1 / 21

Antimicrobial Drugs

Antimicrobial Drugs. How were antimicrobial drugs first discovered?. Alexander Fleming 1928 S. aureus, Penicillium notatum Mass production: 1940s Antibiosis Lead to antibiotic Different from chemotherapy!. Where do antibiotics come from?. From other bacteria found in Soil Bacteria

fergus
Download Presentation

Antimicrobial Drugs

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Antimicrobial Drugs

  2. How were antimicrobial drugs first discovered? • Alexander Fleming • 1928 • S. aureus, • Penicillium notatum • Mass production: 1940s • Antibiosis • Lead to antibiotic • Different from chemotherapy!

  3. Where do antibiotics come from? • From other bacteria found in • Soil • Bacteria • Streptomyces: more than half! • Bacillus • Molds • Penicillium • Cephalosporium

  4. What is an antibiotic’s spectrum? • Number/types of organisms it affects • Narrow spectrum of antibiotic activity • Penicillin G: mostly only gram + • Broad spectrum antibiotic activity • Tetracycline • Pros vs cons • Lead to superinfections

  5. How do antimicrobial drugs work? • Depends on the drug • Bactericidal or bacteristatic • Modes of action include • Cell wall destruction • Inhibiting transcription or translation • Plasma membrane damage • Inhibiting DNA synthesis • Inhibiting synthesis of metabolites

  6. How can an antibiotic destroy the cell wall? • Penicillin and others • Prevent synthesis (crosslinking) • Cell then lyses due to weakened wall • Only affects actively growing cells • Does not affect humans

  7. Can you discuss some examples? • Penicillin • Penicillin G • Narrow spectrum, penicillinase susceptible • Penicillinase-resistant penicillins • Methicillin • MRSA • Replacing methicillin: oxacillin, nafcillin • Extended spectrum penicillins • Ampicillin, amoxicillin • Effective against both gram + and – • Cephalosporins • Penicillinase resistant, gram – effective • Vancomycin • Narrow spectrum • Last resort

  8. How can they inhibit protein synthesis? • Tetracyclines, chloramphenicol, streptomycin, etc.

  9. How do they injure the PM? • Polypeptide antibiotics (e.g. polymyxin B) • Change permeability of PM

  10. How do they inhibit DNA synthesis? • Limited usefulness… WHY? • Quinolones • Inhibits DNA gyrase • UTIs • Fluoroquinolones • Ciprofloxacin (Cipro) • Affects cartilage development • Can be used in adults

  11. How do they inhibit synthesis of important metabolites? • Competitive inhibition • Synthetic drug • Sulfaniamide inhibits para-aminobenzoic acid (PABA) • PABA is precursor for making folic acid • Sulfa prevents conversion • Humans don’t make folic acid, we eat it! • Broad spectrum

  12. What are some antifungal drugs? • Many target fungal sterols • Ergosterol vs. (humans) cholesterol • Azoles • Athlete’s foot, yeast infection treatment • Others target chitin cell wall • Echinocandins • Many others which we won’t worry about…

  13. What about antiviral drugs? • Very few… WHY???? • Drugs can attack • Attachment • Penetration • Uncoating • DNA/RNA synthesis • Virion assembly

  14. Can you tell me about a couple? • Nucleosides and nucleotide analogs • Acyclovir: genital herpes • Interferons

  15. What tests are used to identify antimicrobial activity? • Disk-diffusion • Can’t determine bactericidal vs. stasis • Gradient diffusion • Broth dilution • Can determine bactericidal vs. -stasis

  16. Effects of Combinations of Drugs • Synergism occurs when the effect of two drugs together is greater than the effect of either alone • Antagonism occurs when the effect of two drugs together is less than the effect of either alone

  17. What’s next?

  18. Is there a downside to antimicrobial or antibiotic use? • Yes! • Natural selection • Antibiotics • Always take the full prescription • They don’t work on viruses!

  19. What types of resistance are there? • video • Destruction of the drug (e.g. penicillinase) • Prevention of drug penetration • Common with tetracycline • Alteration of drug target site • Rapid efflux • Heredity • Transformation, transduction, transposons

  20. Resistance to Antibiotics

  21. Future of Chemotherapeutic Agents • Antimicrobial peptides • Broad-spectrum antibiotics • Nisin (lactic acid bacteria) • Magainin (frogs) • Cecropin (moths) • Antisense agents • Complementary DNA that binds • a pathogen's virulence gene(s) • and prevents transcription • Fomivirsen to treat CMV retinitis • siRNA • Complementary RNA that binds mRNA to inhibit translation

More Related