Penicillin is a group of antibiotics derived from Penicillium fungi,
Penicillins are β-lactam antibiotics and are used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms.
Several enhanced penicillin families also exist, effective against additional bacteria: these include the antistaphylococcal penicillins, aminopenicillins and the more-powerful antipseudomonal penicillins.