Penicillins (P, PCN or PEN) are a group of antibiotics originally obtained from Penicillium moulds, principally P. chrysogenum and P. rubens.
Most penicillins in clinical use are chemically synthesised from naturally-produced penicillins. A number of natural penicillins have been discovered, but only two purified compounds are in clinical use: penicillin G (intravenous use) and penicillin V (given by mouth).
Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are members of the β-lactam antibiotics, which are some of the most powerful and successful achievements in modern science.
They are still widely used today for different bacterial infections, though many types of bacteria have developed resistance following extensive use.
About 10% of people report that they are allergic to penicillin; however, up to 90% of this group may not actually be allergic. Serious allergies only occur in about 0.03%. Those who are allergic to penicillin are most often given cephalosporin C (another β-lactam antibiotic) because there is only 10% crossover in allergy between the penicillins and cephalosporins.
Penicillin was discovered in 1928 by Scottish scientist Alexander Fleming as a crude extract of P. rubens.
Fleming's student Cecil George Paine was the first to successfully use penicillin to treat eye infection (ophthalmia neonatorum) in 1930. The purified compound (penicillin F) was isolated in 1940 by a research team led by Howard Florey and Ernst Boris Chain at the University of Oxford.
Fleming first used the purified penicillin to treat streptococcal meningitis in 1942.[5] For the discovery, Fleming shared the 1945 Nobel Prize in Physiology or Medicine with Florey and Chain.
There are several semi-synthetic penicillins which are effective against a broader spectrum of bacteria: these include the antistaphylococcal penicillins, aminopenicillins and the antipseudomonal penicillins.