:

  • taking them as you are advised by your healthcare provider
  • only taking antibiotics if they are prescribed for you
  • not using or sharing leftover antibiotics
  • taking any unused antibiotics to your pharmacy so they are disposed of safely.

Read more about how to prevent antibiotic resistance.

Antimicrobial resistance - STUDENT PRIZE of the Health for All Film Festival

(World Health Organization, 2020)

Learn more

Your family and antibiotics – what you need to know Pharmac, NZ
Antimicrobial resistance
Ministry of Health, NZ
Drug infections are hard to treat (MaoriRoyal Society, Te Aparangi, NZ  
Keeping antibiotics effective, with your help Canterbury District Health Board, NZ
Antibiotics can help, but they can also harm Canterbury District Health Board, NZ
Your health is very important to us Canterbury District Health Board, NZ 


  1. Antibiotic Amnesty Frequently Asked Questions Pharmaceutical Society of New Zealand (PSNZ) 
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 15 Nov 2017