Antibiotics are chemicals produced by or derived from microoganisms (i.e. bugs or germs such as bacteria and fungi), that kill or prevent the growth of other bugs and germs. Antibiotics are a specific type of antimicrobial drug. However, the term antibiotic is now widely used to refer to all drugs that selectively target bacteria.
Penicillin was the first antibiotic to be discovered by Sir Alexander Fleming in 1928. However, it wasn't widely used until the Second World War. Following the success of penicillin many bugs were screened to see if they produced antibiotics that could be used in medicine. This successfully identified more antibiotics. Now, new methods are needed to develop new antibiotics, but this is an expensive and time-consuming process for drug companies.