Penicillin is an antibiotic used to treat a variety of bacterial infections. It was discovered in 1928 by Alexander Fleming and has since become one of the most widely used antibiotics in the world. Penicillin works by inhibiting the growth of bacteria, preventing them from reproducing and causing
Penicillins are a group of β-lactam antibiotics originally obtained from Penicillium moulds, principally P. chrysogenum and P. rubens. Most penicillins in clinical use are synthesised by P. chrysogenum using deep tank fermentation and then purified. A number of natural penicillins have been discovered, but only two purified compounds are in clinical use: penicillin G and penicillin V. Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are still widely used today for various bacterial infections, though many types of bacteria have developed resistance following extensive use.