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Antibacterial Inhibitors of Cell Wall Synthesis

Antibacterial Inhibitors of Cell Wall Synthesis. Very high therapeutic index Low toxicity with high effectiveness β - lactam Drugs Inhibit peptidoglycan synthesis Only effective against growing bacteria Vary in their spectrum of activity. Some bacteria produce β - lactamase enzymes

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Antibacterial Inhibitors of Cell Wall Synthesis

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  1. Antibacterial Inhibitors of Cell Wall Synthesis • Very high therapeutic index • Low toxicity with high effectiveness • β- lactam Drugs • Inhibit peptidoglycan synthesis • Only effective against growing bacteria • Vary in their spectrum of activity

  2. Some bacteria produce β- lactamase enzymes • Destroys β- lactam ring which inactivates drug • Greater variety produced by G- bacteria Penicillinasecleaves the β–lactam ring from the common nucleus of penicillin compounds

  3. Penicillins • group of over 50 related antibiotics • share a common core structure • Natural penicillins • have a narrow range of activity • Semisynthetic penicillins • overcome disadvantages

  4. Natural Penicillin • Produced by the mold Penicillium chrysogenum • Most common are Penicillin G and Penicillin V • Narrow spectrum • Effective against Gram + and few Gram – cocci

  5. Semi-synthetic Penicillin • Penicilinase-resistant penicillins • Methicillin – MRSA reduced use • Penicillins + -lactamase inhibitors • Augmentin • Combines amoxicillin with clavulanic acid which inhibits penicillinase

  6. Cephalosporins • Produced by mold Acremonium cephalosporium • resemble penicillin • broader spectrum • Semi-synthetic versions grouped as generations • New generations less susceptible to β -lactamases

  7. Polypeptide antibiotics • Bacitracin • Produced by species of Bacillus • Topical application due to toxicity • effective primarily against G+ bacteria

  8. Vancomycin • Produced by species of Streptomyces • Has narrow spectrum similar to penicillin • Used to treat antibiotic-associated colitis • Important "last line" against MRSA and VRE

  9. Antimycobacterial drugs • effective only against Mycobacterium • Isoniazid • Inhibits mycolic acid synthesis • Ethambutol • Inhibits incorporation of mycolic acid

  10. Antibacterial Inhibitors of Protein Synthesis • Bind 30S subunit • Aminoglycosides • Produced by Streptomyces spp. • Broad spectrum • Streptomycin, neomycin, gentamycin, tobramycin • serious side effects • Streptomycin is an alternative treatment for tuberculosis • resistant strains rapidly emerging

  11. Tetracyclines • Produced by Streptomyces • Oxytetracycline, Doxycycline • Broadest spectrum of all anti-bacterial drugs • Effective against most G- and G+ bacteria; rickettsias and chlamydias • Common animal feed additive

  12. Bind 50S subunit • Chloramphenicol • Produced by Streptomyces • Very simple chemical structure and inexpensive • Broad spectrum • Serious toxicity issues

  13. Macrolides • Erythromycin , azithromycin • Choice mycoplasmal pneumonia

  14. Oxazolidinones • Narrow spectrum (mostly G+), totally synthetic • resistance develops slower • Useful against vancomycin and β- lactam resistant bacteria

  15. Antibacterial Injury to the Plasma Membrane • Polymyxin B • Useful against G- bacteria & G+ • One of the 1st antibiotics useful against G- Pseudomonas • Topical • Combined with bacitracin and neomycin in over-the-counter preparation (neosporin)

  16. Antibacterial Inhibitors of Nucleic Acid Synthesis • Rifamycin • Rifampin • Inhibits RNA synthesis in prokaryotes • Effective against Gram+, Gram- and mycobacterium • Used in treatment of tuberculosis and prophylactic prevention of meningitis • Penetrate tissues so capable of reaching cerebrospinal fluid and abscesses

  17. Fluoroquinolones • Synthetic Drugs • Broad spectrum • Ciprofloxacin • Inhibits enzyme needed for DNA replication • Adversely effect the development of cartilage • limited use in children and pregnant women

  18. Antibacterial Anti-metabolites Sulfonamides (Sulfa drugs) • Broad spectrum • Inhibit folic acid synthesis Trimethoprim • Used in combination with sulfa drugs • broader spectrum and reduces the risk of resistance

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