Therapeutic Antimicrobials

Question 1

describe the differences between -cidal and -static drugs

Answer 1

Question 2

describe clinical situations when a broad-spectrum compound would be used

Answer 2

• wide differential diagnosis based on symptoms
• delay to wait for formal identification would be dangerous for patient
  
  • e.g. bacterial meningitis
• treatment of drug resistant pathogens where resistance is to narrow spectrum compounds
• polymicrobial infxns

Question 3

describe why it’s sometimes better to give multiple drugs

Answer 3

• to achieve a synergistic interaction
  
  • e.g. endocarditis caused by Enterococcus species:
  • exact combination can result in different effects
    
    • penicillin + gentamicin = bactericidal (kills)
    • penicillin alone = bacteriostatic (inhibits)
    • gentamicin alone = no sig. activity
• prevent or minimize development of resistance
  
  • e.g. tuberculosis, malaria
  • HIV: HAART (highly active antiretroviral therapy)
• extend antimicrobial spectrum

Question 4

describe the terms antagnostic, additive, synergistic and suppressive

Answer 4

Question 5

describe the inhibitors of metabolism

Answer 5

sulfonamides

• block folic acid synthesis (most bacteria)
• sulfonamides = structural analong of PABA = component of folic acid
  
  • basis for selective toxicity = no equivalent mammalian pathway
    
    • folic acid must be synthesized by bacteria

Question 6

describe the mechanism of action of sulfamethoxazole (SMX) and trimethoprim (TMP)

Answer 6

Question 7

describe inhibitors of protein synthesis

Answer 7

• higher binding affinity for prokaryotic ribosomes at level of:
  
  1. formation of 30s initiation complex
  2. formation of 70s ribosome
  3. elongation/assembly of amino acids

don’t need to know specific examples of the groups on chart

Question 8

summarize when antimicrobial drugs would be used

Answer 8