Lecture 15

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mmorrow911
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2409
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Lecture 15
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2009-12-07 01:15:57
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Lecture 15 Antibiotics
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  1. Types of Antibiotic action against bacterial cells
    • Inhibition of bacterial cell wall synthesis
    • Alter permeability of bacterial cell membreane
    • Anti-metabolite avtivity - sulfer drugs
    • Inhibitioin of bacterial protein synthesis
    • Inhibition of bacterial necleic acid synthesis
  2. Who had the idea for "Magic Bullets"
    Paul Ehrlich
  3. Who found penicillin?
    Fleming
  4. Characteristics of the Ideal Antimicrobial Drug
    • Selectively toxic to the microbe but nontoxic to host cells
    • Microbicidal rather than microbistatic
    • Relatively soluble; functions even when highly diluted in body fluids
    • Remains potent long enough to act and is not broken down or excreted prematurly
    • Doesnt lead to the development of antimicrobial resistance
    • Complements or assist the activities of the hosts defenses
    • Remains active in tissues and body fluids
    • Readily delivered to the site of infection
    • Reasonably priced
    • Does not disrupt the hosts health by causing allergies or predisposing the host to other infections
  5. Chemotherapeutic drug
    Any chemical used in the treatment, relief, or prophlaxis of a disease
  6. Prophlaxis
    Use of a drug to prevent imminent infection of a person at risk
  7. Antimicrobial chemotherapy
    The use of chemotherapeutic drugs to control infection
  8. Antimicrobials
    All-inclusive term for any antimicrobial drug, regardless of its orgin
  9. Antibiotics
    Substances produced by the natural metabolic processes of some microorganisms that can inhibit or destroy other microorganisms
  10. Semisnthetic drugs
    Drugs which are chemically modified in the laboratory after being isolated from natural sources
  11. Synthetic drugs
    The use of chemical reactons of synthesize antimicrobial compounds in the labratory
  12. Narrow spectrum
    Antimicrobials effective against a limited array of micobial types
  13. Broad spectrum
    Antimicrobials effective against a wide variety of microbial types
  14. Naturally occuring antimicrobials
    • Metabolic products of bacteria and fungi
    • Reduce competition for nutrients and space

    Bacteria that produce them - Streptomyces, Bacillus, Escherichia

    Molds - Penicillium, Cephalosporium
  15. Antibiotics against Cell Wall Synthesis
    • Bacteriocidal
    • Penicillin and cephalosporins
    • - Binds and blocks peptidases involved in crosslinking the peptidoglycan molecules

    • Vancomycin
    • - Hinders peptidoglycan elongation

    • Cycloserine
    • - Inhibits the formation of the basic peptidoglycan subunits
  16. Antibiotics that target Protien Synthesis
    • Aminoglycosides
    • -Streptomycin, tetracycline, chloramphenicol
    • -Macrolides
    • - Erythromycin, Z-Pak
  17. Aminoglycosides
    • Bind to the 30s ribosomal subunits
    • Causes misreading of mRNA

    From Streptomyces spp.
  18. Tetracyclines
    Block attachment of tRNA
  19. Chloramphenicol
    • Bind to the 50s ribosomal subunit
    • Prevents peptide bond formation
  20. Examples of protein synthesis inhibitors
    • Tetracycline-
    • Broad spectrum and low cost
    • Commonly used to treat STD's

    • Erythromycin-
    • Broad spectrum
    • Commonly used as prophylactic drug prior to surgery

    • Chloramphenicol-
    • Broad spectrum
    • Treat typhoid fever, brain abcesses
    • Has a side effect of - Aplastic anemia
  21. Inhibitors of Nucleic Acid Synthesis
    • Rifamycin-
    • Inhibits RNA synthesis, Antituberculosis

    • Quinolones and fluoroquinolones-
    • Ciprofloxacin, Inhibits DNA gyrase, Urinary tract infections
  22. Folic acid synthesis
    • Sulfonamides (sulfa drugs) and trimthoprim-
    • Analogs, Completitive inhibition of enzymes, Prevents the metabolism of DNA, RNA and amino acid

    Works because mammals get folic acid from the diet and bacteria must make their own
  23. Antiviral
    • Increasing types of drugs becoming avaliable
    • Efective drugs - target viral replication cycle: Entry, Nucleic acid synthesis, Assembly and release
    • Interferon - genetically engineered aniviral protien from a human gene
  24. Other types of antimicrobials
    • Antifungal - Ketoconizole
    • Antiprotozoan- metronidazole (treat giardia)
    • Antimalarial - Quinine (treat malaria)
    • Anthihelminthic - mebendazole (treat tapeworms, roundworms)
  25. What factors promote antimicrobial resistance
    • Exposure to sub-optimal levels of antimicrobial
    • Inappropriate use
    • Exposure to microbes carrying resistance genes
  26. Inappropriate antimicrobial use
    • Prescription not taken correctly
    • Antibiotics for viral infections
    • Antibiotics sold without medical supervision
    • Spread of resistant microbes in hospitals due to lack of hygiene
    • Inadequate surveillance or defective susceptibility assays (giving drugs that are not effective)
    • Poverty or war
    • Use of antibiotics in food
  27. Tetracycline treatments
    Cause teeth dicoloration
  28. How to find an effective drug for treatment
    • Identify infectious agent - Culture
    • Perform sensitivity testing - Mueller Hinton agar
    • Often the minimum inhibitory concetration (MIC) is determined
  29. What test is used to determin the effectiveness of drug
    Kirby-Bauer Test
  30. Consequences of Antimicrobial Resistance
    • Infections resistant to avaliale antibiotics
    • Increased cost of treatment
  31. Proposals to combat antimicrobial resistance
    • Speed development of new antibiotics - fast track FDA
    • Track resistance data nationwide
    • Restrict antimicrobial use
    • Direct observed dosing (TB)
    • Use more narrow spectrum antibiotics
    • Use antimicrobial cocktails
  32. The future of chemotherapeutic agents
    Antimicrobial peptides - broad spectrum antibiotics from plants and animals

    Antisense agents- complementary DNA or peptide nucleic acids that binds to a pathogens virulence genes and prevents transcription

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