Principles of Antimicrobial Therapy

Question 1

What is the difference between an antibiotic and an antimicrobial?

Answer 1

Antibiotics are produced naturally by microorganisms to suppress growth or kill organisms
Antimicrobials include antibiotics and all synthetic preparations

Question 2

When should you use bacteriocidal agents?

Answer 2

Immunocompromised patients

Hard to reach areas of the host immune system

Question 3

What is required of the host when using bacteriostatic medications?

Answer 3

Host defense mechanisms must help to completely eliminate the infecting organisms

Question 4

What are common factors that affect the selection of antimicrobials?(8)

Answer 4

1. Patient allergies and cross-reactivity
2. Patient age (young/old=reduced metabolism and great risk for toxicity)
3. Pregnancy (cross the placenta and pose risk to fetus)
4. Host defense (compromised patients-transplant, AIDs, cancer)
5. ID of offending organism
6. Antimicrobial susceptibility
7. Pharmacokinetics
8. Anatomic site of infection

Question 5

What are benefits of prophylaxis?

Answer 5

Prevention of infection in patients who are: 
Immunocompromised 
Post-op (GI, oral, heart valve, joint)
Post spleen removal 
Recurrent UTIs

Question 6

What is the risk of prophylaxis?

Answer 6

Superinfection/Resistance

Toxicity

Question 7

What described an antibiotic combination that is indifferent?

Answer 7

Activity together equals the sum of separate independent activities
1+1=2

Question 8

What described an antibiotic combination that is synergistic?

Answer 8

Activity together is greater than the sum of the independent activities
1+1=3

Question 9

What described an antibiotic combination that is antagonistic?

Answer 9

Activity together is less than the sum of the independent activities
1+1=<1

Question 10

Two examples of combination antibiotics that have a synergistic effect are:

Answer 10

Sulfonamide/trimethoprim (Bactrim)

PCN with aminoglycosides

Question 11

What are common sites of antibacterial action in microorganisms? (4)

Answer 11

1. Inhibitor of metabolism
2. Inhibitors of cell wall synthesis
3. Inhibitors of protein synthesis
4. Inhibitors of nucleic acid function or synthesis

Question 12

Drugs that inhibit cellular metabolism also known as antimetabolites do what specifically and what is an example?

Answer 12

Completely inhibit PABA which causes an inhibition of folic acid.
Sulfonamides and trimethoprim
*G+/-

Question 13

Common drugs that inhibit cell wall synthesis:

Answer 13

B-lactams (PCN, cephalosporins)
Vancomycin
*G+

Question 14

Drugs that inhibit protein synthesis by targeting the 30S ribosomal subunit include:

Answer 14

Tetracyclines
Aminoglycosides CIDAL (gentamycin, tobramycin, neomycin, amikacin)
*G-

Question 15

Drugs that inhibit protein synthesis by targeting the 50S ribosomal subunit include:

Answer 15

Macrolides (erythromycin, clarithromycin, azythromycin
Lincosamides (clindamycin)
Chloramphenicol
*Some G+: clinda, EES, clarithro, atypicals:doxy and macrolides

Question 16

Drugs that inhibit protein synthesis by targeting the 70S ribosomal subunit include:

Answer 16

Linezolid (PO and IV)

*VRE (E. faecium, faecalis, MRSA

Question 17

Drugs that inhibit DNA gyrases include:

Answer 17

Fluroquinolones
Rifampin
*broad spectrum

Question 18

What are common drugs that are bacterostatic?

Answer 18

Tigecycline
Doxycycline
Azithromycin
Bactrim

Question 19

What are common drugs that are bacteriocidal?

Answer 19

Beta-lactams
Gentamicin 
Levofloxacin 
Nitrofurantoin 
Vancomycin