<unk> s (P,<unk> N or<unk>  are a group of antibiotics originally obtained from<unk> m moulds, principally P. chrysogenum and P. rubens. Most<unk> s in clinical use are chemically synthesised from naturally-produced<unk> s. A number of natural<unk> s have been discovered, but only two purified compounds are in clinical use:<unk>  G (intramuscular or intravenous use) and<unk>  V (given by mouth).<unk> s 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. 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<unk> ; 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<unk>  are most often given cephalosporin C (another β-lactam antibiotic) because there is only 10% crossover in allergy between the<unk> s and cephalosporins.<unk>  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<unk>  to treat eye infection (ophthalmia neonatorum) in 1930. The purified compound<unk>  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<unk>  to treat streptococcal meningitis in 1942. For the discovery, Fleming shared the 1945 Nobel Prize in Physiology or Medicine with Florey and Chain. Several semisynthetic<unk> s are effective against a broader spectrum of bacteria: these include the antistaphylococcal<unk> s, aminopenicillins and the antipseudomonal<unk> s.
Penicillin
Carbenicillin
Extended-spectrum penicillin
Tetracycline
Phenoxymethylpenicillin
Benzylpenicillin
Piperacillin
Methicillin