<P> Penicillin (PCN or pen) is a group of antibiotics which include penicillin G (intravenous use), penicillin V (use by mouth), procaine penicillin, and benzathine penicillin (intramuscular use). Penicillin antibiotics were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci . They are still widely used today, though many types of bacteria have developed resistance following extensive use . </P> <P> 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% . All penicillins are β - lactam antibiotics . </P> <P> Penicillin was discovered in 1928 by Scottish scientist Alexander Fleming . People began using it to treat infections in 1942 . There are several enhanced penicillin families which are effective against additional bacteria; these include the antistaphylococcal penicillins, aminopenicillins and the antipseudomonal penicillins . They are derived from Penicillium fungi . </P> <P> The term "penicillin" is often used generically to refer to benzylpenicillin (penicillin G, the original penicillin found in 1928), procaine benzylpenicillin (procaine penicillin), benzathine benzylpenicillin (benzathine penicillin), and phenoxymethylpenicillin (penicillin V). Procaine penicillin and benzathine penicillin have the same antibacterial activity as benzylpenicillin but act for a longer period of time . Phenoxymethylpenicillin is less active against gram - negative bacteria than benzylpenicillin . Benzylpenicillin, procaine penicillin and benzathine penicillin can be given by intravenous or intramuscular injections, but phenoxymethylpenicillin can be given by mouth because of its acidic stability . </P>

When was penicillin first used on a large scale basis