Ch 20 Antimicrobial drugs

  1. Who developed the concept of the magic bullet?
    Paul Ehrlich in early 1900s. Bullet kills only selected target (pathogen) and not the innocent bystander (host)
  2. What is the difference between an antibiotic, a semisynthetic, a synthetic, and an antimicrobial?
    Antibiotic is a medicine (such as penicillin or its derivatives) that inhibits the growth of or destroys microorganisms. A semisyntethic is (of a substance) made by synthesis from a naturally occurring material. And antimicrobial products kill or slow the spread of microorganisms. Microorganisms include bacteria, protozoans, and fungi such as mold and mildew.
  3. What is meant by selective toxicity?
    refers to the ability of antibiotics to selectively target bacterial cells yet have no toxicity towards human cells
  4. What is therapeutic index and how is it calculated? What ratio is favorable?
    • The maximum dose that is not toxic to the patient divided by minimum effective dose  against pathogen
    • Toxic does: 10mg/kg Effective dose 2mg/kg
    • TI=5 
    • High ratio=high TI=less toxic to patient. Penicillin TI=>10,000
  5. What is meant by spectrum of action? What is the difference between broad and narrow spectrum of action?
    An action spectrum is the rate of a physiological activity plotted against wavelength of light. It shows which wavelength of light is most effectively used in a specific chemical reaction. Some reactants are able to use specific wavelengths of light more effectively to complete their reactions

    Narrow:Drugs that affect a narrow range of microbial types.

    Broad:affect broad range of gram + or gram - bacteria.
  6. Why are drugs that target fungi often toxic to humans? Those that target Viruses? Those that target Helminths?
  7. When is antimicrobial susceptibility testing done?
    used to determine which specific antibiotics a particular bacteria or fungus is sensitive to. Most often, this testing complements a Gram stain and culture, the results of which are obtained much sooner.
  8. What are the 3 drug routes of administration? What are the advantages and disadvantages of each?
    Intramuscular, Intravenous, and oral.

    • Intramuscular is rapid but painful and expensive. May cause nerve damage. 
    • Intravenous has immediate action, but there is no retreat from it and it is more risky.
    • Oral is easy and cheap, but most orally administered drugs are absorbed slowly.
  9. What is the active portion of penicillin called? What does it do? What is penicillinase and how does it affect penicillin?
    • The twisted ring in the upper region is called the beta lactam ring; it is the active area of the penicillin molecule. 
    • It work by inhibiting bacterial cell wall biosynthesis.
    • Penicillinase resistant penicillins are antibiotics, which are not inactivated by thepenicillinase enzyme. Some bacteria produce the enzyme penicillinase that destroys the beta-lactam ring of the antibiotic, making the penicillin ineffective.
  10. What are the main bacterial cell targets of antimicrobial drugs?
    Two types of antimicrobial drugs work by inhibiting or interfering with cell wall synthesis of the target bacteria. Antibiotics commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cellsdo not have cell walls.
  11. What is antibiotic resistance? What are the 2 main ways in which resistance arises? What are the 5 specific ways in which resistance arises. Be able to give examples where applicable (if we talked about them).
    • Antibiotic resistance occurs when an antibiotic has lost its ability to effectively control or kill bacterial growth
    • Resistance genes:

    1.Antibiotic degrading enzymes

    2.Efflux pump (removes antibiotic from cell before harm occurs

    3.Antibiotic altering – chemically alters antibiotic

    Cell mutation event:

    1.Antibiotic is prevented from entering cell

    2.Target is altered (by mutation)
  12. What are the mechanisms of action of antiviral drugs?
    Isolation and sequencing of drug-resistant variants revealed single amino acid substitutions (I194M or D131V) in the VP1 capsid protein.
  13. Not counting antibiotic allergies, can a person ever become “immune” to an antibiotic so that it no longer works?
    No, it’s the bacteria that become genetically or metabolically resistant to the antibiotic
Card Set
Ch 20 Antimicrobial drugs
Microbio Chap 20 Antimicrobial drugs review questions