Antibiotics are medicines that treat infections and diseases caused by bacteria. They have been so widely used since they were introduced in the 1940s that they don't work as well any more against some bacteria.
What are antibiotics?
Antibiotics damage bacteria so the body’s immune system can fight them. They do not work against viruses.
Different antibiotics work against different bacteria. Penicillin is an example of an antibiotic. Sometimes, doctors choose an antibiotic based on what they believe will work. At other times, doctors will perform tests to work out which bacteria are causing the infection, and which antibiotics are likely to be effective against them.
Many antibiotics are less effective than they once were due to bacteria becoming resistant to their effects. This is called antibiotic resistance. Antibiotics should only be used if they are needed to treat a bacterial infection.
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Last reviewed: May 2020