Penicillin

About: Penicillin is a research topic. Over the lifetime, 17916 publications have been published within this topic receiving 368480 citations. The topic is also known as: penicillin antibiotic & PCN.

Metabolism of Penicillins to Penicilloic Acids and 6-Aminopenicillanic Acid in Man and Its Significance in Assessing Penicillin Absorption

Abstract: Penicillins can be metabolized to penicilloic acids in man, the extent being dependent on the penicillin structure. In the phenoxy penicillin series, phenoxymethyl penicillin was found to be particularly unstable, but the higher homologues were more stable. In the isoxazolyl series, oxacillin was unstable, and progressive insertion of halogen in the phenyl ring increased stability. Ampicillin and amoxycillin showed some instability, ampicillin possibly being the more stable. After intramuscular administration, carbenicillin was very stable in the body, ampicillin was fairly stable, and benzyl penicillin was unstable. It is important to take into account the penicilloic acid content of urine when estimating total absorption of a penicillin. Increased stability in the body as well as slower renal clearance can lead to high concentrations in the serum. Penicilloic acids seemed to be more slowly cleared from the body than penicillins. The liver is probably the site of inactivation.

Susceptibility of group A beta-hemolytic streptococci to thirteen antibiotics: examination of 301 strains isolated in the United States between 1994 and 1997.

Abstract: Background. Because of continuing reports from many countries of increasing resistance of group A streptococci to macrolide antibiotics, we determined the antibiotic susceptibility of recent group A streptococcal isolates from the United States. Methods. We evaluated 301 Streptococcus pyogenes isolates (245 from patients with uncomplicated pharyngitis and 56 isolates from patients with invasive systemic infections) for susceptibility using the Etest technique. The isolates came from 24 states and the District of Columbia during the years 1994 through 1997. Thirteen antibiotics (azithromycin, ceftriaxone, cephalothin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, imipenem, levofloxacin, oxacillin, penicillin G, tetracycline and trimethoprim-sulfamethoxazole) were studied. Results. The MIC 90 for penicillin was 0.016 μg/ml, which is not significantly different from previous reports. Of the 301 isolates only 2.6% were resistant to a macrolide antibiotic and only 4% were resistant to tetracycline. Conclusions. These data indicate that antibiotic resistance among recent isolates of group A streptococci (including those from patients with severe infections) currently is not a clinically significant problem in the United States.

Cloning and heterologous expression of the penicillin biosynthetic gene cluster from penicillium chrysogenum

Abstract: A cosmid clone containing the putative penicillin biosynthetic gene cluster from Penicillium chrysogenum was used to transform the related filamentous fungi Neurospora crassa and Aspergillus niger, which do not produce beta-lactam antibiotics. Both of the transformed hosts contained intact P. chrysogenum DNA derived from the cosmid clone and produced authentic penicillin V. Assays of penicillin biosynthetic enzyme activity additionally demonstrated that they possessed delta-(L-alpha-amino-adipyl)-L-cysteinyl-D-valine synthetase (ACVS), isopenicillin N synthetase (IPNS) and acyl coenzyme A:6-aminopenicillanic acid acyltransferase (ACT) activity. The data suggests that genes encoding all the enzymes necessary for the biosynthesis of penicillin from amino acid precursors are closely linked in P. chrysogenum and constitute a gene cluster.

Mechanism of action of penicillin.

Abstract: \"The mechanism whereby penicillin exerts its cytotoxic effect remains obscure\" (Eagle and Saz, Ann. Rev. Microbiol., 9, 173, 1955) notwithstanding the universal use of this antibiotic in chemotherapy. However, there has been a concordance by many workers on the development of protoplasts or L-forms of bacteria (for review see Liebermeister and Kellenberger, Z. Naturforsch., 11, 200, 1956). These observations support the argument that penicillin inhibits cell-wall synthesis, and thereby provokes osmotic fragility in the excoriated bacteria (Cooper, Bacteriol. Revs., 20, 28, 1956). The argument may be illustrated with observations on Escherichia coli strain K-12 (Lederberg, Proc. Natl. Acad. Sci. U. S., 42, SM4, 1956 -where the point was not amplified). Cells actively growing in customary broth media will lyse after one to two hr exposure to penicillin. In a protective hypertonic medium, i. e., one supplemented with M/3 sucrose plus M/100 MgSO4, the treated cells do not lyse but instead they balloon into spherical \"protoplasts.\" Direct microscopic observations showed a one-for-one conversion of rods into protoplasts. The protoplast suspension is osmotically fragile and lyses when diluted into water or ordinary broth. In the protective medium, however, the protoplasts remain almost fully viable, and will revert to typical (colony-forming) rods when diluted in protective media lacking penicillin. Therefore, the bactericidal effect of penicillin in ordinary media is sufficiently explained by the induced osmotic fragility. As non-growing cells are not killed by penicillin, new wall-formation, rather than the existing wall, is the probable target. Lower concentrations of penicillin provoke the