Historically, the most famous of all antibiotics, named for the fungal mould Penicillium notatum from which it is derived. Penicillin acts by destroying the cell wall in those bacteria that are sensitive have been developed (not resistant) to its actions. Penicillin is active against Streptococci (including Streptococcus pneumoniae), Listeria, Neisseria gonorrhoea, Clostridium, Peptococcus, and Peptostreptococcus. Most staphylococci now are resistant to penicillin. Today, many derivatives of penicillin are available which act on more types of bacteria than is penicillin itself. The name "penicillium" was taken from the Latin "penicillum" meaning "a painter's brush" because the fronds of the fungus were thought to look like a painter's brush. Chicken soup, long known as "Jewish penicillin," may in reality have some therapeutic merit. The History of Penicillin: The discovery of penicillin was one of the major events in the history of medicine. In 1871 the scientist Joseph Lister by chance noticed that the mould which grows on cheese and fruit can make microbes (germs) grow weaker. He made some successful experiments on patients but did not, it seems, fully recognize the implications of his findings. In 1906 the young physician Alexander Fleming became a research assistant at St Mary's Hospital in London. Fleming went to France during the First World War to treat wounded soldiers and could see for himself that there was no effective way of treating many infections. Back at St Mary's after the war, Fleming was determined to find a better way of killing germs. In 1928 he was studying staphylococci bacteria (that can, among other things, infect wounds). By pure luck, he noticed that on a dish containing agar on which he had been growing germs, near some mould, the germs were less common. He grew more of the mould, naming it penicillin from its Latin name Penicillium. Fleming discovered the mould was effective against bacteria that caused diseases such as anthrax, meningitis and diphtheria. He published his discoveries but did not have the resources to experiment more widely with penicillin. In 1938 Howard Florey, professor of pathology at Oxford University, started work on some of the mould that Fleming had grown. Florey was an Australian doctor who had already made a number of important discoveries and was also studying natural substances that could kill bacteria. He had been impressed by an article that Fleming had published in 1929 describing the effects of penicillin. Unlike Fleming, Florey had a large research department, including Ernst Chain, a German Jew who had fled the Nazis.
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1. Originally, an antibiotic substance obtained from cultures of the molds Penicillium notatum or P. chrysogenum; interferes with cell wall synthesis in bacteria. 2. One of a family of natural or synthetic variants of penicillic acid. They are mainly bactericidal in action, are especially active against Gram-positive organisms, and, with the exception of hypersensitivity reactions, show a particularly low toxic action on animal tissue. [see penicillus]
- aluminum p. the trivalent aluminum salt of an antibiotic substance or substances produced by the growth of the molds Penicillium notatum or P. chrysogenum; used for oral or sublingual administration.
- p. amidase an enzyme that catalyzes the hydrolysis of the amide bond in the penicillins, producing a carboxylic acid anion and penicin; penicin is the precursor of many synthetic penicillins.
- benzyl p. SYN: p. G.
- buffered crystalline p. G crystalline potassium p. G or crystalline sodium p. G buffered with not less than 4% and not more than 5% of sodium citrate.
- chloroprocaine p. O a crystalline salt of 2-chloroprocaine and p. O, insoluble in water; the level of the antibiotic in the blood persists for 24 hours; its antibacterial activity is similar to that of p. O and G.
- p. G a commonly used p. compound; it comprises 85% of the p. salts: sodium, potassium, aluminum, and procaine, with the latter exerting prolonged action on intramuscular injection, because of limited solubility. An antibiotic obtained from the mold Penicillium chrysogenum used orally and parenterally; primarily active against Gram-positive staphylococci and streptococci; destroyed by bacterial β-lactamase. SYN: benzyl p., benzylpenicillin.
- p. G benzathine a relatively insoluble preparation that may remain in the body for 1–2 weeks.
- p. G hydrabamine a dipenicillin compound, a mixture of p. G salts consisting chiefly of the salt of the diacidic base N,N ′-bis-(dehydroabietyl) ethylenediamine.
- p. G potassium the potassium salt of p. G, containing 85–90% p. G.
- p. G procaine the procaine salt of p. G; it has a more prolonged action than p. G.
- p. G sodium the sodium salt of p. G, containing not less than 85% p. G.
- p. N SYN: cephalosporin N.
- p. O produced by growing the mold in a medium containing allylmercaptomethylacetic acid; also available as the potassium and sodium salts. SYN: allylmercaptomethylpenicillin.
- p. phenoxymethyl SYN: p. V.
- p. V a p. derivative containing a phenoxyacetyl group; obtained from Penicillium chrysogenum Q 176; a crystalline nonhydroscopic acid, very stable even in high humidity; it resists destruction by gastric juice; the potassium salt is used orally; precursor for the synthesis of analogs of cephalosporin C. SYN: p. phenoxymethyl, phenoxymethylpenicillin.
- p. V benzathine p. for oral use.
- p. V hydrabamine a compound with preparation and uses analogous to those of p. G hydrabamine.

