What is antibiotic resistance?

Antibiotic resistance is when bacteria develop the ability to survive exposure to antibiotics designed to kill them or stop their growth. 

What are antibiotics?

  • Antibiotics are medicines used to treat or prevent infections caused by bacteria.
  • They work by inhibiting the growth of or destroying the bacteria.
  • They do this in various ways, such as destroying the bacterial cell wall or inhibiting the generation of energy from glucose within the bacterial cell.

What is antibiotic resistance?

  • Antibiotic resistance occurs when bacteria develop the ability to survive exposure to antibiotics that were designed to kill them or stop their growth.
  • Antibiotic resistant bacteria are free to grow, multiply and cause infection within the host even when exposed to antibiotics.
  • Antibiotic resistance is a major obstacle in the treatment of infectious diseases caused by bacteria.
  • The result is that certain antibiotics can no longer be used to successfully treat certain infections.
  • This significantly affects our ability to prevent and treat these diseases, increasing recovery time, the length of time people stay in hospital and death rates.
  • Understanding the mechanisms by which bacteria become resistant to antibiotics is a key task in preventing the development and spread of antibiotic resistant bacteria.
  • Understanding these mechanisms will also be important in trying to prevent bacteria developing resistance to any new antibacterial treatments that may be produced in the future.

How does antibiotic resistance occur?

  • Antibiotic resistance occurs due to changes, or mutations, in the DNA of the bacteria, or the acquisition of antibiotic resistance genes from other bacterial species through horizontal gene transfer.
  • These changes enable the bacteria to survive the effects of antibiotics designed to kill them.
  • This means that when an antibiotic is used, all the bacteria that have not undergone a mutation are killed, while the antibiotic resistant bacteria remain unaffected.
  • The antibiotic resistant bacteria are able to continue to divide and grow producing even more bacteria that are not affected by the antibiotic.
  • The existence of resistant strains of bacteria means that antibiotics or drugs designed to kill them no longer work, allowing them to spread rapidly, posing a risk to public health.
  • When this happens it is necessary for scientists to develop new antibiotics that the bacteria do not have resistance to. 
Illustration showing how a population of bacteria can develop resistance to an antibiotic.

An illustration showing how a population of bacteria can develop resistance to an antibiotic.

Image credit: Genome Research Limited

Why is antibiotic resistance on the up?

  • Antibiotic resistance is a serious and growing problem in modern medicine.
  • The overuse of antibiotics in recent years has played a major role in increasing the prevalence of antibiotic resistant bacteria.
  • By frequently exposing bacteria to antibiotics it places a selection pressure on the bacteria that makes the emergence and spread of resistance much more likely.
  • Antibiotics are often prescribed for minor conditions that could easily get better on their own and patients often do not finish a course of antibiotics as prescribed by their doctors because their symptoms improve quickly.
  • To help prevent further emergence of antibiotic resistance, steps are being taken to ensure that antibiotics are only prescribed when there is a clear need for them and that they are used properly (the full course is taken).

This page was last updated on 2016-01-25