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Toolbox  –  Understand

Antibiotics

What are antibiotics?

Antibiotics are important medicines for the treatment of bacterial infections in humans and animals. Since their introduction in the 1940’s antibiotics have saved countless lives and has made many medical techniques possible or safer.

Difference between antimicrobials and antibiotics

There are many different compounds that can inhibit the growth of microorganisms, and many terms that are used to categorize such compounds. ‘Antimicrobials‘, ‘antibacterials’ and ‘antibiotics’ are commonly used terms that can sometimes be used interchangeably, but there are important differences between these words:

  • Antimicrobials is a wider term that includes all agents that act against microorganisms, namely bacteria, fungi, viruses and protozoa.
  • Antibacterials act only on bacteria. Broadly defined, this term encompasses all compounds that act against bacteria, including antibiotics. Today the term is sometimes used for different types of disinfectants that are not used as medicine, such as alcohol or triclosan.
  • Antibiotics are produced naturally by microorganisms and kill or inhibit the growth of other microorganisms, mainly bacteria. The word comes from the Greek words ‘anti’, meaning ‘against’, and ‘biotikos’, meaning ‘concerning life’. Strictly speaking, antibiotics do not include agents that are produced by chemical or biochemical synthesis. However for simplicity, synthetic or semi-synthetic variants (such as quinolones) are usually included under the term antibiotics. In this Toolbox, the term antibiotic is used for naturally produced and synthetic compounds that are active against bacteria, mainly those that have been approved for treatment of bacterial infections in humans and/or animals.
Summary diagram of the different types of antimicrobials and their activity: antibiotics, antivirals, antiparasitic agents and antifungals.
Figure 1. Different types of antimicrobials and the microorganisms they are active against.

Antibiotics act on bacteria, not viruses

Antibiotics are mainly active against bacteria, but can also have activity against for example some parasites. They do not cure infections caused by viruses. Below are some examples of bacterial and viral infections:

Bacterial infections Viral infections (antibiotics do not work!)
Bacterial pneumonia Colds
Sepsis (blood stream infections) Most respiratory tract infections
Wound and skin infections Influenza (the flu)
Urinary tract infections Viral gastroenteritis
Bacterial tonsillitis (strep throat) Measles