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pen·i·cil·lin .pen-ə-'sil-ən n
1) a mixture of relatively nontoxic antibiotic acids produced esp. by molds of the genus Penicillium (as P. notatum or P. chrysogenum) and having a powerful bacteriostatic effect against various chiefly gram-positive bacteria (as staphylococci, gonococci, pneumococci, hemolytic streptococci, or some meningococci)
2) any of numerous often hygroscopic and unstable amido acids (as penicillin G, penicillin O, and penicillin V) that have a structure in which a four-membered lactam ring shares a nitrogen and a carbon atom with a thiazolidine ring to which it is fused and that are components of the penicillin mixture or are produced biosynthetically by the use of different strains of molds or different media or are synthesized chemically
3) a salt or ester of a penicillin acid or a mixture of such salts or esters

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an antibiotic that was derived from the mould Penicillium rubrum and first became available for treating bacterial infections in 1941. Since then, a number of naturally occurring penicillins have been developed to treat a wide variety of infections, notably penicillin G (benzylpenicillin), usually administered by injection but taken orally to treat dental abscesses, and penicillin V (phenoxymethylpenicillin), which is administered orally. There are few serious side-effects, but some patients are allergic to penicillin and develop such reactions as skin rashes, swelling of the throat, and fever. There are many antibiotics that are derived from the penicillins, including amoxicillin, ampicillin, and flucloxacillin; these are known as semisynthetic penicillins. All penicillins are beta-lactam antibiotic and are sensitive to penicillinase.

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pen·i·cil·lin (pen″ĭ-silґin) any of a large group of natural or semisynthetic antibacterial antibiotics derived directly or indirectly from strains of fungi of the genus Penicillium and other soil-inhabiting fungi grown on special culture media, which exert a bacteriocidal as well as a bacteriostatic effect on susceptible bacteria by interfering with the final stages of the synthesis of peptidoglycan, a substance in the bacterial cell wall. The penicillins, despite their relatively low toxicity for the host, are active against many bacteria, especially gram-positive pathogens (streptococci, staphylococci, pneumococci); clostridia; some gram-negative forms (gonococci, meningococci); some spirochetes (Treponema pallidum and T. pertenue); and some fungi. Certain strains of some target species, e.g., staphylococci, secrete the enzyme penicillinase, which inactivates penicillin and confers resistance to the antibiotic.

Medical dictionary. 2011.

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  • penicillin — pen i*cil lin, n. [From Penicillium, the fungus genus from which it was first isolated.] (Chem.) Any of a variety of substances having a structure containing a beta lactam ring fused to a thiirane ring, to which a carboxyl group is attached, most …   The Collaborative International Dictionary of English

  • penicillin G — penicillin pen i*cil lin, n. [From Penicillium, the fungus genus from which it was first isolated.] (Chem.) Any of a variety of substances having a structure containing a beta lactam ring fused to a thiirane ring, to which a carboxyl group is… …   The Collaborative International Dictionary of English

  • penicillin G — jē n the penicillin C16H18N2O4S that constitutes the principal or sole component of most commercial preparations and is used chiefly in the form of its stable salts (as the sodium salt C16H17N2NaO4S or potassium salt C16H17KN2O4S) called also… …   Medical dictionary

  • penicillin V — vē n a crystalline nonhygroscopic acid that is used in the form of its potassium salt C16H17KN2O5S and has antibacterial action similar to penicillin G and is more resistant to inactivation by gastric acids called also phenoxymethyl penicillin *… …   Medical dictionary

  • Penicillin — Sn (ein Antibiotikum) erw. fach. (20. Jh.) Entlehnung. Entlehnt aus ne. penicillin, dieses aus l. Penicillium notatum, dem Namen eines Schimmelpilzes, aus l. pēnicillium Pinsel, Wundfäden, gezupfte Leinwand , einem Diminutivum zu l. pēniculus m.… …   Etymologisches Wörterbuch der deutschen sprache

  • penicillin O — ō n a penicillin C13H18N2O4S2 that is similar to penicillin G in antibiotic activity but that is obtained by growing the penicillia in a culture medium that contains a precursor …   Medical dictionary

  • penicillin F — ef n a penicillin C14H20N2O4S that was the first of the penicillins isolated in Great Britain …   Medical dictionary

  • Penicillin U — См. Пенициллин U (Источник: «Словарь терминов микробиологии») …   Словарь микробиологии

  • penicillin — penicillin. См. пенициллин. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Penicillin — Penicillin, erstes ⇒ Antibiotikum; 1923 von Alexander Fleming als gegen grampositive Eubakterien wirksames Peptid entdeckt. P. wird von Arten des Pinselschimmels Penicillium produziert; es konnte erst 1940 isoliert werden. Die Wirksamkeit der… …   Deutsch wörterbuch der biologie

  • penicillin — 1929, coined in English by Alexander Fleming (1881 1955), who first recognized its antibiotic properties, from Mod.L. Penicillium notatum (1867), the name of the mould from which it was first obtained, from L. penicillus paintbrush (see PENCIL… …   Etymology dictionary

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