Antibiotics and drug testing
Antibiotics are substances that kill bacteria [bacteria: Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium. ] or prevent their growth. They do not work against viruses [viruses: ultramicroscopic non-cellular organisms that replicate themselves inside the cells of living hosts ]. It is difficult to develop drugs that kill viruses without damaging the body’s tissues.
The first antibiotic, penicillin, was discovered by Alexander Fleming in 1928. He noticed that some bacteria he had left in a Petri dish had been killed by naturally occurring penicillium mould.
Since the discovery of penicillin, many other antibiotics have been discovered or developed. Most of those used in medicine have been altered chemically to make them more effective and more safe for humans.