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Antimicrobial Drugs

Antimicrobial Drugs. The dawn of antibiotics. Paul Erlich (1910) Wanted to find the “magic bullet” for syphilis proposed the idea of the blood brain barrier Worked at staining tissues and first to come up with the idea behind “selective toxicity” Nobel Prize in 1908. Alexander Fleming.

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Antimicrobial Drugs

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  1. Antimicrobial Drugs

  2. The dawn of antibiotics • Paul Erlich (1910) • Wanted to find the “magic bullet” for syphilis • proposed the idea of the blood brain barrier • Worked at staining tissues and first to come up with the idea behind “selective toxicity” • Nobel Prize in 1908

  3. Alexander Fleming • A physician who studied bacterial action of blood and antisepsis • Discovered and named Lysozyme • Discovered mold growing on an agan plate(1928) • 1945 Nobel Prize in Physiology or Medicine along with Chain and Florey

  4. Chain and Florey • 1940 developed a system for growing Penicillium and purifying the drug • Tested the drug in mice, passed all trials • Received the Nobel Prize in 1945 with Alexander Fleming for their work

  5. Antibiotics • A substance produced by a microorganism that inhibits or kills other microbes

  6. Microbes that produce antibiotics

  7. Range of activity • Narrow range: target one group of microbes • Broad range: target a wide group of different microbes • Which one is the best?

  8. Spectrum of activity

  9. Targets of antimicrobial drugs

  10. Targets of Cell Wall Synthesis

  11. How does penicillin work? • Inhibits formation of tetrapeptide side chains….which means…. • What happens if you put a cell in a solution with penicillin?

  12. Some drugs target protein synthesis

  13. Penicillin weakens the cell wall

  14. Family tree of penicillins

  15. Beta-lactam ring common with penicillins and cephalosporins

  16. How organisms degrade penicillins

  17. Family of Penicillins • Natural penicillins • Penicillinase-resistant penicillins • Broad-spectrum penicillins • Extended-spectrum penicillins • Penicillins plus beta-lactamase inhibitors

  18. Side chain varies for derivatives of penicillin

  19. Cephalosporins • Derived from fungus, Acremonium cephalosporium • Chemical structure makes them resistant to beta-lactamase, low affinity for penicillin binding proteins • Grouped into first, second, third, and fourth generation cephalosporins

  20. Vancomycin • Binds to the terminal amino acids of the peptide chain of NAM molecules, blocks peptidoglycan formation

  21. Antibiotics that inhibit protein synthesis

  22. Aminoglycosides • Bactericidal • Irreversibly bind to 30S ribosome, cause misreading of the mRNA • Transported into cells that actively respire (not effective against ananerobes, streptococci, enterococci) • Ex: streptomycin, gentamicin, tobramycin

  23. Tetracyclines • Bind reversibly to 30S, block attachment of the tRNA to ribosome • Actively transported into bacterial cells • Effective against gram positive and gram negative • Resistance: due to decrease in uptake or increase in excretion • Ex: Doxycycline

  24. Macrolides • Reversibly bind to the 50S, prevent continuation of protein synthesis • Drug of choice for patients allergic to penicillins • Not good for Enterobacteriaceae • Ex: Erythromycin, Azithromycin • Resistance: enzymes that alter drug, decreased uptake

  25. Oxazolidinones • Reversibly bind to the 50S subunit, interfere with initiation of protein synthesis • Used for treating gram positive infections resistant to Beta-lactam drugs and Vancomycin • Ex: Linezolid

  26. Antibiotics that inhibit nucleic acid synthesis • Fluoroquinolones • Inhibit topoisomerase • Rifamycins • Blocks prokaryotic RNA polymerase from initiating transcription

  27. Antibiotics that inhibit metabolic pathways • Sulfonamides • Trimethoprims

  28. Sulfanilamide is structurally similar to PABA

  29. Sulfonamides (sulfa drugs) • First synthetic drugs to treat microbial infections • Used to treat urinary tract infections (UTIs) • Combination of trimethoprim and sulfamethoxazole (TMP-SMZ) example of synergism

  30. Drugs used together inhibit folic acid synthesis

  31. Tests for microbial sensitivity • Kirby-Bauer (disk diffusion method) • We did this in lab • Determining the Minimum Inhibitory Concentration (MIC) • E test • easier way to determine the MIC

  32. Kirby-Bauer tests for sensitivity

  33. Determining the Minimum Inhibitory Concentration (MIC)

  34. E-test for MIC

  35. What resistance looks like…

  36. Mechanisms of Drug resistance • Destruction or inactivation of the drug • Prevention of penetration to target site • Alteration of target site (mutation) • Pumping of the drug out of the bacterial cell

  37. Emerging Antibiotic Resistance • Enterococci • Staphylococcus aureus • Steptococcus pneumoniae • Mycobacterium tuberculosis

  38. Targets of Viral drugs

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