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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. Penicillins 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. Despite their relatively low toxicity for the host, they are active against many bacteria, especially gram-positive pathogens (streptococci, staphylococci, pneumococci); clostridia; certain gram-negative forms (gonococci and meningococci); certain spirochetes (Treponema pallidum and T. pertenue); and certain fungi. Certain strains of some target species, for example staphylococci, secrete the enzyme penicillinase, which inactivates penicillin and confers resistance to the antibiotic. Some of the newer penicillins, such as methicillin, are more effective against penicillinase-producing organisms. A class of extended-spectrum penicillins includes piperacillin and mezlocillin.

Penicillin is administered intramuscularly, orally, in liquid or tablet form, and topically in ointments. Oral administration requires larger doses of the drug because absorption is incomplete. Allergic reactions occur in some persons. The reaction may be slight—a stinging or burning sensation at the site of injection—or it can be more serious—severe dermatitis or even anaphylactic shock, which may be fatal.
penicillin G the most widely used penicillin, used principally in the treatment of infections due to gram-positive organisms, gram-negative cocci, Treponema pallidum and Actinomyces israelii. The usual forms are salts such as penicillin benzathine, potassium, procaine, or sodium. Called also benzylpenicillin.
penicillin V a biosynthetically or semisynthetically produced antibiotic similar to penicillin g, used orally in the form of the benzathine or potassium salt for mild to moderately severe infections due to susceptible gram-positive bacteria.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pen·i·cil·lin G

a commonly used penicillin compound; it comprises 85% of the penicillin 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.
Farlex Partner Medical Dictionary © Farlex 2012


The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


Penicillin G. The original highly active penicillin. An antibiotic that remains useful although less effective than formerly against many strains of bacteria. It is inactivated by bacterial beta-lactamases. It is destroyed by the digestive system and must be given by injection. The drug is on the WHO official list.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
The affected sheep were treated with a single dose of 70,000IU of procaine benzylpenicillin and 70mg of dihydrostreptomycin sulfate, which is a low cost control method.
saprophyticus 2.103 28 4 16 ID AMP mecA PCG1 PCG MIC MIC SCL034 1 Neg 12 1 SCL041 1 Neg 12 1 SCL048 1 Neg 12 1 FOX30 = cefoxitin 30 [micro]g; FOXMIC = cefoxitin Etest; AMP2 = ampicillin 2 [micro]g; AMP MIC = ampicillin Etest; mecA = mecA status according to PCR; PCG1 = benzylpenicillin 1 unit; PCG MIC = benzylpenicillin Etest.
The strains of E.faecalis isolated (n = 12), which are facultative anaerobic Gram-positive cocci, were tested for their susceptibility/resistance to 12 antibiotics: benzylpenicillin, amoxicillin, amoxicillin + clavulanic acid, erythromycin, azithromycin, vancomycin, chloramphenicol, tetracycline, doxycycline, moxifloxacin, ciprofloxacin and rifampicin.
Ipai et al., "Single-dose azithromycin versus benzathine benzylpenicillin for treatment of yaws in children in Papua New Guinea: an open-label, non-inferiority, randomised trial," The Lancet, vol.
Before using the isolates in the in vitro assays, they were propagated on potato dextrose agar culture medium [PDA Difco[R] (Becton-Dickinson Company, Franklin Lakes, New Jersey, USA)] with 5 g L-1 of the antibiotic Pentabiotico[R] [benzylpenicillin benzathine, benzylpenicillin procaine, potassium benzylpenicillin, dihydrostreptomycin sulfate, streptomycin sulphate (Fort Dodge Saude Animal Ltda., Campinas, SP, Brazil)] and incubated in a growth chamber at 25 [+ or -] 1[degrees]C and a 12 h photoperiod.
The bag had medication in it which included aspirin, diazepam, adrenalin, salbutamol and benzylpenicillin. A prescription pad was also taken.
Monitoring of benzylpenicillin decomposition in gastric contents by capillary zone electrophoresis.
Pavel, "Raman and SERS investigations of potassium benzylpenicillin," Journal of Raman Spectroscopy, vol.
laidlawii PG8 cells were cultivated for 1 day at 37[degrees]C in Edward's medium (tryptose, 2% (w/v); NaCl, 0.5% (w/v); KCl, 0.13% (w/v); Tris base, 0.3% (w/v); serum of horse blood, 10% (w/v); fresh yeast extract, 5% (w/v); glucose solution, 1% (w/v); benzylpenicillin (500,000 IE [mL.sup.-1]), 0.2% (w/v)) to obtain the control cells.
The lack of penicillin metabolites (penicilloyl-polylysine and minor determinant mixture) could potentially be replaced by the soluble forms of the suspected beta-lactams or other beta-lactams from the same classes, along with benzylpenicillin and aminopenicillin, as skin test reagents since they are more easily available and have good predictive values in clinical practice [20].
to the ewe (600 mg Benzylpenicillin Sodium, Novartis Ltd, Auckland, New Zealand, 80 mg Gentamicin).