How Do Antibiotics Work?

Although there are a number of different types of antibiotic, they all work in one of two ways:

  • A bactericidal antibiotic (penicillin, for instance) kills the bacteria; these drugs usually interfere with either the formation of the bacterium’s cell wall or its cell contents
    A bacteriostatic stops bacteria from multiplying

What are antibiotics used for?

  • Antibiotics do not work against viruses.
  • An antibiotic is given for the treatment of an infection caused by bacteria. It is not effective against viruses.
  • If you have an infection, it is important to know whether it is caused by bacteria or a virus.
  • Most upper respiratory tract infections, such as the common cold and sore throats are caused by viruses – antibiotics do not work against these viruses.
  • If antibiotics are overused or used incorrectly, there is a risk that the bacteria will become resistant – the antibiotic becomes less effective against that type of bacterium.
  • A broad-spectrum antibiotic can be used to treat a wide range of infections. A narrow-spectrum antibiotic is only effective against a few types of bacteria. Some antibiotics attack aerobic bacteria, while others work against anaerobic bacteria. Aerobic bacteria need oxygen, anaerobic bacteria do not.
  • In some cases, antibiotics may be given to prevent rather than treat an infection, as might be the case before surgery. This is called ‘prophylactic’ use of antibiotics. They are commonly used before bowel and orthopaedic surgery.