General Principles Of Antimicrobial Therapy

Question 1

Antimicrobials are given as what types of therapy (5 types)

Answer 1

1. Prophylaxis - prevention
2. Pre-emptive therapy - no symptoms yet but px has alr been exposed to bug
3. Empirical - symptoms there, but unsure of what bug
4. Definitive - targeted AB, after culture results come out
5. Suppressive - infection not curative alr

Question 2

When should infective endocarditis prophylaxis be given?

Answer 2

Indicated b4 1. Certain dental procedures in pxs w 2. Underlying cardiac conditions

Dental procedures including
1. Manipulation of gingival tissue or periapical region of teeth
2. Perforation of oral mucosa

Underlying cardiac conditions such as:
1. Acquired valvular damage
2. Previous infective endocarditis
3. Structural congenital heart disease
4. Valve replacements (prosthetic valves)
5. Cardiomyopathy

Question 3

Infective endocarditis prophylaxis is contraindicated in pxs w:

Answer 3

1. Prosthetic joint implants
   - to prevent prosthetic joint infection
2. Wisdom tooth removal
   - double-blind randomized trials found that there was no significant difference in pain & post operative infections
   - adverse reactions to AB outweigh benefits of prophylxis

Question 4

Difference between Bactericidal and Bacteriostatic.

Answer 4

Bactericidal => kills bacteria at therapeutic doses
Bacteriostatic => arrest growth & replication at therapeutic conc., the anti-microbial doesnt eradicate the microbes, pxs immune response eliminates pathogens

Question 5

What are the 3 important determinants for successful antimicrobial therapy

Answer 5

1. Susceptibility testing, MIC
2. PK - what body does to drug, ADME
3. PD - what drug does to body, dosing schedule

Question 6

What are the 3 ways antimicrobial drugs can modulate microbial clearance in:

Answer 6

1. Time-dependent manner
   - rate & extent of microbe killing depends on duration conc spends above MIC
   - we want: smaller doses, given frequently
   - usually achieve conc 4x above MIC
2. Concentration-dependent manner
   - rate & extent of microbe killing depends on antimicrobial conc
   - large doses, less frequently
   - need drug conc to be 10x above MIC
3. Persistent post-antibiotic effect (PAE)

Question 7

What is the Post Antibiotic Effect (PAE)?

Answer 7

Suppression of microbial growth that persists after levels of antibiotic have fallen below MIC

• occurs bcuz microbes have been affected by AB, need time to overcome/regenerate b4 it can start growing again
• usually much longer in drugs that are conc-dependent, as compared to time-dependent drugs

Question 8

Combination therapy is less utilised than monotherapy to reduce toxicity and unnecessary damage to patients protective fungal n bacterial flora, when is it preferred?

Answer 8

1. Preventing resistance to monotherapy
2. Accelerating rapidity of microbial kill
3. Enhancing therapeutic efficacy by use of synergistic interactions
4. Paradoxically, reducing toxicity by administering lower doses (in cases of synergistic drugs)