Antibiotics

Question 1

β-Lactams MOA

Answer 1

Cell wall synthesis inhibitor

• bactericidal
• highly reactive four member ring
• binds penicillin binding proteins (PBP)
  
  • =>prevents PBP from cross linking disaccharide chains
  • =>peptidoglycan layer can’t cross-link and stabilize
  • =>can’t form cell wall
• Subclasses
  
  • Penicillins
  • cephalosporins
  • carbapenems

Question 2

Glycopeptides MOA

Answer 2

Cell Wall synthesis inhibitors

• bactericidal
• binds peptidoglycan precursors
  
  • => PBP cannot crosslink
• ex. Vancomycin

Question 3

Macrolides MOA

Answer 3

Protein Synthesis Inhibitors

• bacteriostatic (cidal @ high concentrations)
• _binds and blocks 50s ribosomal subunit _
• large lactone ring w/ 1+ deoxy sugars attached
• good oral absorption
• “atypical” organism coverage
• ex. erythromycin, clanthromycin, azithromycin

Question 4

Lincosamides MOA

Answer 4

Protein Synthesis Inhibitors

• bacteriostatic
• good oral absorption
• has Chloride molecule => penetrates well into tissue (high lipophilicity)
• binds and blocks 50s ribosomal subunit
• turns off toxin production (TSST) in grp A strep and S. Aureus
• Ex. Clindamycin

Question 5

Aminoglycosides MOA

Answer 5

Protein Synthesis Inhibitors

• bacteriostatic (cidal at high concentrations)
• amino sugars linked together by glycosidic linkage
• binds 30s subunit
• poor oral absorption (IV only)
• high affinity for kidney/sensory cells
• Ex. gentamicin, tobramycin

Question 6

Tetracyclines MOA

Answer 6

Protein synthesis inhibitor

• bacteriostatic (cidal in some cases)
• 4 hydrocarbon ring structure
• good bioavailability orally
• poorly absorbed with food
• binds 30s subunit
• ex. doxycycline

Question 7

Sulfonamides

and

Trimethoprim

Answer 7

DNA Synthesis inhibitors

• ex. Septra
• bacteriostatic individually, bacteriocidal together

Sulfonamide:

• A sulfa drug!
• inhibits dihydropteroate synthetase (DHS) (binds active site)
  
  • in bacteria, not humans

Trimethoprim

• not a sulfa drug
• inhibits dihydrofolate reductase (DFR) (binds active site)
  
  • in humans and bacteria

Question 8

Flouroquinalones MOA

Answer 8

DNA synthesis inhibitors

• bacteriocidal??
• binds to and inhibits DNA gyrase (topoisomerase II) and topoisomerase IV
  
  • activation of apoptosis/cell death
• oral and IV, excellent bioavailability
• Ex. ciprofloxacin, levofloxacin

Question 9

Metranidazole MOA

Answer 9

DNA Synthesis inhibitors

• formation of free radicals… MOA poorly understood
• oral + IV, good bioavailability