Antibiotics are substances that slow down or stop the growth of bacteria. They are commonly prescribed medicines, examples include penicillin and amoxicillin.

Antibiotics are only effective against bacterial diseases and not viral ones.


From under a microscope, penicillin eroding a bacterial cell.
A bacterial cell damaged by penicillin

Penicillin was the first antibiotic discovered in 1928 by Alexander Fleming. He noticed that some bacteria he had left in a petri dish had been killed by the naturally occurring Penicillium fungus. The fungus was then mass produced in batch fermenters and the antibiotic extracted and purified for use in humans.

Antibiotics are now often chemically modified and so are semi-synthetic or synthetic.

How do antibiotics work?

Antibiotics damage the bacterial cells but do not damage the host cells - as they attack the bacterial or fungal cell wall. They have the ability to cure some bacterial diseases that would have previously killed many people. Since their introduction, they have had a large influence on the world's health and death rate.

Different bacteria cause different diseases. One antibiotic may only work against one type of bacteria, or a few types. This means that a range of different antibiotics is needed for the treatment of the whole range of bacterial diseases.

Antibiotic Resistance

Since Penicillin was discovered in 1928, the use of antibiotics for the treatment of diseases has increased exponentially. Antibiotics are being overused in many ways in our world today.

Problems with antibiotics

Commonly prescribed antibiotics are becoming less effective due to a number of reasons:

  • Over use of antibiotics - people feel unwell and when going to the doctors, they expect antibiotics to be prescribed. If patients have viral infections such as the common cold and not a bacterial one, the antibiotics are ineffective and unnecessary. Using antibiotics when not necessary kills non-resistant bacteria providing ideal conditions for the growth of antibiotic resistant bacteria.
  • Failing to complete the fully prescribed course by a doctor - patients should always fully complete the prescribed course of antibiotics, every time they are taken. This ensures all non-resistant bacteria are killed and the immune system is able to remove any resistant bacteria present.
  • Use of antibiotics in farming - previously antibiotics were regularly used in farming and these can be used to prevent disease, keep the animals well and allow them to grow quickly. This could lead to spread of antibiotic resistance from animals into human hosts. Legal controls are now in place to try and reduce the use of antibiotics in this way.

The use of antibiotics shown above can lead to the effectiveness of antibiotics being reduced and the incidence of antibiotic resistance increasing.

Bacteria which are resistant to the antibiotics normally used to kill them are commonly known as 'superbugs'. MRSA is one of these antibiotic resistant bacteria. It is important that there are control measures in place to prevent the spread of this disease.

MRSA control measures include:

  • hand washing
  • thorough cleaning of hospital wards
  • use of alcohol gels
  • MRSA screening

The future

The development of all drugs, including antibiotics, is a costly and time-consuming process. In recent years, we have been unable to develop lots of different new antibiotics. People are concerned that soon some bacteria will be resistant to all known antibiotics and that the development of new ones will take too long.