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Penicillin and Cephalosprin: Beta-Lactam Antibiotics and Other Inhibitors of Cell Wall Synthesis

Penicillin and Cephalosprin: Beta-Lactam Antibiotics and Other Inhibitors of Cell Wall Synthesis. by Dena Nguyen http:www.denanguyen.tripod.com. OUTLINE. What are antibiotics? Bactericidal vs. bacteriostatic Broad spectrum vs. narrow spectrum What is peptidoglycan cell wall synthesis

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Penicillin and Cephalosprin: Beta-Lactam Antibiotics and Other Inhibitors of Cell Wall Synthesis

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  1. Penicillin and Cephalosprin: Beta-Lactam Antibiotics and Other Inhibitors of Cell Wall Synthesis by Dena Nguyen http:www.denanguyen.tripod.com

  2. OUTLINE • What are antibiotics? • Bactericidal vs. bacteriostatic • Broad spectrum vs. narrow spectrum • What is peptidoglycan cell wall synthesis • Structure of peptidoglycan cell wall • Peptidoglycan synthesis targeting the bacterial cell wall • How the drug will target the cell wall without harming us • General characteristics of Beta-Lactam antibiotics • General properties • Chemical structure • Mechanism of action • Resistance • Penicillin and Cephalosporin antibiotics affecting the cell wall synthesis • Original antibiotic derivate for this family • Chemical structure • Mechanism of action • Antibiotic spectrum of activity

  3. What Are Antibiotics? • Antibiotics: -Drugs that kill or inhibit growth of microorgansims by attacking a specific target Bactericidal: -eradicate an infection in absence of host defense mechanism Bacteriostatic: -inhibits microbial growth but requires host defense mechanisms to eradicate infection

  4. Narrow Spectrum -Specific for a small range of microorganisms Broad Spectrum -Effective against a wide range of microorganisms Selective Toxicity -More toxic to the invader than to the host -a property of useful antimicrobial drugs -for example: cell wall, ribosome, nucleus, and cell membrane

  5. How Does Synthesis of Cell Wall Peptidoglycan Occur? Peptidogylcan: - unique to procaryotes • provides rigid support for cell Composition: - murein backbone with peptide chain - N-acetylglucosamine- N-acetylmuramuric acid (NAG-NAM) - pentapeptide with L & D amino acids Peptidoglycan Synthesis: - 4 main steps - 3rd Amino Acid is an NH2 acid (lysine = gram + / diaminopimelic acid = gram -) - catalyzed by PBPs - (D-Ala-D-ala)

  6. Katzung, B. (2003): Basic and Clinical Pharmacology; McGraw-Hill, 9th edition.

  7. Antibiotics Affecting Cell Wall Synthesis

  8. General Characteristics of Beta-Lactam Antibiotics Chemical Structure: - beta-lactam ring w/ a neighboring ring Mechanism of action: - inhibit transpeptidation of peptidoglycan - effective on cell wall in actively growing bacterial cells Resistance: - Beta- lactamase activity • Katzung, B. (2003): Basic and Clinical Pharmacology; McGraw-Hill, 9th edition.

  9. Penicillin Prototype: - PCN G Chemical Structure: - 6-aminoepnicillanoic acid Mechanism of action: - binds to PBP Properties: - IM, IV, or orally - absorption of (most) oral pcns: 1) route of administration (except ex. amoxicillin) 2) drug-food interaction - large therapeutic range - distributed to tissues & renally excreted (most) - side effects are allergic rxns / anaphalyxis - cross – sensitivity to other pcns & cephalosporins - drug interaction w/ aminoglycosides

  10. Spectrum: 1) Penicillins(ex. PCN G) - active w/ gram +, gram - , & non-beta-lactamase producing anaerobes 2) Antistaphylococcal Penicillins (ex. Nafcillin) - active w/ staphylococci, streptococci - inactive w/ enterococci, anaerobes, gram – cocci & rods 3) Extended-Spectrum Penicillins (ex. Ampicillin) - active w/ most gram – • Katzung, B. (2003): Basic and Clinical Pharmacology; McGraw-Hill, 9th edition.

  11. Cephalosporins Protoype: - based on generation - not a pcn derivative Similar to penicillins: - chemically Mechanism of Action - toxicity/ therapeutic - (most) excretion via kidneys - cross- sensitivity - adverse rxn (allergic rxn) (plus: a disulfiram-like effect) Chemical Structure: - 7 aminocephalosporanic acid - R1 & R2 important properties - stable in pH & temperature changes - more stable to Beta-lactamase - (result) Broad Spectrum • Katzung, B. (2003): Basic and Clinical Pharmacology; McGraw-Hill, 9th edition.

  12. 4 Major Generations: 1st generation : ex) cephalexin , cephadrine 2nd generation : ex) cefamandole, cefaclor 3rd generation : ex) ceftriaxone, cefixime 4th generation : ex) cefipime

  13. Reference • www.mednet.odessa.ua/med/pharm/blactams.htm. • http://sprojects.mmimcgill.ca/antibiotic/bcwi.htm. • www.worldhistory.com/wiki/B/Beta-lactam-antibiotic.htm. • Katzung, B. (2003): Basic and Clinical Pharmacology; McGraw-Hill, 9th edition. • www.surfablebooks.com/wbmedical/32447/32531/2.htm. • www.cs.stedwards.edu/chem/Chemistry/CHEM43/CHEM43/Antibiotics/Antibiotics.html.

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