Antibiotics

Question 1

Time-dependent killers

Answer 1

Beta-lactams
Vancomycin

Bacterostatics: Tetracyclines
Macrolides
linezolid

Question 2

Concentration-dependent killers

Answer 2

aminoglycosides
quinolones
metronidazole

azithromycin (bacteriostatic)

Question 3

which two key drugs require TDM?

Answer 3

1. Aminoglycosides (ototoxicity and renal toxicity)
2. Vancomycin-treats MRSA

Question 4

Mechanism of resistance to antibiotics

Answer 4

Occurs when there is a lack of bacterial inhibition or killing at concentrations of antibiotics. Mechanisms:
1. Alter/ inactivate AB
2. Alter target site
3. Decreased entry
4. Increased efflux
5. Development of alt / bypass met pathways

Question 4

Mechanism of resistance to antibiotics

Answer 4

Occurs when there is a lack of bacterial inhibition or killing at concentrations of antibiotics. Mechanisms:
1. Alter/ inactivate AB
2. Alter target site
3. Decreased entry
4. Increased efflux
5. Development of alt / bypass met pathways

Question 5

Concentration versus time-dependent killing of organisms

Answer 5

MIC- minimum inhib concentration – lowest [drug] that prevents visible bact growth after 24h incubation in specified growth medium
Concentration dependent: increase bacterial killing as drug concentrations exceed MIC e.g. quinolones, aminoglycosides
Time dependent: kills bact when drug concentrations exceed MIC e.g. penicillins & cephalosporins

Question 6

Role of therapeutic monitoring, with particular reference to aminoglycosides and vancomycin

Answer 6

Aminoglycosides: toxic drugs with narrow TI
Nephrotoxicity and ototoxicity w/ prolonged use

Vancomycin (glycopeptide): narrow TI due to toxicity

Question 7

Mechanisms of Action of:
Beta Lactams
Macrolides
Nitromidazole derivatives
Tetracyclines
Aminoglycosides
Sulphonamides
Glycopeptides
Quinolones

Answer 7

Beta Lactams - Inhibit cell wall syn. [bactericidal]
Macrolides - Inhibit protein synthesis [bacteriostatic and bactericidal (at high conc)]
Nitroimidazole derivatives - disrupting the DNA of the susceptible bacteria and inhibiting the protein synthesis of the cell wall leading to cell death
Tetracyclines - inhibit bacterial protein synthesis [B.static]
Aminoglycosides -
Solphonamides - arrest cell growth by inhibiting bacteriual folic acid synthesis [B.static]
Glycopeptides - Inhibit cell wall synthesis - gram + only
Quinolones - Inhibit DNA gyrase and interfere with reproduction of Bacterial DNA [B.cidal]